// Package httpapi 提供 HTTP 接口与静态资源托管。
package httpapi

import (
	"encoding/json"
	"io/fs"
	"log/slog"
	"net/http"
	"strings"
	"time"

	"git.yeij.top/AskaEth/Scoreboard/server/internal/webui"
)

// Options 是构建路由所需的依赖。
type Options struct {
	Logger  *slog.Logger
	Version string
}

// New 组装并返回服务端的 HTTP 处理器。
func New(opts Options) http.Handler {
	logger := opts.Logger
	if logger == nil {
		logger = slog.Default()
	}

	mux := http.NewServeMux()

	mux.HandleFunc("GET /api/health", func(w http.ResponseWriter, r *http.Request) {
		writeJSON(w, http.StatusOK, map[string]any{
			"ok":      true,
			"version": opts.Version,
		})
	})

	assets, err := webui.FS()
	if err != nil {
		logger.Error("前端资源不可用", "err", err)
		mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
			http.Error(w, "前端资源不可用", http.StatusServiceUnavailable)
		})
	} else {
		mux.Handle("/", staticHandler(assets))
	}

	return withRequestLog(mux, logger)
}

// staticHandler 把 URL 映射到多页面前端产物。
//
//	/            → index.html
//	/display     → display.html
//	/admin       → admin.html
//	/其他         → 按文件路径查找
func staticHandler(assets fs.FS) http.Handler {
	files := http.FileServerFS(assets)

	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		p := strings.TrimPrefix(r.URL.Path, "/")

		switch p {
		case "", "index.html":
			http.ServeFileFS(w, r, assets, "index.html")
		case "display", "display/":
			http.ServeFileFS(w, r, assets, "display.html")
		case "admin", "admin/":
			http.ServeFileFS(w, r, assets, "admin.html")
		default:
			if _, err := fs.Stat(assets, p); err != nil {
				http.NotFound(w, r)
				return
			}
			files.ServeHTTP(w, r)
		}
	})
}

func writeJSON(w http.ResponseWriter, code int, v any) {
	w.Header().Set("Content-Type", "application/json; charset=utf-8")
	w.WriteHeader(code)
	_ = json.NewEncoder(w).Encode(v)
}

type statusRecorder struct {
	http.ResponseWriter
	status int
}

func (r *statusRecorder) WriteHeader(code int) {
	r.status = code
	r.ResponseWriter.WriteHeader(code)
}

func withRequestLog(next http.Handler, logger *slog.Logger) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		start := time.Now()
		rec := &statusRecorder{ResponseWriter: w, status: http.StatusOK}
		next.ServeHTTP(rec, r)
		logger.Debug("http",
			"method", r.Method,
			"path", r.URL.Path,
			"status", rec.status,
			"dur", time.Since(start),
		)
	})
}