//! Build extensible language packs and pinned, authenticated Swagger UI assets.
use serde_json::{json, Value};
use std::{collections::HashSet, env, fs, path::PathBuf, process::Command};

// Prepare the actual embedded bytes here, not in a dependency's earlier build.
// Cargo config discovery is deliberately irrelevant to the pinned default.
fn swagger_assets(
    root: &std::path::Path,
    out: &std::path::Path,
) -> Result<(), Box<dyn std::error::Error>> {
    for name in [
        "SWAGGER_UI_DOWNLOAD_URL",
        "SWAGGER_UI_ARCHIVE_SHA256",
        "RUST_PROXY_PYTHON",
        "CARGO_NET_OFFLINE",
    ] {
        println!("cargo:rerun-if-env-changed={name}");
    }
    let helper = root.join("scripts/swagger_assets.py");
    println!("cargo:rerun-if-changed={}", helper.display());
    let interpreters = match env::var_os("RUST_PROXY_PYTHON") {
        Some(value) if !value.is_empty() => vec![value],
        _ => vec!["python3".into(), "python".into()],
    };
    for interpreter in interpreters {
        match Command::new(&interpreter).arg(&helper).arg("--out-dir").arg(out).status() {
            Ok(status) if status.success() => return Ok(()),
            Ok(_) => return Err("Swagger UI asset preparation failed; see the diagnostic above and docs/API_ACCESS.md".into()),
            Err(error) if error.kind() == std::io::ErrorKind::NotFound => continue,
            Err(error) => return Err(error.into()),
        }
    }
    Err("Python 3.10+ is required for build assets; install python3 or set RUST_PROXY_PYTHON to its executable".into())
}

fn main() -> Result<(), Box<dyn std::error::Error>> {
    let root = PathBuf::from(
        env::var_os("CARGO_MANIFEST_DIR").ok_or("Cargo did not supply CARGO_MANIFEST_DIR")?,
    );
    let out = PathBuf::from(env::var_os("OUT_DIR").ok_or("Cargo did not supply OUT_DIR")?);
    swagger_assets(&root, &out)?;
    let langs = root.join("langs");
    println!("cargo:rerun-if-changed={}", langs.display());
    let mut paths: Vec<_> = fs::read_dir(&langs)
        .expect("langs directory is required")
        .map(|entry| entry.expect("read language entry").path())
        .filter(|path| path.extension().is_some_and(|ext| ext == "json"))
        .collect();
    paths.sort();
    assert!(
        !paths.is_empty() && paths.len() <= 128,
        "expected 1..128 language packs"
    );
    let mut languages = Vec::new();
    let mut locales = HashSet::new();
    for path in paths {
        println!("cargo:rerun-if-changed={}", path.display());
        let id = path
            .file_stem()
            .unwrap()
            .to_str()
            .expect("language filename must be UTF-8");
        assert!(
            id.len() <= 64
                && id
                    .bytes()
                    .all(|b| b.is_ascii_alphanumeric() || b == b'_' || b == b'-'),
            "invalid language filename: {}",
            path.display()
        );
        let content = fs::read(&path).expect("read language JSON");
        assert!(content.len() <= 262_144, "language pack exceeds 256 KiB");
        let pack: Value =
            serde_json::from_slice(&content).unwrap_or_else(|e| panic!("{}: {e}", path.display()));
        let meta = pack["meta"]
            .as_object()
            .expect("language meta object is required");
        for key in ["locale", "name", "native_name", "direction"] {
            assert!(
                meta.get(key)
                    .and_then(Value::as_str)
                    .is_some_and(|v| !v.is_empty() && v.len() <= 128),
                "{id}: missing/invalid {key}"
            );
        }
        assert!(
            matches!(meta["direction"].as_str(), Some("ltr" | "rtl")),
            "{id}: invalid direction"
        );
        let locale = meta["locale"].as_str().unwrap();
        assert!(
            locale.split('-').all(|part| !part.is_empty()
                && part.len() <= 8
                && part.bytes().all(|b| b.is_ascii_alphanumeric())),
            "{id}: use a BCP-47 style locale"
        );
        assert!(
            locales.insert(locale.to_ascii_lowercase()),
            "duplicate locale {locale}"
        );
        let translations = pack["translations"]
            .as_object()
            .expect("translations object is required");
        assert!(
            translations.len() <= 4096
                && translations.iter().all(|(k, v)| !k.is_empty()
                    && k.len() <= 128
                    && v.as_str().is_some_and(|s| s.len() <= 16_384)),
            "{id}: translations must be bounded strings"
        );
        languages.push(json!({"id":id,"meta":meta,"translations":translations}));
    }
    assert!(
        languages.iter().any(|p| p["id"] == "en_US"),
        "en_US.json is the required fallback pack"
    );
    let login_path = root.join("src/admin/web/login-keys.json");
    println!("cargo:rerun-if-changed={}", login_path.display());
    let login_keys: HashSet<String> =
        serde_json::from_slice(&fs::read(login_path).expect("read public translation keys"))
            .expect("parse public translation keys");
    let mut login_languages = languages.clone();
    for language in &mut login_languages {
        language["translations"]
            .as_object_mut()
            .expect("translations object")
            .retain(|key, _| login_keys.contains(key));
    }
    let login_bundle =
        serde_json::to_vec(&json!({"default":"en_US","languages":login_languages})).unwrap();
    fs::write(out.join("login-langs.json"), login_bundle).expect("write login translations");
    let bundle = serde_json::to_vec(&json!({"default":"en_US","languages":languages})).unwrap();
    assert!(bundle.len() <= 8_388_608, "language bundle exceeds 8 MiB");
    fs::write(out.join("langs.json"), bundle).expect("write language bundle");
    Ok(())
}