use std::collections::BTreeMap;

use bytes::Bytes;
use http::header::CONTENT_ENCODING;
use http::header::CONTENT_LENGTH;
use http::header::CONTENT_TYPE;
use http::HeaderValue;
use tower::BoxError;

const FILE_CONFIG: &str = include_str!("../fixtures/file_upload/default.router.yaml");
const FILE_CONFIG_LARGE_LIMITS: &str = include_str!("../fixtures/file_upload/large.router.yaml");

/// Create a valid handler for the [helper::FileUploadTestServer].
macro_rules! make_handler {
    ($handler:expr) => {
        ::axum::Router::new().route("/", ::axum::routing::post($handler))
    };

    ($($path:literal => $handler:expr),+) => {
        ::axum::Router::new()
            $(.route($path, ::axum::routing::post($handler)))+
    }
}

#[tokio::test(flavor = "multi_thread")]
async fn it_uploads_a_single_file() -> Result<(), BoxError> {
    const FILE: &str = "Hello, world!";
    const FILE_NAME: &str = "example.txt";

    // Construct the parts of the multipart request as defined by the schema
    let request = helper::create_request(
        vec![FILE_NAME],
        vec![tokio_stream::once(Ok(Bytes::from_static(FILE.as_bytes())))],
    );

    // Run the test
    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG)
        .handler(make_handler!(helper::echo_single_file))
        .request(request)
        .subgraph_mapping("uploads", "/")
        .build()
        .run_test(|response| {
            insta::assert_json_snapshot!(response, @r###"
            {
              "data": {
                "file0": {
                  "filename": "example.txt",
                  "body": "Hello, world!"
                }
              }
            }
            "###);
        })
        .await
}

#[tokio::test(flavor = "multi_thread")]
async fn it_uploads_multiple_files() -> Result<(), BoxError> {
    let files = BTreeMap::from([
        ("example.txt", "Hello, world!"),
        ("example.json", r#"{ "message": "Hello, world!" }"#),
        (
            "example.yaml",
            "
            message: |
                Hello, world!
        "
            .trim(),
        ),
        (
            "example.toml",
            "
            [message]
            Hello, world!
        "
            .trim(),
        ),
    ]);

    // Construct the parts of the multipart request as defined by the schema for multiple files
    let request = helper::create_request(
        files.keys().cloned().collect::<Vec<_>>(),
        files
            .values()
            .map(|contents| tokio_stream::once(Ok(bytes::Bytes::from_static(contents.as_bytes()))))
            .collect::<Vec<_>>(),
    );

    // Run the test
    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG)
        .handler(make_handler!(helper::echo_files))
        .request(request)
        .subgraph_mapping("uploads", "/")
        .build()
        .run_test(move |response| {
            insta::assert_json_snapshot!(response, @r###"
            {
              "data": {
                "file0": {
                  "filename": "example.json",
                  "body": "{ \"message\": \"Hello, world!\" }"
                },
                "file1": {
                  "filename": "example.toml",
                  "body": "[message]\n            Hello, world!"
                },
                "file2": {
                  "filename": "example.txt",
                  "body": "Hello, world!"
                },
                "file3": {
                  "filename": "example.yaml",
                  "body": "message: |\n                Hello, world!"
                }
              }
            }
            "###);
        })
        .await
}

// TODO: This test takes ~3 minutes to complete. Possible solutions:
// - Lower the amount of data sent
// - Don't check that all of the bytes match
// TODO: Can we measure memory usage from within the test and ensure that it doesn't blow up?
#[tokio::test(flavor = "multi_thread")]
#[ignore]
async fn it_uploads_a_massive_file() -> Result<(), BoxError> {
    // Upload a stream of 10GB
    const ONE_MB: usize = 1024 * 1024;
    const TEN_GB: usize = 10 * 1024 * ONE_MB;
    const FILE_CHUNK: [u8; ONE_MB] = [0xAA; ONE_MB];
    const CHUNK_COUNT: usize = TEN_GB / ONE_MB;

    // Upload a file that is 1GB in size of 0xAA
    let file =
        tokio_stream::iter((0..CHUNK_COUNT).map(|_| Ok(bytes::Bytes::from_static(&FILE_CHUNK))));

    // Construct the parts of the multipart request as defined by the schema
    let request = helper::create_request(vec!["fat.payload.bin"], vec![file]);

    // Run the test
    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG_LARGE_LIMITS)
        .handler(make_handler!(helper::verify_stream).with_state((TEN_GB, 0xAA)))
        .request(request)
        .subgraph_mapping("uploads", "/")
        .build()
        .run_test(|response| {
            insta::assert_json_snapshot!(response, @r###"
            {
              "data": {
                "file0": {
                  "filename": "fat.payload.bin",
                  "body": "successfully verified all bytes as '0xAA'"
                }
              }
            }
            "###);
        })
        .await
}

#[tokio::test(flavor = "multi_thread")]
async fn it_uploads_to_multiple_subgraphs() -> Result<(), BoxError> {
    use reqwest::multipart::Form;
    use reqwest::multipart::Part;

    // Construct a manual multipart request with a valid file order
    let request = Form::new()
        .part(
            "operations",
            Part::text(
                serde_json::json!({
                    "query": "mutation SomeMutation($file0: Upload, $file1: UploadClone) {
                        file0: singleUpload(file: $file0) { filename body }
                        file1: singleUploadClone(file: $file1) { filename body }
                    }",
                    "variables": {
                        "file0": null,
                        "file1": null,
                    },
                })
                .to_string(),
            ),
        )
        .part(
            "map",
            Part::text(
                serde_json::json!({
                    "0": ["variables.file0"],
                    "1": ["variables.file1"],
                })
                .to_string(),
            ),
        )
        .part("0", Part::text("file0 contents").file_name("file0"))
        .part("1", Part::text("file1 contents").file_name("file1"));

    // Run the test
    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG)
        .handler(make_handler!(
            "/s1" => helper::echo_single_file,
            "/s2" => helper::echo_single_file
        ))
        .request(request)
        .subgraph_mapping("uploads", "/s1")
        .subgraph_mapping("uploads_clone", "/s2")
        .build()
        .run_test(|response| {
            insta::assert_json_snapshot!(response, @r###"
            {
              "data": {
                "file0": {
                  "filename": "file0",
                  "body": "file0 contents"
                },
                "file1": {
                  "filename": "file1",
                  "body": "file1 contents"
                }
              }
            }
            "###);
        })
        .await
}

#[tokio::test(flavor = "multi_thread")]
async fn it_supports_compression() -> Result<(), BoxError> {
    use reqwest::multipart::Form;

    const FILE_NAME: &str = "compressed.txt";
    const FILE_CONTENTS: &str = "compression saves space sometimes!";

    // We need to manually compress the body since reqwest does not yet support
    // compressing the initial request.
    // see: https://github.com/seanmonstar/reqwest/issues/1217
    fn compress(req: reqwest::Request) -> reqwest::Request {
        struct ManualRequest {
            boundary: String,
            body: Vec<u8>,
        }
        impl ManualRequest {
            fn new() -> Self {
                Self {
                    boundary: Form::new().boundary().to_string(),
                    body: Vec::new(),
                }
            }

            fn add_boundary(&mut self) {
                self.body
                    .extend(format!("--{}\r\n", self.boundary).as_bytes());
            }

            fn file(mut self, field_name: &str, file_name: &str, data: &str) -> Self {
                self.add_boundary();

                self.body.extend(format!("Content-Disposition: form-data; name=\"{field_name}\"; filename=\"{file_name}\"\r\n").as_bytes());
                self.body
                    .extend("Content-Type: text/plain\r\n\r\n".as_bytes());

                self.body.extend(data.as_bytes());
                self.body.extend("\r\n".as_bytes());

                self
            }

            fn text(mut self, field_name: &str, data: &str) -> Self {
                self.add_boundary();

                self.body.extend(
                    format!("Content-Disposition: form-data; name=\"{field_name}\"\r\n\r\n")
                        .as_bytes(),
                );

                self.body.extend(data.as_bytes());
                self.body.extend("\r\n".as_bytes());

                self
            }

            fn compress(mut self) -> (String, bytes::Bytes) {
                use std::io::Read;

                // Make sure to end the multipart stream
                self.body
                    .extend(format!("--{}--\r\n", self.boundary).as_bytes());

                // Values below are from the examples
                // see: https://github.com/dropbox/rust-brotli/blob/343beb46b8fd7864b22e5d1de4761d5716a29fa5/examples/compress.rs#L12
                let mut reader = brotli::CompressorReader::new(&self.body[..], 4096, 11, 22);
                let mut buf = Vec::new();

                reader
                    .read_to_end(&mut buf)
                    .expect("could not compress body");

                (self.boundary, bytes::Bytes::from(buf))
            }
        }

        let (boundary, request) = ManualRequest::new()
            .text(
                "operations",
                &serde_json::json!({
                    "query": "mutation SomeMutation($file0: Upload) {
                            file0: singleUpload(file: $file0) { filename body }
                        }",
                    "variables": {
                        "file0": null,
                    },
                })
                .to_string(),
            )
            .text(
                "map",
                &serde_json::json!({
                    "0": ["variables.file0"],
                })
                .to_string(),
            )
            .file("0", FILE_NAME, FILE_CONTENTS)
            .compress();

        // Fix some headers to account for compression
        let mut headers = req.headers().clone();
        headers.remove(CONTENT_LENGTH);
        headers.insert(
            CONTENT_ENCODING,
            reqwest::header::HeaderValue::from_static("br"),
        );
        headers.insert(
            CONTENT_TYPE,
            reqwest::header::HeaderValue::from_str(&format!(
                "multipart/form-data; boundary={boundary}"
            ))
            .unwrap(),
        );

        reqwest::Client::new()
            .post(req.url().clone())
            .headers(headers)
            .body(request)
            .build()
            .unwrap()
    }

    // Run the test
    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG)
        .handler(make_handler!(helper::echo_single_file))
        .request(Form::new()) // Gets overwritten by the `compress` transformer
        .subgraph_mapping("uploads", "/")
        .transformer(compress)
        .build()
        .run_test(|request| {
            insta::assert_json_snapshot!(request, @r###"
            {
              "data": {
                "file0": {
                  "filename": "compressed.txt",
                  "body": "compression saves space sometimes!"
                }
              }
            }
            "###);
        })
        .await
}

#[tokio::test(flavor = "multi_thread")]
async fn it_supports_non_nullable_file() -> Result<(), BoxError> {
    use reqwest::multipart::Form;
    use reqwest::multipart::Part;

    // Construct a manual request for non nullable checks
    let request = Form::new()
        .part(
            "operations",
            Part::text(
                serde_json::json!({
                    "query": "mutation SomeMutation($file0: Upload!) {
                        file0: singleUploadNonNull(file: $file0) { filename body }
                    }",
                    "variables": {
                        "file0": null,
                    },
                })
                .to_string(),
            ),
        )
        .part(
            "map",
            Part::text(
                serde_json::json!({
                    "0": ["variables.file0"],
                })
                .to_string(),
            ),
        )
        .part("0", Part::text("file0 contents").file_name("file0"));

    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG)
        .handler(make_handler!(helper::echo_single_file))
        .request(request)
        .subgraph_mapping("uploads", "/")
        .build()
        .run_test(|request| {
            insta::assert_json_snapshot!(request, @r###"
            {
              "data": {
                "file0": {
                  "filename": "file0",
                  "body": "file0 contents"
                }
              }
            }
            "###);
        })
        .await
}

#[tokio::test(flavor = "multi_thread")]
async fn it_supports_nested_file() -> Result<(), BoxError> {
    use reqwest::multipart::Form;
    use reqwest::multipart::Part;

    // Construct a manual request that sets up a nested structure containing a file to upload
    let request = Form::new()
        .part(
            "operations",
            Part::text(
                serde_json::json!({
                    "query": "mutation SomeMutation($file0: NestedUpload) {
                        file0: nestedUpload(nested: $file0) { filename body }
                    }",
                    "variables": {
                        "file0": {
                            "file": null,
                        },
                    },
                })
                .to_string(),
            ),
        )
        .part(
            "map",
            Part::text(
                serde_json::json!({
                    "0": ["variables.file0.file"],
                })
                .to_string(),
            ),
        )
        .part("0", Part::text("file0 contents").file_name("file0"));

    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG)
        .handler(make_handler!(helper::echo_single_file))
        .request(request)
        .subgraph_mapping("uploads", "/")
        .build()
        .run_test(|request| {
            insta::assert_json_snapshot!(request, @r###"
            {
              "data": {
                "file0": {
                  "filename": "file0",
                  "body": "file0 contents"
                }
              }
            }
            "###);
        })
        .await
}

#[tokio::test(flavor = "multi_thread")]
async fn it_supports_nested_file_list() -> Result<(), BoxError> {
    use reqwest::multipart::Form;
    use reqwest::multipart::Part;

    // Construct a manual request that sets up a nested structure containing a file to upload
    let request = Form::new()
        .part(
            "operations",
            Part::text(
                serde_json::json!({
                    "query": "mutation SomeMutation($files: [Upload!]!) {
                        files: multiUpload(files: $files) { filename body }
                    }",
                    "variables": {
                        "files": {
                            "0": null,
                            "1": null,
                            "2": null,
                        },
                    },
                })
                .to_string(),
            ),
        )
        .part(
            "map",
            Part::text(
                serde_json::json!({
                    "0": ["variables.files.0"],
                    "1": ["variables.files.1"],
                    "2": ["variables.files.2"],
                })
                .to_string(),
            ),
        )
        .part("0", Part::text("file0 contents").file_name("file0"))
        .part("1", Part::text("file1 contents").file_name("file1"))
        .part("2", Part::text("file2 contents").file_name("file2"));

    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG)
        .handler(make_handler!(helper::echo_file_list))
        .request(request)
        .subgraph_mapping("uploads", "/")
        .build()
        .run_test(|request| {
            insta::assert_json_snapshot!(request, @r###"
            {
              "data": {
                "files": [
                  {
                    "filename": "file0",
                    "body": "file0 contents"
                  },
                  {
                    "filename": "file1",
                    "body": "file1 contents"
                  },
                  {
                    "filename": "file2",
                    "body": "file2 contents"
                  }
                ]
              }
            }
            "###);
        })
        .await
}

#[tokio::test(flavor = "multi_thread")]
async fn it_fails_upload_without_file() -> Result<(), BoxError> {
    // Construct a request with no attached files
    let request = helper::create_request(vec!["missing.txt"], Vec::<tokio_stream::Once<_>>::new());

    // Run the test
    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG)
        .handler(make_handler!(helper::always_fail))
        .request(request)
        .subgraph_mapping("uploads", "/")
        .build()
        .run_test(|response| {
            insta::assert_json_snapshot!(response, @r###"
            {
              "errors": [
                {
                  "message": "HTTP fetch failed from 'uploads': HTTP fetch failed from 'uploads': error from user's HttpBody stream: error reading a body from connection: Missing files in the request: '0'.",
                  "path": [],
                  "extensions": {
                    "code": "SUBREQUEST_HTTP_ERROR",
                    "service": "uploads",
                    "reason": "HTTP fetch failed from 'uploads': error from user's HttpBody stream: error reading a body from connection: Missing files in the request: '0'."
                  }
                }
              ]
            }
            "###);
        })
        .await
}

#[tokio::test(flavor = "multi_thread")]
async fn it_fails_with_file_count_limits() -> Result<(), BoxError> {
    // Create a list of files that passes the limit set in the config (5)
    let files = (0..100).map(|index| index.to_string());

    // Construct the parts of the multipart request as defined by the schema for multiple files
    let request = helper::create_request(
        files.clone().collect::<Vec<_>>(),
        files
            .map(|_| tokio_stream::once(Ok(bytes::Bytes::new())))
            .collect::<Vec<_>>(),
    );

    // Run the test
    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG)
        .handler(make_handler!(helper::always_fail))
        .request(request)
        .subgraph_mapping("uploads", "/")
        .build()
        .run_test(|response| {
            insta::assert_json_snapshot!(response, @r###"
            {
              "errors": [
                {
                  "message": "Exceeded the limit of 5 file uploads of files in a single request.",
                  "extensions": {
                    "code": "FILE_UPLOADS_LIMITS_MAX_FILES_EXCEEDED"
                  }
                }
              ]
            }
            "###);
        })
        .await
}

#[tokio::test(flavor = "multi_thread")]
async fn it_fails_with_file_size_limit() -> Result<(), BoxError> {
    // Create a file that passes the limit set in the config (512KB)
    const ONE_MB: usize = 1024 * 1024;
    const FILE_CHUNK: [u8; ONE_MB] = [0xAA; ONE_MB];

    // Construct the parts of the multipart request as defined by the schema for multiple files
    let request = helper::create_request(
        vec!["fat.payload.bin"],
        vec![tokio_stream::once(Ok(bytes::Bytes::from_static(
            &FILE_CHUNK,
        )))],
    );

    // Run the test
    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG)
        .handler(make_handler!(helper::always_fail))
        .request(request)
        .subgraph_mapping("uploads", "/")
        .build()
        .run_test(|response| {
            insta::assert_json_snapshot!(response, @r###"
            {
              "errors": [
                {
                  "message": "HTTP fetch failed from 'uploads': HTTP fetch failed from 'uploads': error from user's HttpBody stream: error reading a body from connection: Exceeded the limit of 512.0 KB on 'fat.payload.bin' file.",
                  "path": [],
                  "extensions": {
                    "code": "SUBREQUEST_HTTP_ERROR",
                    "service": "uploads",
                    "reason": "HTTP fetch failed from 'uploads': error from user's HttpBody stream: error reading a body from connection: Exceeded the limit of 512.0 KB on 'fat.payload.bin' file."
                  }
                }
              ]
            }
            "###);
        })
        .await
}

#[tokio::test(flavor = "multi_thread")]
async fn it_fails_invalid_multipart_order() -> Result<(), BoxError> {
    use reqwest::multipart::Form;
    use reqwest::multipart::Part;

    // Construct a manual multipart request out of order
    // Note: The order is wrong, but the parts follow the spec
    let request = Form::new()
        .part(
            "map",
            Part::text(serde_json::json!({
                "0": ["variables.file0"]
            }).to_string()),
        ).part(
            "operations",
            Part::text(serde_json::json!({
                "query": "mutation ($file0: Upload) { singleUpload(file: $file0) { filename } }",
                "variables": {
                    "file0": null,
                },
            }).to_string())
        ).part("0", Part::text("file contents").file_name("file0"));

    // Run the test
    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG)
        .handler(make_handler!(helper::always_fail))
        .request(request)
        .subgraph_mapping("uploads", "/")
        .build()
        .run_test(|response| {
            insta::assert_json_snapshot!(response, @r###"
            {
              "errors": [
                {
                  "message": "Missing multipart field 'operations', it should be a first field in request body.",
                  "extensions": {
                    "code": "FILE_UPLOADS_OPERATION_CANNOT_STREAM"
                  }
                }
              ]
            }
            "###);
        })
        .await
}

#[tokio::test(flavor = "multi_thread")]
async fn it_fails_invalid_file_order() -> Result<(), BoxError> {
    use reqwest::multipart::Form;
    use reqwest::multipart::Part;

    // Construct a manual multipart request with files out of order
    let request = Form::new()
        .part(
            "operations",
            Part::text(
                serde_json::json!({
                    "query": "mutation ($file0: Upload, $file1: UploadClone) {
                        file0: singleUpload(file: $file0) { filename body }
                        file1: singleUploadClone(file: $file1) { filename body }
                    }",
                    "variables": {
                        "file0": null,
                        "file1": null,
                    },
                })
                .to_string(),
            ),
        )
        .part(
            "map",
            Part::text(
                serde_json::json!({
                    "0": ["variables.file0"],
                    "1": ["variables.file1"],
                })
                .to_string(),
            ),
        )
        .part("1", Part::text("file1 contents").file_name("file1"))
        .part("0", Part::text("file0 contents").file_name("file0"));

    // Run the test
    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG)
        .handler(make_handler!(
            "/s1" => helper::echo_single_file,
            "/s2" => helper::always_fail
        ))
        .request(request)
        .subgraph_mapping("uploads", "/s1")
        .subgraph_mapping("uploads_clone", "/s2")
        .build()
        .run_test(|response| {
            insta::assert_json_snapshot!(response, @r###"
            {
              "data": {
                "file0": {
                  "filename": "file0",
                  "body": "file0 contents"
                },
                "file1": null
              },
              "errors": [
                {
                  "message": "HTTP fetch failed from 'uploads_clone': HTTP fetch failed from 'uploads_clone': error from user's HttpBody stream: error reading a body from connection: Missing files in the request: '1'.",
                  "path": [],
                  "extensions": {
                    "code": "SUBREQUEST_HTTP_ERROR",
                    "service": "uploads_clone",
                    "reason": "HTTP fetch failed from 'uploads_clone': error from user's HttpBody stream: error reading a body from connection: Missing files in the request: '1'."
                  }
                }
              ]
            }
            "###);
        })
        .await
}

#[tokio::test(flavor = "multi_thread")]
async fn it_fails_with_no_boundary_in_multipart() -> Result<(), BoxError> {
    // Create multipart request and remove the boundary
    let request = helper::create_request(
        Vec::<&str>::new(),
        Vec::<tokio_stream::Once<hyper::Result<bytes::Bytes>>>::new(),
    );

    // Remove the boundary from the request to fail
    fn strip_boundary(mut req: reqwest::Request) -> reqwest::Request {
        req.headers_mut().insert(
            CONTENT_TYPE,
            HeaderValue::from_static("multipart/form-data"),
        );

        req
    }

    // Run the test
    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG)
        .handler(make_handler!(helper::always_fail))
        .request(request)
        .subgraph_mapping("uploads", "/")
        .transformer(strip_boundary)
        .build()
        .run_test(|response| {
            insta::assert_json_snapshot!(response, @r###"
            {
              "errors": [
                {
                  "message": "invalid multipart request: multipart boundary not found in Content-Type",
                  "extensions": {
                    "code": "FILE_UPLOADS_OPERATION_CANNOT_STREAM"
                  }
                }
              ]
            }
            "###);
        })
        .await
}

#[tokio::test(flavor = "multi_thread")]
async fn it_fails_incompatible_query_order() -> Result<(), BoxError> {
    use reqwest::multipart::Form;
    use reqwest::multipart::Part;

    // Construct a manual multipart request with an impossible file order
    // Note: With the `stream` mode of file upload this order is impossible since
    // the second file needs to be processed first
    let request = Form::new()
        .part(
            "operations",
            Part::text(
                serde_json::json!({
                    "query": "mutation SomeMutation($file0: UploadClone, $file1: Upload) {
                        file1: singleUpload(file: $file1) { filename }
                        file0: singleUploadClone(file: $file0) { filename }
                    }",
                    "variables": {
                        "file0": null,
                        "file1": null,
                    },
                })
                .to_string(),
            ),
        )
        .part(
            "map",
            Part::text(
                serde_json::json!({
                    "0": ["variables.file0"],
                    "1": ["variables.file1"],
                })
                .to_string(),
            ),
        )
        .part("0", Part::text("file0 contents").file_name("file0"))
        .part("1", Part::text("file1 contents").file_name("file1"));

    // Run the test
    helper::FileUploadTestServer::builder()
        .config(FILE_CONFIG)
        .handler(make_handler!(
            "/s1" => helper::always_fail,
            "/s2" => helper::always_fail
        ))
        .request(request)
        .subgraph_mapping("uploads", "/s1")
        .subgraph_mapping("uploads_clone", "/s2")
        .build()
        .run_test(|response| {
            insta::assert_json_snapshot!(response, @r###"
            {
              "errors": [
                {
                  "message": "References to variables containing files are ordered in the way that prevent streaming of files.",
                  "extensions": {
                    "code": "FILE_UPLOADS_OPERATION_CANNOT_STREAM"
                  }
                }
              ]
            }
            "###);
        })
        .await
}

mod helper {
    use std::collections::BTreeMap;
    use std::collections::HashMap;
    use std::net::IpAddr;
    use std::net::Ipv4Addr;
    use std::net::SocketAddr;
    use std::path::PathBuf;

    use axum::extract::State;
    use axum::response::IntoResponse;
    use axum::BoxError;
    use axum::Json;
    use axum::Router;
    use buildstructor::buildstructor;
    use futures::StreamExt;
    use http::header::CONTENT_TYPE;
    use http::Request;
    use http::StatusCode;
    use hyper::Body;
    use itertools::Itertools;
    use multer::Multipart;
    use reqwest::multipart::Form;
    use reqwest::multipart::Part;
    use serde::de::DeserializeOwned;
    use serde::Deserialize;
    use serde::Serialize;
    use serde_json::json;
    use serde_json::Value;
    use thiserror::Error;
    use tokio::net::TcpListener;
    use tokio_stream::Stream;

    use super::super::common::IntegrationTest;

    /// A helper server for testing multipart uploads.
    ///
    /// Note: This is a shim until wiremock supports two needed features:
    /// - [Streaming of the body](https://github.com/LukeMathWalker/wiremock-rs/pull/133)
    /// - [Async handlers for responders](https://github.com/LukeMathWalker/wiremock-rs/issues/84)
    ///
    /// Another alternative is to treat the handler (a [Router]) as a tower service and just [tower::ServiceExt::oneshot] it,
    /// but since the integration test is running the router as a normal process, we don't have a nice way to
    /// do so without running the HTTP server.
    pub struct FileUploadTestServer {
        config: &'static str,
        handler: Router,
        request: Form,
        subgraph_mappings: HashMap<String, String>,
        transformer: Option<fn(reqwest::Request) -> reqwest::Request>,
    }

    #[buildstructor]
    impl FileUploadTestServer {
        /// Create a test server with the supplied config, handler and request.
        ///
        /// Prefer the builder so that tests are more descriptive.
        ///
        /// See [make_handler] and [create_request].
        #[builder]
        pub fn new(
            config: &'static str,
            handler: Router,
            subgraph_mappings: HashMap<String, String>,
            request: Form,
            transformer: Option<fn(reqwest::Request) -> reqwest::Request>,
        ) -> Self {
            Self {
                config,
                handler,
                request,
                subgraph_mappings,
                transformer,
            }
        }

        /// Runs a test, using the provided validation_fn to ensure that the response matches
        /// what is expected.
        pub async fn run_test(
            self,
            validation_fn: impl Fn(uhg_custom_appollo_roouter::graphql::Response),
        ) -> Result<(), BoxError> {
            // Ensure that we have the test keys before running
            // Note: The [IntegrationTest] ensures that these test credentials get
            // set before running the router.
            if std::env::var("TEST_APOLLO_KEY").is_err()
                || std::env::var("TEST_APOLLO_GRAPH_REF").is_err()
            {
                return Ok(());
            };

            // Bind to the first available port
            let addr = SocketAddr::new(IpAddr::V4(Ipv4Addr::new(127, 0, 0, 1)), 0);
            let bound = TcpListener::bind(addr).await.unwrap();
            let bound_url = bound.local_addr().unwrap();
            let bound_url = format!("http://{bound_url}");

            // Set up the router with the custom subgraph handler above
            let mut router = IntegrationTest::builder()
                .config(self.config)
                .subgraph_overrides(
                    self.subgraph_mappings
                        .into_iter()
                        .map(|(name, path)| (name, format!("{bound_url}{path}")))
                        .collect(),
                )
                .supergraph(PathBuf::from_iter([
                    "tests",
                    "fixtures",
                    "file_upload",
                    "schema.graphql",
                ]))
                .build()
                .await;

            router.start().await;
            router.assert_started().await;

            // Have a way to shutdown the server once the test finishes
            let (shutdown_tx, shutdown_rx) = tokio::sync::oneshot::channel::<()>();

            // Start the server using the tcp listener randomly assigned above
            let server = axum::Server::from_tcp(bound.into_std().unwrap())
                .unwrap()
                .serve(self.handler.into_make_service())
                .with_graceful_shutdown(async {
                    shutdown_rx.await.ok();
                });

            // Spawn the server in the background, controlled by the shutdown signal
            tokio::spawn(server);

            // Make the request and pass it into the validator callback
            let (_span, response) = router
                .execute_multipart_request(self.request, self.transformer)
                .await;
            let response = serde_json::from_slice(&response.bytes().await?)?;
            validation_fn(response);

            // Kill the server and finish up
            shutdown_tx.send(()).unwrap();
            Ok(())
        }
    }

    /// A valid response from the file upload GraphQL schema
    #[derive(Serialize, Deserialize)]
    pub struct Upload {
        pub filename: Option<String>,
        pub body: Option<String>,
    }

    #[derive(Serialize, Deserialize)]
    pub struct Operation {
        // TODO: Can we verify that this is a valid graphql query?
        query: String,
        variables: BTreeMap<String, Value>,
    }

    #[derive(Error, Debug)]
    pub enum FileUploadError {
        #[error("bad headers in request: {0}")]
        BadHeaders(String),

        #[error("required field is empty: {0}")]
        EmptyField(String),

        #[error("invalid data received in multipart message: {0}")]
        InvalidData(#[from] serde_json::Error),

        #[error("invalid multipart request: {0}")]
        InvalidMultipart(#[from] multer::Error),

        #[error("expected a file with name '{0}' but found nothing")]
        MissingFile(String),

        #[error("expected a list of files but found nothing")]
        MissingList,

        #[error("expected a set of mappings but found nothing")]
        MissingMapping,

        #[error("expected request to fail, but subgraph received data")]
        ShouldHaveFailed,

        #[error("stream ended prematurely, expected {0} bytes but found {1}")]
        StreamEnded(usize, usize),

        #[error("stream returned unexpected data: expected {0} but found {1}")]
        UnexpectedData(u8, u8),

        #[error("unexpected field: expected '{0}' but got '{1:?}'")]
        UnexpectedField(String, Option<String>),

        #[error("expected end of stream but found a file")]
        UnexpectedFile,

        #[error("mismatch between supplied variables and mappings: {0} != {1}")]
        VariableMismatch(usize, usize),
    }

    impl IntoResponse for FileUploadError {
        fn into_response(self) -> axum::response::Response {
            let error = uhg_custom_appollo_roouter::graphql::Error::builder()
                .message(self.to_string().as_str())
                .extension_code("FILE_UPLOAD_ERROR") // Without this line, the error cannot be built...
                .build();
            let response = uhg_custom_appollo_roouter::graphql::Response::builder()
                .error(error)
                .build();

            (StatusCode::BAD_REQUEST, Json(json!(response))).into_response()
        }
    }

    /// Creates a valid multipart request out of a list of files
    pub fn create_request(
        names: Vec<impl Into<String>>,
        files: Vec<impl Stream<Item = hyper::Result<bytes::Bytes>> + Send + 'static>,
    ) -> reqwest::multipart::Form {
        // Each of the below text fields is generated from the supplied list of files, so we need to construct
        // each specially in order to match the shape defined in the test schema.
        // TODO: Can we use the [graphql_client::GraphQLQuery] trait to construct this for us?

        // Operations needs to contain file upload mutations with each file specified as an argument, followed
        // by a list of variables that map the subsequent parts of the multipart stream to the mutation placeholders.
        let operations = Part::text(
            serde_json::json!({
                "query": format!(
                    "mutation ({args}) {{ {queries} }}",
                    args = names.iter().enumerate().map(|(index, _)| format!("$file{index}: Upload")).join(", "),
                    queries = names.iter().enumerate().map(|(index, _)| format!("file{index}: singleUpload(file: $file{index}) {{ filename body }}")).join(" "),
                ),
                "variables": names.iter().enumerate().map(|(index, _)| (format!("file{index}"), serde_json::Value::Null)).collect::<BTreeMap<String, serde_json::Value>>(),
            })
            .to_string(),
        )
        .file_name("operations.graphql");

        // The mappings match the field names of the multipart stream to the graphql variables of the query
        let mappings = Part::text(
            serde_json::json!(names
                .iter()
                .enumerate()
                .map(|(index, _)| (index.to_string(), vec![format!("variables.file{index}")]))
                .collect::<BTreeMap<String, Vec<String>>>())
            .to_string(),
        )
        .file_name("mappings.json");

        // The rest of the request are the file streams
        let mut request = reqwest::multipart::Form::new()
            .part("operations", operations)
            .part("map", mappings);
        for (index, (file_name, file)) in names.into_iter().zip(files).enumerate() {
            let file_name: String = file_name.into();
            let part = Part::stream(hyper::Body::wrap_stream(file)).file_name(file_name);

            request = request.part(index.to_string(), part);
        }

        request
    }

    /// Handler that echos back the contents of the file that it receives
    ///
    /// Note: This will error if more than one file is received
    pub async fn echo_single_file(
        mut request: Request<Body>,
    ) -> Result<Json<Value>, FileUploadError> {
        let (_, map, mut multipart) = decode_request(&mut request).await?;

        // Assert that we only have 1 file
        if map.len() > 1 {
            return Err(FileUploadError::UnexpectedFile);
        }

        let field_name: String = map
            .into_keys()
            .take(1)
            .next()
            .ok_or(FileUploadError::MissingMapping)?;

        // Extract the single expected file
        let upload = {
            let f = multipart
                .next_field()
                .await?
                .ok_or(FileUploadError::MissingFile(field_name.clone()))?;

            let file_name = f.file_name().unwrap_or(&field_name).to_string();
            let body = f.bytes().await?;

            Upload {
                filename: Some(file_name),
                body: Some(String::from_utf8_lossy(&body).to_string()),
            }
        };

        let alias = format!("file{field_name}");
        Ok(Json(json!({
            "data": {
                alias: upload,
            }
        })))
    }

    /// Handler that echos back the contents of the files that it receives
    pub async fn echo_files(mut request: Request<Body>) -> Result<Json<Value>, FileUploadError> {
        let (operation, map, mut multipart) = decode_request(&mut request).await?;

        // Make sure that we have some mappings
        if map.is_empty() {
            return Err(FileUploadError::MissingMapping);
        }

        // Make sure that we have an equal number of mappings and variables
        if map.len() != operation.variables.len() {
            return Err(FileUploadError::VariableMismatch(
                map.len(),
                operation.variables.len(),
            ));
        }

        // Extract all of the files
        let mut files = BTreeMap::new();
        for (file_mapping, var_mapping) in map.into_iter() {
            let f = multipart
                .next_field()
                .await?
                .ok_or(FileUploadError::MissingFile(file_mapping.clone()))?;

            let field_name = f
                .name()
                .and_then(|name| (name == file_mapping).then_some(name))
                .ok_or(FileUploadError::UnexpectedField(
                    file_mapping,
                    f.name().map(String::from),
                ))?;
            let file_name = f.file_name().unwrap_or(field_name).to_string();
            let body = f.bytes().await?;

            // TODO: This is a bit hard-coded, but it should be enough for testing the whole plugin stack
            // The shape of the variables list for tests should always be ["variables.<NAME_OF_FILE>"]
            let var_name = var_mapping.first().ok_or(FileUploadError::MissingMapping)?;
            let var_name = var_name.split('.').nth(1).unwrap().to_string();

            files.insert(
                var_name,
                Upload {
                    filename: Some(file_name),
                    body: Some(String::from_utf8_lossy(&body).to_string()),
                },
            );
        }

        Ok(Json(json!({
            "data": files
        })))
    }

    /// Handler that echos back the contents of the list of files that it receives
    pub async fn echo_file_list(
        mut request: Request<Body>,
    ) -> Result<Json<Value>, FileUploadError> {
        let (operation, map, mut multipart) = decode_request(&mut request).await?;

        // Make sure that we have some mappings
        if map.is_empty() {
            return Err(FileUploadError::MissingMapping);
        }

        // Make sure that we have one list input
        let file_list = {
            let Some((_, list)) = operation.variables.first_key_value() else {
                return Err(FileUploadError::MissingList);
            };

            let Some(list) = list.as_object() else {
                return Err(FileUploadError::MissingList);
            };

            list
        };

        // Make sure that the list has the correct amount of slots for the files
        if file_list.len() != map.len() {
            return Err(FileUploadError::VariableMismatch(
                map.len(),
                file_list.len(),
            ));
        }

        // Extract all of the files
        let mut files = Vec::new();
        for file_mapping in map.into_keys() {
            let f = multipart
                .next_field()
                .await?
                .ok_or(FileUploadError::MissingFile(file_mapping.clone()))?;

            let field_name = f
                .name()
                .and_then(|name| (name == file_mapping).then_some(name))
                .ok_or(FileUploadError::UnexpectedField(
                    file_mapping,
                    f.name().map(String::from),
                ))?;
            let file_name = f.file_name().unwrap_or(field_name).to_string();
            let body = f.bytes().await?;

            files.push(Upload {
                filename: Some(file_name),
                body: Some(String::from_utf8_lossy(&body).to_string()),
            });
        }

        Ok(Json(json!({
            "data": {
                "files": files,
            },
        })))
    }

    /// A handler that always fails. Useful for tests that should not reach the subgraph at all.
    pub async fn always_fail(mut request: Request<Body>) -> Result<Json<Value>, FileUploadError> {
        // Consume the stream
        while request.body_mut().next().await.is_some() {}

        // Signal a failure
        Err(FileUploadError::ShouldHaveFailed)
    }

    /// Verifies that a file stream is present and goes to completion
    ///
    /// Note: Make sure to use a router with state (Expected stream length, expected value).
    pub async fn verify_stream(
        State((expected_length, byte_value)): State<(usize, u8)>,
        mut request: Request<Body>,
    ) -> Result<Json<Value>, FileUploadError> {
        let (_, _, mut multipart) = decode_request(&mut request).await?;

        let mut file = multipart
            .next_field()
            .await?
            .ok_or(FileUploadError::MissingFile("verification stream".into()))?;
        let file_name = file.file_name().unwrap_or("file0").to_string();

        let mut count = 0;
        while let Some(chunk) = file.chunk().await? {
            // Keep track of how many bytes we've seen
            count += chunk.len();

            // Make sure that the bytes match what is expected
            let unexpected = match chunk.into_iter().all_equal_value() {
                Ok(value) => (value != byte_value).then_some(value),
                Err(Some((lhs, rhs))) => {
                    if lhs != byte_value {
                        Some(lhs)
                    } else {
                        Some(rhs)
                    }
                }
                Err(None) => None,
            };
            if let Some(unexpected_byte) = unexpected {
                return Err(FileUploadError::UnexpectedData(byte_value, unexpected_byte));
            }
        }

        // Make sure we've read the expected amount of bytes
        if count != expected_length {
            return Err(FileUploadError::StreamEnded(expected_length, count));
        }

        // A successful response means that the stream was valid
        Ok(Json(json!({
            "data": {
                "file0": Upload {
                    filename: Some(file_name),
                    body: Some(format!("successfully verified all bytes as '{byte_value:#X}'")),
                }
            }
        })))
    }

    /// Extract a field from a multipart request and validate it
    async fn extract_field<'short, 'a: 'short, T: DeserializeOwned>(
        mp: &'short mut Multipart<'a>,
        field_name: &str,
    ) -> Result<T, FileUploadError> {
        let field = mp
            .next_field()
            .await?
            .ok_or(FileUploadError::EmptyField(field_name.into()))?;

        // Verify that the field is named as expected
        if field.name() != Some(field_name) {
            return Err(FileUploadError::UnexpectedField(
                field_name.into(),
                field.name().map(String::from),
            ));
        }

        // Deserialize the response
        let bytes = field.bytes().await?;
        let result = serde_json::from_slice::<T>(&bytes)?;

        Ok(result)
    }

    /// Decodes a raw request into a GraphQL file upload multipart message.
    ///
    /// Note: This performs validation checks as well.
    /// Note: The order of the mapping must correspond with the order in the request, so
    /// we use a [BTreeMap] here to keep the order when traversing the list of files.
    async fn decode_request(
        request: &mut Request<Body>,
    ) -> Result<(Operation, BTreeMap<String, Vec<String>>, Multipart), FileUploadError> {
        let content_type = request
            .headers()
            .get(CONTENT_TYPE)
            .ok_or(FileUploadError::BadHeaders("missing content_type".into()))?;

        let boundary = multer::parse_boundary(content_type.to_str().map_err(|e| {
            FileUploadError::BadHeaders(format!("could not parse multipart boundary: {e}"))
        })?)?;

        let mut multipart = Multipart::new(request.body_mut(), boundary);

        // Extract the operations
        // TODO: Should we be streaming here?
        let operations: Operation = extract_field(&mut multipart, "operations").await?;
        let map: BTreeMap<String, Vec<String>> = extract_field(&mut multipart, "map").await?;

        Ok((operations, map, multipart))
    }
}