use std::env;
use std::fs;
use std::io::prelude::*;
use std::io::BufReader;
use std::iter::FromIterator;
use std::path::Path;
use std::string::String;

extern crate bindgen;

fn gen_syscall() -> Result<String, Box<dyn std::error::Error>> {
    let mut buf = String::new();
    for entry in Path::new("syscall-tables").read_dir()? {
        let p = entry?.path();
        let filename = if let Some(f) = p.file_name() {
            f
        } else {
            continue;
        };
        let arch = if let Some(a) = filename
            .to_string_lossy()
            .into_owned()
            .strip_suffix("_table.h")
        {
            a.to_string()
        } else {
            continue;
        };
        buf.push_str("{ let mut t = HashMap::new(); for (num, name) in &[");

        // Entries look like
        //     _S(0, "io_setup")
        // Just get rid of the _S.
        let defs = BufReader::new(fs::File::open(p)?)
            .lines()
            .filter(|line| line.as_ref().unwrap().starts_with("_S("))
            .map(|line| line.unwrap())
            .map(|line| line.strip_prefix("_S").unwrap().to_string());
        for def in defs {
            buf.push_str(def.as_str());
            buf.push(',');
        }
        buf.push_str("] { t.insert(*num, *name); } ");
        buf.push_str(format!(" hm.insert(\"{arch}\", t); }}\n").as_str());
    }
    Ok(buf)
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let out_dir = env::var_os("OUT_DIR").unwrap();
    let dest_path = Path::new(&out_dir).join("const.rs");
    let msg_file = "audit-specs/messages/message-dictionary.csv";
    let fields_file = "audit-specs/fields/field-dictionary.csv";

    let mut constants: Vec<(String, String)> = BufReader::new(fs::File::open(msg_file)?)
        .lines()
        .skip(1) // skip over header
        .map(|line| {
            line.unwrap()
                .split(',')
                .map(|x| x.to_string())
                .collect::<Vec<_>>()
        })
        .map(|fields| {
            (
                fields[0].strip_prefix("AUDIT_").unwrap().to_string(),
                fields[1].clone(),
            )
        })
        .collect();

    // Artificial record
    constants.push(("CONTAINER_INFO".into(), "0xffffff01".into()));

    let fields: Vec<(String, String)> = BufReader::new(fs::File::open(fields_file)?)
        .lines()
        .skip(3) // skip over heder and regex describing a* mess
        .map(|line| {
            line.unwrap()
                .split(',')
                .map(|x| x.to_string())
                .collect::<Vec<_>>()
        })
        .map(|fields| (fields[0].clone(), fields[1].clone()))
        .collect();

    let mut template = Vec::new();
    fs::File::open("src/const.rs.in")?.read_to_end(&mut template)?;
    let template = String::from_utf8(template)?;

    let buf = template
        .replace(
            "/* @EVENT_CONST@ */",
            &String::from_iter(
                constants
                    .iter()
                    .map(|(name, value)| format!(r#"("{name}", {value}), "#)),
            ),
        )
        .replace(
            "/* @FIELD_TYPES@ */",
            &String::from_iter(
                fields
                    .iter()
                    .filter(|(_, typ)| typ == "encoded" || typ.starts_with("numeric"))
                    .map(|(name, typ)| match typ.as_str() {
                        "numeric hexadecimal" => format!(r#"("{name}", FieldType::NumericHex),"#),
                        "numeric decimal" => format!(r#"("{name}", FieldType::NumericDec),"#),
                        "numeric octal" => format!(r#"("{name}", FieldType::NumericOct),"#),
                        "numeric" => format!(r#"("{name}", FieldType::Numeric),"#),
                        "encoded" => format!(r#"("{name}", FieldType::Encoded),"#),
                        _ => format!(r#"("{name}", FieldType::Invalid),"#),
                    }),
            ),
        )
        .replace(
            "/* @CONSTANTS@ */",
            &String::from_iter(constants.iter().map(|(name, value)| {
                format!(
                    "#[allow(dead_code)] pub const {name}: MessageType = MessageType({value});\n",
                )
            })),
        )
        .replace("/* @SYSCALL_BUILD@ */", &gen_syscall()?)
        .into_bytes();

    fs::write(dest_path, buf)?;

    #[cfg(target_os = "linux")]
    bindgen::Builder::default()
        .header("src/sockaddr.h")
        .rust_target(bindgen::RustTarget::Stable_1_47)
        .allowlist_type("^sockaddr_.*")
        .allowlist_var("^AF_.*")
        .layout_tests(false)
        .generate()
        .expect("unable to generate bindings")
        .write_to_file(std::path::PathBuf::from(env::var("OUT_DIR").unwrap()).join("sockaddr.rs"))
        .expect("Couldn't write bindings!");

    println!("cargo:rerun-if-changed=build.rs");
    println!("cargo:rerun-if-changed=const.rs.in");
    #[cfg(target_os = "linux")]
    println!("cargo:rerun-if-changed=src/sockaddr.h");
    println!("cargo:rerun-if-changed={msg_file}");
    println!("cargo:rerun-if-changed={fields_file}");

    Ok(())
}