use std::collections::BTreeMap;
use std::env;
use std::fs;
use std::path::{Path, PathBuf};
use std::process::{Command, Stdio};

fn main() {
    println!("cargo:rerun-if-changed=build.rs");
    for watched in [
        "src",
        "index.html",
        "vite.config.ts",
        "package.json",
        "bun.lock",
        "tsconfig.json",
        "tsconfig.app.json",
        "tsconfig.node.json",
    ] {
        println!("cargo:rerun-if-changed={watched}");
    }

    let root = PathBuf::from(env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR"));
    let out_dir = PathBuf::from(env::var("OUT_DIR").expect("OUT_DIR"));

    if env::var_os("ADMIN_UI_SKIP_FRONTEND_BUILD").is_none() && !build_frontend(&root) {
        println!(
            "cargo:warning=admin frontend build via bun/npm unavailable or failed; \
             embedding existing dist/ as-is"
        );
    }

    let dist = root.join("dist");
    let index = dist.join("index.html");
    if !index.is_file() {
        panic!(
            "dist/index.html not found — run `bun install && bun run build` \
             (or `npm run build`) inside admin/ first"
        );
    }

    let mut files: BTreeMap<String, PathBuf> = BTreeMap::new();
    collect(&dist, &dist, &mut files);

    let mut src = String::from("// @generated by build.rs — embedded admin frontend (dist/)\n\n");
    src.push_str(&format!("pub const INDEX: &[u8] = include_bytes!({:?});\n\n", index));
    src.push_str("pub const FILES: &[(&str, &[u8])] = &[\n");
    for (rel, abs) in &files {
        if rel == "index.html" {
            continue;
        }
        src.push_str(&format!("    ({:?}, include_bytes!({:?})),\n", rel, abs));
    }
    src.push_str("];\n\npub const PATHS: &[&str] = &[\n");
    for rel in files.keys() {
        src.push_str(&format!("    {:?},\n", rel));
    }
    src.push_str("];\n");

    fs::write(out_dir.join("dist_embed.rs"), src).expect("write dist_embed.rs");
}

fn build_frontend(root: &Path) -> bool {
    if !root.join("package.json").is_file() {
        return false;
    }
    let tool = if command_ok("bun") {
        "bun"
    } else if command_ok("npm") {
        npm_cmd()
    } else {
        return false;
    };

    let mut steps: Vec<(&str, &[&str])> = Vec::new();
    if !root.join("node_modules").is_dir() {
        steps.push((tool, &["install"]));
    }
    steps.push((tool, &["run", "build"]));

    for (t, args) in steps {
        eprintln!("cargo:warning=running `{t} {}` in {}", args.join(" "), root.display());
        let ok = Command::new(t)
            .args(args)
            .current_dir(root)
            .status()
            .map(|s| s.success())
            .unwrap_or(false);
        if !ok {
            return false;
        }
    }
    true
}

#[cfg(windows)]
fn npm_cmd() -> &'static str {
    "npm.cmd"
}
#[cfg(not(windows))]
fn npm_cmd() -> &'static str {
    "npm"
}

fn command_ok(name: &str) -> bool {
    Command::new(name)
        .arg("--version")
        .stdin(Stdio::null())
        .stdout(Stdio::null())
        .stderr(Stdio::null())
        .status()
        .is_ok_and(|s| s.success())
}

fn collect(base: &Path, dir: &Path, out: &mut BTreeMap<String, PathBuf>) {
    for entry in fs::read_dir(dir).expect("read dist dir") {
        let path = entry.expect("dist entry").path();
        if path.is_dir() {
            collect(base, &path, out);
        } else {
            let rel = path
                .strip_prefix(base)
                .unwrap()
                .to_string_lossy()
                .replace('\\', "/");
            out.insert(rel, path);
        }
    }
}