// SPDX-License-Identifier: MIT
//
// Query Linux system call names and numbers at runtime.
// Copyright (c) 2021  William Findlay
//
// June 14, 2021  William Findlay  Created this.

use std::collections::HashMap;
use std::env;
use std::fmt::Write as _;
use std::fs::File;
use std::io::Write as _;
use std::path::PathBuf;
use std::process::Command;

use csv::ReaderBuilder;
use glob::glob;

pub fn main() {
    println!("cargo:rerun-if-changed=syscalls-table");
    let syscalls = ingest();
    generate(&syscalls);
}

fn ingest() -> HashMap<String, HashMap<String, u64>> {
    let mut map: HashMap<String, HashMap<String, u64>> = HashMap::new();

    let mut csv_reader = ReaderBuilder::new();
    csv_reader
        .delimiter(b'\t')
        .trim(csv::Trim::Fields)
        .flexible(true);

    for table in glob("syscalls-table/tables/*")
        .expect("Failed to glob?!")
        .filter_map(Result::ok)
    {
        let syscalls = map
            .entry(
                table
                    .file_name()
                    .expect("No filename?!")
                    .to_str()
                    .expect("Invalid string?!")
                    .replace("syscalls-", ""),
            )
            .or_default();

        let mut reader = csv_reader
            .from_path(table)
            .expect("Failed to open table for reading");

        for record in reader.records().filter_map(Result::ok) {
            let name = record.get(0).expect("No syscall name?!");
            if let Some(number) = record.get(1).and_then(|n| n.parse::<u64>().ok()) {
                syscalls.insert(name.to_string(), number);
            }
        }
    }

    map
}

fn generate(syscalls: &HashMap<String, HashMap<String, u64>>) {
    let out_path = PathBuf::from(format!("{}/syscalls.rs", env::var("OUT_DIR").unwrap()));
    let mut out_str = String::new();

    write!(
        out_str,
        r#"
        use bimap::BiMap;
        use lazy_static::lazy_static;
        "#,
    )
    .unwrap();

    for (arch, syscalls) in syscalls {
        write!(
            out_str,
            r#"
            #[cfg(all(target_os = "linux", target_arch = "{arch}"))]
            lazy_static! {{
                pub static ref SYSCALL_NUMS: BiMap<&'static str, u64> = [
            "#,
            arch = arch,
        )
        .unwrap();
        for (name, number) in syscalls {
            write!(
                out_str,
                r#"
                    ("{name}", {number}),
                "#,
                name = name,
                number = number,
            )
            .unwrap();
        }
        write!(
            out_str,
            r#"
                ].iter().copied().collect();
            }}
            "#,
        )
        .unwrap();
    }

    File::create(&out_path)
        .expect("Failed to open syscalls.rs for writing")
        .write_all(&out_str.into_bytes())
        .expect("Failed to write to syscalls.rs");

    let status = Command::new("rustfmt")
        .arg(out_path)
        .status()
        .expect("Failed to run rustfmt");
    assert!(status.success());
}