package server

import (
	"context"
	"encoding/json"
	"net/http"
	"strings"

	"chat-agent-system/internal/errcode"
	"chat-agent-system/internal/httpx"
)

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

func writeSafeError(w http.ResponseWriter, r *http.Request, status int, legacy string) {
	emitError(w, r, status, errcode.FromLegacy(status, legacy), legacy)
}

func writeDomainError(w http.ResponseWriter, r *http.Request, status int, err error) {
	if err == nil {
		writeSafeError(w, r, status, "")
		return
	}
	if st, ok := domainHTTPStatus(err); ok {
		def := errcode.FromStatus(st)
		if d, found := errcode.FromError(err); found {
			def = d
		}
		emitError(w, r, st, def, err.Error())
		return
	}
	if def, found := errcode.FromError(err); found {
		// 处理器传入的状态是既有 HTTP 契约。注册表状态只在调用方未给出时使用。
		st := status
		if st == 0 {
			st = def.Status
		}
		if st == 0 {
			st = http.StatusInternalServerError
		}
		emitError(w, r, st, def, err.Error())
		return
	}
	emitError(w, r, status, errcode.FromLegacy(status, err.Error()), err.Error())
}

func emitError(w http.ResponseWriter, r *http.Request, status int, def errcode.Def, legacy string) {
	if def.ID == "" {
		def = errcode.FromStatus(status)
	}
	details := map[string]any{}
	if def.Guide != "" {
		details["guide"] = def.Guide
	}
	if def.Module != "" {
		details["module"] = def.Module
	}
	rid := incomingRequestID(w, r)
	httpx.WriteHTTP(w, r, status, def.ID, legacy, rid, def.Message, details)
	if rid == "" && w != nil {
		rid = w.Header().Get(httpx.HeaderRequestID)
	}
	reportHTTPError(r, status, def, rid, legacy)
}

func incomingRequestID(w http.ResponseWriter, r *http.Request) string {
	if r != nil {
		if v := strings.TrimSpace(r.Header.Get(httpx.HeaderRequestID)); v != "" {
			return v
		}
	}
	if w != nil {
		if v := strings.TrimSpace(w.Header().Get(httpx.HeaderRequestID)); v != "" {
			return v
		}
	}
	return ""
}

func reportHTTPError(r *http.Request, status int, def errcode.Def, requestID, legacy string) {
	ev := errcode.Event{
		Code:        def.ID,
		Class:       def.Class,
		HTTPStatus:  status,
		RequestID:   requestID,
		Module:      def.Module,
		Source:      "http",
		Retryable:   def.Retryable,
		UserMessage: def.Message,
		Upstream:    legacy,
	}
	ctx := context.Background()
	if r != nil {
		ev.Method = r.Method
		ev.Path = r.URL.Path
		if sid := strings.TrimSpace(r.URL.Query().Get("session_id")); sid != "" {
			ev.SessionID = sid
		}
		if user := principalFromContext(r.Context()); user != nil {
			ev.ActorUserID = user.ID
		}
		ctx = r.Context()
	}
	errcode.Report(ctx, ev)
}