package handler

import (
	"encoding/json"
	"log/slog"
	"net/http"

	"github.com/go-chi/chi/v5"
	db "github.com/multica-ai/multica/server/pkg/db/generated"
	"github.com/multica-ai/multica/server/pkg/protocol"
)

// ---------------------------------------------------------------------------
// Chat Sessions
// ---------------------------------------------------------------------------

type CreateChatSessionRequest struct {
	AgentID string `json:"agent_id"`
	Title   string `json:"title"`
}

func (h *Handler) CreateChatSession(w http.ResponseWriter, r *http.Request) {
	userID, ok := requireUserID(w, r)
	if !ok {
		return
	}
	workspaceID := ctxWorkspaceID(r.Context())

	var req CreateChatSessionRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}
	if req.AgentID == "" {
		writeError(w, http.StatusBadRequest, "agent_id is required")
		return
	}
	agentID, ok := parseUUIDOrBadRequest(w, req.AgentID, "agent_id")
	if !ok {
		return
	}
	workspaceUUID, ok := parseUUIDOrBadRequest(w, workspaceID, "workspace id")
	if !ok {
		return
	}

	// Verify agent exists in workspace.
	agent, err := h.Queries.GetAgentInWorkspace(r.Context(), db.GetAgentInWorkspaceParams{
		ID:          agentID,
		WorkspaceID: workspaceUUID,
	})
	if err != nil {
		writeError(w, http.StatusNotFound, "agent not found")
		return
	}
	if agent.ArchivedAt.Valid {
		writeError(w, http.StatusBadRequest, "agent is archived")
		return
	}

	session, err := h.Queries.CreateChatSession(r.Context(), db.CreateChatSessionParams{
		WorkspaceID: workspaceUUID,
		AgentID:     agentID,
		CreatorID:   parseUUID(userID),
		Title:       req.Title,
	})
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to create chat session")
		return
	}

	writeJSON(w, http.StatusCreated, chatSessionToResponse(session))
}

func (h *Handler) ListChatSessions(w http.ResponseWriter, r *http.Request) {
	userID, ok := requireUserID(w, r)
	if !ok {
		return
	}
	workspaceID := ctxWorkspaceID(r.Context())

	status := r.URL.Query().Get("status")

	// Two call sites → two row types with identical shape. Collect into a
	// common response slice via small per-branch loops.
	var resp []ChatSessionResponse
	if status == "all" {
		rows, err := h.Queries.ListAllChatSessionsByCreator(r.Context(), db.ListAllChatSessionsByCreatorParams{
			WorkspaceID: parseUUID(workspaceID),
			CreatorID:   parseUUID(userID),
		})
		if err != nil {
			writeError(w, http.StatusInternalServerError, "failed to list chat sessions")
			return
		}
		resp = make([]ChatSessionResponse, len(rows))
		for i, s := range rows {
			resp[i] = ChatSessionResponse{
				ID:          uuidToString(s.ID),
				WorkspaceID: uuidToString(s.WorkspaceID),
				AgentID:     uuidToString(s.AgentID),
				CreatorID:   uuidToString(s.CreatorID),
				Title:       s.Title,
				Status:      s.Status,
				HasUnread:   s.HasUnread,
				CreatedAt:   timestampToString(s.CreatedAt),
				UpdatedAt:   timestampToString(s.UpdatedAt),
			}
		}
	} else {
		rows, err := h.Queries.ListChatSessionsByCreator(r.Context(), db.ListChatSessionsByCreatorParams{
			WorkspaceID: parseUUID(workspaceID),
			CreatorID:   parseUUID(userID),
		})
		if err != nil {
			writeError(w, http.StatusInternalServerError, "failed to list chat sessions")
			return
		}
		resp = make([]ChatSessionResponse, len(rows))
		for i, s := range rows {
			resp[i] = ChatSessionResponse{
				ID:          uuidToString(s.ID),
				WorkspaceID: uuidToString(s.WorkspaceID),
				AgentID:     uuidToString(s.AgentID),
				CreatorID:   uuidToString(s.CreatorID),
				Title:       s.Title,
				Status:      s.Status,
				HasUnread:   s.HasUnread,
				CreatedAt:   timestampToString(s.CreatedAt),
				UpdatedAt:   timestampToString(s.UpdatedAt),
			}
		}
	}
	writeJSON(w, http.StatusOK, resp)
}

func (h *Handler) loadChatSessionForUser(w http.ResponseWriter, r *http.Request, userID, workspaceID, sessionID string) (db.ChatSession, bool) {
	sessionUUID, ok := parseUUIDOrBadRequest(w, sessionID, "chat session id")
	if !ok {
		return db.ChatSession{}, false
	}
	workspaceUUID, ok := parseUUIDOrBadRequest(w, workspaceID, "workspace id")
	if !ok {
		return db.ChatSession{}, false
	}
	session, err := h.Queries.GetChatSessionInWorkspace(r.Context(), db.GetChatSessionInWorkspaceParams{
		ID:          sessionUUID,
		WorkspaceID: workspaceUUID,
	})
	if err != nil {
		writeError(w, http.StatusNotFound, "chat session not found")
		return db.ChatSession{}, false
	}
	if uuidToString(session.CreatorID) != userID {
		writeError(w, http.StatusForbidden, "not your chat session")
		return db.ChatSession{}, false
	}
	return session, true
}

func (h *Handler) GetChatSession(w http.ResponseWriter, r *http.Request) {
	userID, ok := requireUserID(w, r)
	if !ok {
		return
	}
	workspaceID := ctxWorkspaceID(r.Context())
	sessionID := chi.URLParam(r, "sessionId")

	session, ok := h.loadChatSessionForUser(w, r, userID, workspaceID, sessionID)
	if !ok {
		return
	}

	writeJSON(w, http.StatusOK, chatSessionToResponse(session))
}

func (h *Handler) ArchiveChatSession(w http.ResponseWriter, r *http.Request) {
	userID, ok := requireUserID(w, r)
	if !ok {
		return
	}
	workspaceID := ctxWorkspaceID(r.Context())
	sessionID := chi.URLParam(r, "sessionId")

	session, ok := h.loadChatSessionForUser(w, r, userID, workspaceID, sessionID)
	if !ok {
		return
	}

	if err := h.Queries.ArchiveChatSession(r.Context(), session.ID); err != nil {
		writeError(w, http.StatusInternalServerError, "failed to archive chat session")
		return
	}

	w.WriteHeader(http.StatusNoContent)
}

// ---------------------------------------------------------------------------
// Chat Messages
// ---------------------------------------------------------------------------

type SendChatMessageRequest struct {
	Content string `json:"content"`
}

type SendChatMessageResponse struct {
	MessageID string `json:"message_id"`
	TaskID    string `json:"task_id"`
	// CreatedAt anchors the chat StatusPill timer the instant the user
	// hits send. Without it the front-end falls back to its local clock
	// and the timer "snaps backwards" later when WS events deliver the
	// real created_at. Returning it here means the pill renders 0s from
	// the start with a stable anchor.
	CreatedAt string `json:"created_at"`
}

func (h *Handler) SendChatMessage(w http.ResponseWriter, r *http.Request) {
	userID, ok := requireUserID(w, r)
	if !ok {
		return
	}
	workspaceID := ctxWorkspaceID(r.Context())
	sessionID := chi.URLParam(r, "sessionId")

	var req SendChatMessageRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}
	if req.Content == "" {
		writeError(w, http.StatusBadRequest, "content is required")
		return
	}

	// Load chat session.
	session, ok := h.loadChatSessionForUser(w, r, userID, workspaceID, sessionID)
	if !ok {
		return
	}
	if session.Status != "active" {
		writeError(w, http.StatusBadRequest, "chat session is archived")
		return
	}

	// Create the user message first so the daemon can always find it.
	msg, err := h.Queries.CreateChatMessage(r.Context(), db.CreateChatMessageParams{
		ChatSessionID: session.ID,
		Role:          "user",
		Content:       req.Content,
	})
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to create chat message")
		return
	}

	// Enqueue a chat task after the message exists.
	task, err := h.TaskService.EnqueueChatTask(r.Context(), session)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to enqueue chat task: "+err.Error())
		return
	}

	// Touch session updated_at.
	if err := h.Queries.TouchChatSession(r.Context(), session.ID); err != nil {
		slog.Warn("failed to touch chat session", "session_id", sessionID, "error", err)
	}

	// Broadcast the user message.
	resolvedSessionID := uuidToString(session.ID)
	h.publishChat(protocol.EventChatMessage, workspaceID, "member", userID, resolvedSessionID, protocol.ChatMessagePayload{
		ChatSessionID: resolvedSessionID,
		MessageID:     uuidToString(msg.ID),
		Role:          "user",
		Content:       req.Content,
		TaskID:        uuidToString(task.ID),
		CreatedAt:     timestampToString(msg.CreatedAt),
	})

	writeJSON(w, http.StatusCreated, SendChatMessageResponse{
		MessageID: uuidToString(msg.ID),
		TaskID:    uuidToString(task.ID),
		CreatedAt: timestampToString(task.CreatedAt),
	})
}

func (h *Handler) ListChatMessages(w http.ResponseWriter, r *http.Request) {
	userID, ok := requireUserID(w, r)
	if !ok {
		return
	}
	workspaceID := ctxWorkspaceID(r.Context())
	sessionID := chi.URLParam(r, "sessionId")

	session, ok := h.loadChatSessionForUser(w, r, userID, workspaceID, sessionID)
	if !ok {
		return
	}

	messages, err := h.Queries.ListChatMessages(r.Context(), session.ID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to list chat messages")
		return
	}

	resp := make([]ChatMessageResponse, len(messages))
	for i, m := range messages {
		resp[i] = chatMessageToResponse(m)
	}
	writeJSON(w, http.StatusOK, resp)
}

// PendingChatTaskResponse is returned by GetPendingChatTask — either the
// current in-flight task's id/status, or an empty object when none is active.
// CreatedAt is the anchor the frontend uses to time the chat StatusPill
// (elapsed seconds = now - CreatedAt). It must come from the server because
// optimistic seeds don't have a real task created_at and the timer needs to
// survive refresh / reopen.
type PendingChatTaskResponse struct {
	TaskID    string `json:"task_id,omitempty"`
	Status    string `json:"status,omitempty"`
	CreatedAt string `json:"created_at,omitempty"`
}

// MarkChatSessionRead clears the session's unread_since (→ has_unread=false)
// and broadcasts chat:session_read so other devices of the same user drop
// their badges.
func (h *Handler) MarkChatSessionRead(w http.ResponseWriter, r *http.Request) {
	userID, ok := requireUserID(w, r)
	if !ok {
		return
	}
	workspaceID := ctxWorkspaceID(r.Context())
	sessionID := chi.URLParam(r, "sessionId")

	session, ok := h.loadChatSessionForUser(w, r, userID, workspaceID, sessionID)
	if !ok {
		return
	}

	if err := h.Queries.MarkChatSessionRead(r.Context(), session.ID); err != nil {
		writeError(w, http.StatusInternalServerError, "failed to mark session read")
		return
	}

	resolvedSessionID := uuidToString(session.ID)
	h.publishChat(protocol.EventChatSessionRead, workspaceID, "member", userID, resolvedSessionID, protocol.ChatSessionReadPayload{
		ChatSessionID: resolvedSessionID,
	})

	w.WriteHeader(http.StatusNoContent)
}

// PendingChatTasksResponse is the aggregate view consumed by the FAB.
type PendingChatTasksResponse struct {
	Tasks []PendingChatTaskItem `json:"tasks"`
}

type PendingChatTaskItem struct {
	TaskID        string `json:"task_id"`
	Status        string `json:"status"`
	ChatSessionID string `json:"chat_session_id"`
}

// ListPendingChatTasks returns every in-flight chat task owned by the current
// user in this workspace. Drives the FAB's "running" indicator when the chat
// window is closed (no per-session query is subscribed).
func (h *Handler) ListPendingChatTasks(w http.ResponseWriter, r *http.Request) {
	userID, ok := requireUserID(w, r)
	if !ok {
		return
	}
	workspaceID := ctxWorkspaceID(r.Context())

	rows, err := h.Queries.ListPendingChatTasksByCreator(r.Context(), db.ListPendingChatTasksByCreatorParams{
		WorkspaceID: parseUUID(workspaceID),
		CreatorID:   parseUUID(userID),
	})
	if err != nil {
		writeError(w, http.StatusInternalServerError, "failed to list pending chat tasks")
		return
	}

	items := make([]PendingChatTaskItem, len(rows))
	for i, row := range rows {
		items[i] = PendingChatTaskItem{
			TaskID:        uuidToString(row.TaskID),
			Status:        row.Status,
			ChatSessionID: uuidToString(row.ChatSessionID),
		}
	}
	writeJSON(w, http.StatusOK, PendingChatTasksResponse{Tasks: items})
}

// GetPendingChatTask returns the most recent in-flight task (queued / dispatched
// / running) for a chat session. The frontend polls this on mount / session
// switch so pending UI state survives refresh and reopen.
func (h *Handler) GetPendingChatTask(w http.ResponseWriter, r *http.Request) {
	userID, ok := requireUserID(w, r)
	if !ok {
		return
	}
	workspaceID := ctxWorkspaceID(r.Context())
	sessionID := chi.URLParam(r, "sessionId")

	session, ok := h.loadChatSessionForUser(w, r, userID, workspaceID, sessionID)
	if !ok {
		return
	}

	task, err := h.Queries.GetPendingChatTask(r.Context(), session.ID)
	if err != nil {
		// No in-flight task — return an empty object, not an error.
		writeJSON(w, http.StatusOK, PendingChatTaskResponse{})
		return
	}

	writeJSON(w, http.StatusOK, PendingChatTaskResponse{
		TaskID:    uuidToString(task.ID),
		Status:    task.Status,
		CreatedAt: timestampToString(task.CreatedAt),
	})
}

// ---------------------------------------------------------------------------
// Task cancellation (user-facing, with ownership check)
// ---------------------------------------------------------------------------

// CancelTaskByUser cancels a task after verifying the requesting user owns
// the associated chat session or issue within the current workspace.
func (h *Handler) CancelTaskByUser(w http.ResponseWriter, r *http.Request) {
	userID, ok := requireUserID(w, r)
	if !ok {
		return
	}
	workspaceID := ctxWorkspaceID(r.Context())
	taskID := chi.URLParam(r, "taskId")
	taskUUID, ok := parseUUIDOrBadRequest(w, taskID, "task id")
	if !ok {
		return
	}

	task, err := h.Queries.GetAgentTask(r.Context(), taskUUID)
	if err != nil {
		writeError(w, http.StatusNotFound, "task not found")
		return
	}

	// Verify ownership: for chat tasks, check workspace + creator;
	// for issue tasks, verify the issue belongs to the current workspace.
	if task.ChatSessionID.Valid {
		cs, err := h.Queries.GetChatSessionInWorkspace(r.Context(), db.GetChatSessionInWorkspaceParams{
			ID:          task.ChatSessionID,
			WorkspaceID: parseUUID(workspaceID),
		})
		if err != nil {
			writeError(w, http.StatusNotFound, "task not found")
			return
		}
		if uuidToString(cs.CreatorID) != userID {
			writeError(w, http.StatusForbidden, "not your task")
			return
		}
	} else if task.IssueID.Valid {
		issue, err := h.Queries.GetIssue(r.Context(), task.IssueID)
		if err != nil || uuidToString(issue.WorkspaceID) != workspaceID {
			writeError(w, http.StatusNotFound, "task not found")
			return
		}
	} else {
		writeError(w, http.StatusNotFound, "task not found")
		return
	}

	cancelled, err := h.TaskService.CancelTask(r.Context(), taskUUID)
	if err != nil {
		writeError(w, http.StatusBadRequest, err.Error())
		return
	}

	writeJSON(w, http.StatusOK, taskToResponse(*cancelled))
}

// ---------------------------------------------------------------------------
// Response types & helpers
// ---------------------------------------------------------------------------

type ChatSessionResponse struct {
	ID          string `json:"id"`
	WorkspaceID string `json:"workspace_id"`
	AgentID     string `json:"agent_id"`
	CreatorID   string `json:"creator_id"`
	Title       string `json:"title"`
	Status      string `json:"status"`
	// Only populated by list endpoints — single-session fetches return false.
	HasUnread bool   `json:"has_unread"`
	CreatedAt string `json:"created_at"`
	UpdatedAt string `json:"updated_at"`
}

type ChatMessageResponse struct {
	ID            string  `json:"id"`
	ChatSessionID string  `json:"chat_session_id"`
	Role          string  `json:"role"`
	Content       string  `json:"content"`
	TaskID        *string `json:"task_id"`
	CreatedAt     string  `json:"created_at"`
	// FailureReason flags an assistant row synthesized by FailTask's chat
	// fallback. Front-end uses it to switch to the destructive bubble.
	FailureReason *string `json:"failure_reason"`
	// ElapsedMs is the wall-clock duration from task creation to terminal
	// state. Drives "Replied in 38s" / "Failed after 12s" captions.
	ElapsedMs *int64 `json:"elapsed_ms"`
}

func chatSessionToResponse(s db.ChatSession) ChatSessionResponse {
	return ChatSessionResponse{
		ID:          uuidToString(s.ID),
		WorkspaceID: uuidToString(s.WorkspaceID),
		AgentID:     uuidToString(s.AgentID),
		CreatorID:   uuidToString(s.CreatorID),
		Title:       s.Title,
		Status:      s.Status,
		CreatedAt:   timestampToString(s.CreatedAt),
		UpdatedAt:   timestampToString(s.UpdatedAt),
	}
}

func chatMessageToResponse(m db.ChatMessage) ChatMessageResponse {
	return ChatMessageResponse{
		ID:            uuidToString(m.ID),
		ChatSessionID: uuidToString(m.ChatSessionID),
		Role:          m.Role,
		Content:       m.Content,
		TaskID:        uuidToPtr(m.TaskID),
		CreatedAt:     timestampToString(m.CreatedAt),
		FailureReason: textToPtr(m.FailureReason),
		ElapsedMs:     int8ToPtr(m.ElapsedMs),
	}
}