package main

import (
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net/http"
	"os"
	"path/filepath"
	"sync"
)

// Asset directories, relative to project root.
const (
	jsDir  = "assets/js"
	cssDir = "assets/css"
)

// files maps download URLs to local destination paths.
var files = map[string]string{
	"https://raw.githubusercontent.com/starfederation/datastar/main/bundles/datastar.js":     jsDir + "/datastar.js",
	"https://raw.githubusercontent.com/starfederation/datastar/main/bundles/datastar.js.map": jsDir + "/datastar.js.map",
	"https://github.com/saadeghi/daisyui/releases/latest/download/daisyui.mjs":               cssDir + "/daisyui.mjs",
	"https://github.com/saadeghi/daisyui/releases/latest/download/daisyui-theme.mjs":         cssDir + "/daisyui-theme.mjs",
}

func main() {
	if err := run(); err != nil {
		slog.Error("failure", "error", err)
		os.Exit(1)
	}
}

func run() error {
	dirs := []string{jsDir, cssDir}

	for _, dir := range dirs {
		if err := os.MkdirAll(dir, 0755); err != nil {
			return fmt.Errorf("create directory %s: %w", dir, err)
		}
	}

	return download(files)
}

func download(files map[string]string) error {
	var wg sync.WaitGroup
	errCh := make(chan error, len(files))

	for url, dest := range files {
		wg.Go(func() {
			base := filepath.Base(dest)
			slog.Info("downloading...", "file", base, "url", url)
			if err := downloadFile(url, dest); err != nil {
				errCh <- fmt.Errorf("download %s: %w", base, err)
			} else {
				slog.Info("finished", "file", base)
			}
		})
	}

	wg.Wait()
	close(errCh)

	var errs []error
	for err := range errCh {
		errs = append(errs, err)
	}

	return errors.Join(errs...)
}

func downloadFile(url, dest string) error {
	resp, err := http.Get(url) //nolint:gosec,noctx // static URLs, simple tool
	if err != nil {
		return fmt.Errorf("GET %s: %w", url, err)
	}
	defer resp.Body.Close() //nolint:errcheck

	if resp.StatusCode != http.StatusOK {
		return fmt.Errorf("GET %s: status %s", url, resp.Status)
	}

	out, err := os.Create(dest) //nolint:gosec // paths are hardcoded constants
	if err != nil {
		return fmt.Errorf("create %s: %w", dest, err)
	}

	if _, err := io.Copy(out, resp.Body); err != nil {
		out.Close() //nolint:errcheck
		return fmt.Errorf("write %s: %w", dest, err)
	}

	if err := out.Close(); err != nil {
		return fmt.Errorf("close %s: %w", dest, err)
	}

	return nil
}