package gateway

import (
	"errors"
	"net/http"
	"strconv"

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

// historySessionSummary is the wire shape of one persistent session (main or sub) in the
// GET /api/v1/sessions response.
type historySessionSummary struct {
	ID        string `json:"id"`
	Type      string `json:"type"` // "main" | "sub"
	Title     string `json:"title,omitempty"`
	CreatedAt int64  `json:"createdAt"`
}

// historyMessage is the wire shape of one persisted chat message in the
// GET /api/v1/sessions/{id}/messages response. Mode is carried so the frontend renders
// the bubble without guessing (design/16 §5.1); thinking is stored and returned to the
// owner/admin (the messages route is owner/admin-only, so it never reaches a viewer).
type historyMessage struct {
	ID        string `json:"id"`
	SessionID string `json:"sessionId"`
	Role      string `json:"role"`
	Content   string `json:"content"`
	Mode      string `json:"mode,omitempty"`
	Mood      string `json:"mood,omitempty"`
	Image     string `json:"image,omitempty"`
	Thinking  string `json:"thinking,omitempty"`
	Platform  string `json:"platform,omitempty"`
	DeviceID  string `json:"deviceId,omitempty"`
	CreatedAt int64  `json:"createdAt"`
}

// handleHistorySessions returns the main session first, then every sub session (oldest
// first). It is the chat-history session list for the frontend (design/16 §2.2).
func (s *Server) handleHistorySessions(w http.ResponseWriter, r *http.Request) {
	meta, err := s.history.ListSessions(r.Context())
	if err != nil {
		s.log.Error("history list sessions", "err", err)
		writeError(w, apperr.Wrap(apperr.ErrInternal, "sessions_failed", "failed to list sessions"))
		return
	}
	out := make([]historySessionSummary, 0, len(meta))
	for _, m := range meta {
		out = append(out, historySessionSummary{
			ID:        m.ID,
			Type:      m.Type,
			Title:     m.Title,
			CreatedAt: m.CreatedAt,
		})
	}
	writeJSON(w, http.StatusOK, out)
}

// handleCreateSubSession creates a new sub session and returns its sessionId. It is a
// user-side write, so it is owner/admin-gated like /api/v1/chat.
func (s *Server) handleCreateSubSession(w http.ResponseWriter, r *http.Request) {
	if s.history == nil {
		writeError(w, &apperr.AppError{Code: "not_implemented", Message: "会话历史服务未配置（未注入 HistoryStore）", HTTPCode: http.StatusNotImplemented})
		return
	}
	ownerID := ""
	if claims, ok := auth.ClaimsFromContext(r.Context()); ok {
		ownerID = claims.Sub
	}
	id, err := s.history.NewSubSession(r.Context(), ownerID)
	if err != nil {
		s.log.Error("history create sub session", "err", err)
		writeError(w, apperr.Wrap(apperr.ErrInternal, "session_failed", "failed to create session"))
		return
	}
	writeJSON(w, http.StatusCreated, map[string]any{"sessionId": id})
}

// handleListMessages returns a page of messages for a session, newest first, with cursor
// pagination. It is the hot-paging history endpoint (design/16 §2.2, §5.1): limit defaults
// to 50 (clamped to 200), before is the oldest message's created_at from the previous page.
func (s *Server) handleListMessages(w http.ResponseWriter, r *http.Request) {
	if s.history == nil {
		writeError(w, &apperr.AppError{Code: "not_implemented", Message: "会话历史服务未配置（未注入 HistoryStore）", HTTPCode: http.StatusNotImplemented})
		return
	}
	id := r.PathValue("id")
	if id == "" {
		writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "session id is required"))
		return
	}
	limitStr := r.URL.Query().Get("limit")
	limit := historyDefaultLimit
	if limitStr != "" {
		v, err := strconv.Atoi(limitStr)
		if err != nil || v < 1 {
			writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "invalid limit"))
			return
		}
		limit = v
	}
	var before int64
	if b := r.URL.Query().Get("before"); b != "" {
		v, err := strconv.ParseInt(b, 10, 64)
		if err != nil {
			writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "invalid before"))
			return
		}
		before = v
	}
	platform := r.URL.Query().Get("platform")

	msgs, err := s.history.List(r.Context(), id, before, limit, platform)
	if err != nil {
		s.log.Error("history list messages", "err", err, "session", id)
		writeError(w, apperr.Wrap(apperr.ErrInternal, "messages_failed", "failed to list messages"))
		return
	}
	out := make([]historyMessage, 0, len(msgs))
	for _, m := range msgs {
		out = append(out, toHistoryMessage(m))
	}
	writeJSON(w, http.StatusOK, out)
}

// handleDeleteSession deletes a sub session and all its messages. The main session is
// immutable (design/16 §6) and returns 403.
func (s *Server) handleDeleteSession(w http.ResponseWriter, r *http.Request) {
	if s.history == nil {
		writeError(w, &apperr.AppError{Code: "not_implemented", Message: "会话历史服务未配置（未注入 HistoryStore）", HTTPCode: http.StatusNotImplemented})
		return
	}
	id := r.PathValue("id")
	if id == "" {
		writeError(w, apperr.Wrap(apperr.ErrBadRequest, "bad_request", "session id is required"))
		return
	}
	if err := s.history.DeleteSession(r.Context(), id); err != nil {
		if errors.Is(err, history.ErrImmutableMain) {
			writeError(w, apperr.Wrap(apperr.ErrForbidden, "forbidden", "the main session cannot be deleted"))
			return
		}
		s.log.Error("history delete session", "err", err, "session", id)
		writeError(w, apperr.Wrap(apperr.ErrInternal, "session_failed", "failed to delete session"))
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{"deleted": id})
}

// toHistoryMessage maps a stored history.Message to its wire shape.
func toHistoryMessage(m history.Message) historyMessage {
	return historyMessage{
		ID:        m.ID,
		SessionID: m.SessionID,
		Role:      m.Role,
		Content:   m.Content,
		Mode:      m.Mode,
		Mood:      m.Mood,
		Image:     m.Image,
		Thinking:  m.Thinking,
		Platform:  m.Platform,
		DeviceID:  m.DeviceID,
		CreatedAt: m.CreatedAt,
	}
}

// historyDefaultLimit is the page size used when the client omits the limit query param.
const historyDefaultLimit = 50