use std::{
    env, fs,
    path::{Path, PathBuf},
};

fn content_hash(content: &str) -> String {
    let value = content.bytes().fold(0xcbf29ce484222325_u64, |hash, byte| {
        (hash ^ u64::from(byte)).wrapping_mul(0x100000001b3)
    });
    format!("{value:016x}")
}

fn write_asset(output: &Path, stem: &str, extension: &str, content: &str) -> String {
    let file_name = format!("{stem}.{}.{extension}", content_hash(content));
    fs::write(output.join(&file_name), content)
        .unwrap_or_else(|error| panic!("write {file_name}: {error}"));
    file_name
}

fn cargo_asset_env(name: &str, file_name: &str) {
    println!("cargo:rustc-env={name}_FILE={file_name}");
    println!("cargo:rustc-env={name}_ROUTE=/assets/{file_name}");
}

fn main() {
    let output = PathBuf::from(env::var_os("OUT_DIR").expect("OUT_DIR"));
    println!("cargo:rerun-if-changed=build.rs");
    println!("cargo:rerun-if-changed=web");
    println!("cargo:rerun-if-changed=docs/api-ui");
    println!("cargo:rerun-if-changed=vendor/swagger-ui/swagger-ui-bundle.js");
    println!("cargo:rerun-if-changed=vendor/swagger-ui/swagger-ui.css");

    if let Ok(entries) = fs::read_dir(&output) {
        for entry in entries.flatten() {
            let name = entry.file_name();
            let name = name.to_string_lossy();
            let generated_asset = (name.starts_with("app.") || name.starts_with("docs."))
                && (name.ends_with(".js") || name.ends_with(".css"));
            if generated_asset {
                let _ = fs::remove_file(entry.path());
            }
        }
    }

    let manifest = fs::read_to_string("web/assets.list").expect("web/assets.list is required");
    let mut js =
        String::from("/* MikroTik Backup System 0.0.1; generated from web/assets.list */\n");
    let mut css = String::new();
    for entry in manifest
        .lines()
        .map(str::trim)
        .filter(|value| !value.is_empty() && !value.starts_with('#'))
    {
        let source = fs::read_to_string(PathBuf::from("web").join(entry))
            .unwrap_or_else(|error| panic!("{entry}: {error}"));
        if entry.ends_with(".js") {
            js.push_str(&source);
            js.push_str("\n;\n");
        } else if entry.ends_with(".css") {
            css.push_str(&source);
            css.push('\n');
        } else {
            panic!("Unsupported bundle input: {entry}");
        }
    }

    let app_js_file = write_asset(&output, "app", "js", &js);
    let app_css_file = write_asset(&output, "app", "css", &css);
    cargo_asset_env("APP_JS", &app_js_file);
    cargo_asset_env("APP_CSS", &app_css_file);

    let html = fs::read_to_string("web/index.html")
        .expect("web/index.html is required")
        .replace("/assets/app.js", &format!("/assets/{app_js_file}"))
        .replace("/assets/app.css", &format!("/assets/{app_css_file}"));
    fs::write(output.join("index.html"), html).expect("write HTML shell");

    let mut docs_js = fs::read_to_string("vendor/swagger-ui/swagger-ui-bundle.js")
        .expect("Swagger UI JavaScript is required")
        .lines()
        .filter(|line| !line.starts_with("//# sourceMappingURL="))
        .collect::<Vec<_>>()
        .join("\n");
    docs_js.push_str("\n;\n");
    docs_js.push_str(&fs::read_to_string("docs/api-ui/init.js").expect("docs API initializer"));

    let mut docs_css = fs::read_to_string("vendor/swagger-ui/swagger-ui.css")
        .expect("Swagger UI stylesheet is required")
        .replace("/*# sourceMappingURL=swagger-ui.css.map*/", "");
    docs_css.push('\n');
    docs_css.push_str(&fs::read_to_string("docs/api-ui/style.css").expect("docs API stylesheet"));

    let docs_js_file = write_asset(&output, "docs", "js", &docs_js);
    let docs_css_file = write_asset(&output, "docs", "css", &docs_css);
    cargo_asset_env("DOCS_JS", &docs_js_file);
    cargo_asset_env("DOCS_CSS", &docs_css_file);

    let docs_html = fs::read_to_string("docs/api-ui/index.html")
        .expect("docs API HTML is required")
        .replace("/assets/docs.js", &format!("/assets/{docs_js_file}"))
        .replace("/assets/docs.css", &format!("/assets/{docs_css_file}"));
    fs::write(output.join("docs.html"), docs_html).expect("write API documentation HTML");
}