package gateway

import (
	"bufio"
	"fmt"
	"net"
	"net/http"
	"time"

	apperr "git.yeij.top/AskaEth/Cyrene_v2/internal/errors"
)

// cors 为已配置允许列表中的来源设置 Access-Control-* 头，并
// 短路 OPTIONS 预检请求。空来源（同源或
// 非浏览器客户端）原样放行。
func (s *Server) cors(next http.Handler) http.Handler {
	allowed, allowAll := s.allowedOrigins()
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if origin := r.Header.Get("Origin"); origin != "" && (allowAll || allowed[origin]) {
			if allowAll {
				w.Header().Set("Access-Control-Allow-Origin", "*")
			} else {
				w.Header().Set("Access-Control-Allow-Origin", origin)
			}
			w.Header().Set("Vary", "Origin")
			w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
			w.Header().Set("Access-Control-Allow-Headers", "Authorization, Content-Type, X-API-Version")
			w.Header().Set("Access-Control-Expose-Headers", voiceProviderHeader)
			w.Header().Set("Access-Control-Max-Age", "600")
		}
		if r.Method == http.MethodOptions {
			w.WriteHeader(http.StatusNoContent)
			return
		}
		next.ServeHTTP(w, r)
	})
}

// allowedOrigins 把已配置的来源列表解析成查找集合，外加针对
// "*" 通配符的允许全部标志。
func (s *Server) allowedOrigins() (map[string]bool, bool) {
	list := s.cfg.AllowedOrigins
	if len(list) == 0 {
		return map[string]bool{}, false
	}
	allowAll := false
	out := make(map[string]bool, len(list))
	for _, o := range list {
		if o == "*" {
			allowAll = true
			continue
		}
		out[o] = true
	}
	return out, allowAll
}

// recover 把下游 handler 中的 panic 转成 500 {error:...}
// 响应，而不是让进程崩溃，并记录该 panic。
func (s *Server) recover(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		defer func() {
			if rec := recover(); rec != nil {
				s.log.Error("panic recovered", "panic", rec, "method", r.Method, "path", r.URL.Path)
				writeError(w, apperr.ErrInternal)
			}
		}()
		next.ServeHTTP(w, r)
	})
}

// logging 为每个请求记录一行结构化日志（method、path、status、dur）。
func (s *Server) logging(next http.Handler) 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)
		durMs := time.Since(start).Milliseconds()
		s.recordMetric(r.Method, r.URL.Path, rec.status, durMs)
		s.log.Info("request",
			"method", r.Method,
			"path", r.URL.Path,
			"status", rec.status,
			"duration_ms", durMs,
		)
	})
}

// statusRecorder 捕获写入的状态，使 logging 中间件能报告
// 它。它转发可选的 Hijacker/Flusher 接口，因此 WebSocket
// 升级器（要求 http.Hijacker）与流式 handler 仍能工作。
type statusRecorder struct {
	http.ResponseWriter
	status int
}

// WriteHeader 在委托之前记录状态。
func (r *statusRecorder) WriteHeader(code int) {
	r.status = code
	r.ResponseWriter.WriteHeader(code)
}

// Hijack 在底层 writer 支持连接劫持时转发给它。
func (r *statusRecorder) Hijack() (net.Conn, *bufio.ReadWriter, error) {
	if hj, ok := r.ResponseWriter.(http.Hijacker); ok {
		return hj.Hijack()
	}
	return nil, nil, fmt.Errorf("gateway: hijack unsupported by %T", r.ResponseWriter)
}

// Flush 在底层 writer 支持 flush 时转发给它。
func (r *statusRecorder) Flush() {
	if f, ok := r.ResponseWriter.(http.Flusher); ok {
		f.Flush()
	}
}