package main

import (
	"bytes"
	"fmt"
	"io"
	"log"
	"net/http"
	"os"
	"path/filepath"
	"strings"
)

func main() {
	if len(os.Args) <= 1 || os.Args[1] == "serve" {
		serve()
		return
	}

	switch os.Args[1] {
	case "build":
		out := "dist/xjs.js"
		if len(os.Args) >= 3 && strings.TrimSpace(os.Args[2]) != "" {
			out = os.Args[2]
		}
		if err := build(out); err != nil {
			log.Fatal(err)
		}
		log.Printf("Built %s\n", out)
	default:
		fmt.Println("Usage:")
		fmt.Println("  go run main.go serve            # dev server (default)")
		fmt.Println("  go run main.go build [out.js]   # bundle animal.js + layer.js into dist/xjs.js (or out.js)")
		os.Exit(2)
	}
}

func serve() {
	// Serve files from the current directory
	fs := http.FileServer(http.Dir("."))
	http.Handle("/", fs)

	log.Println("Listening on :8080...")
	if err := http.ListenAndServe(":8080", nil); err != nil {
		log.Fatal(err)
	}
}

func readFile(path string) ([]byte, error) {
	f, err := os.Open(path)
	if err != nil {
		return nil, err
	}
	defer f.Close()
	return io.ReadAll(f)
}

func ensureDirForFile(out string) error {
	dir := filepath.Dir(out)
	if dir == "." || dir == "/" {
		return nil
	}
	return os.MkdirAll(dir, 0o755)
}

func build(out string) error {
	animal, err := readFile("animal.js")
	if err != nil {
		return fmt.Errorf("read animal.js: %w", err)
	}
	layer, err := readFile("layer.js")
	if err != nil {
		return fmt.Errorf("read layer.js: %w", err)
	}

	var buf bytes.Buffer
	buf.WriteString("// xjs.js - combined single-file build (animal + layer)\n")
	buf.WriteString("// Generated by `go run main.go build`.\n")
	buf.WriteString("// NOTE: Do not edit this file directly in development.\n")
	buf.WriteString("//       Edit animal.js / layer.js instead.\n\n")

	// Keep layer first to match previous bundled layout; runtime lookups are lazy anyway.
	buf.WriteString("/* --- layer.js --- */\n")
	buf.Write(layer)
	if !bytes.HasSuffix(layer, []byte("\n")) {
		buf.WriteByte('\n')
	}
	buf.WriteString("\n/* --- animal.js --- */\n")
	buf.Write(animal)
	if !bytes.HasSuffix(animal, []byte("\n")) {
		buf.WriteByte('\n')
	}

	// Export globals expected by docs/users.
	buf.WriteString("\n;(function(g){\n")
	buf.WriteString("  try { if (g && g.animal && !g.xjs) g.xjs = g.animal; } catch {}\n")
	buf.WriteString("  try { if (g && g.XJS_GLOBAL_DOLLAR && !g.$ && g.xjs) g.$ = g.xjs; } catch {}\n")
	buf.WriteString("})(typeof window !== 'undefined' ? window : (typeof globalThis !== 'undefined' ? globalThis : this));\n")

	if err := ensureDirForFile(out); err != nil {
		return fmt.Errorf("mkdir %s: %w", filepath.Dir(out), err)
	}
	if err := os.WriteFile(out, buf.Bytes(), 0o644); err != nil {
		return fmt.Errorf("write %s: %w", out, err)
	}
	return nil
}