package handlers

import (
	"context"
	"errors"
	"fmt"
	"net/http"
	"time"

	"github.com/go-chi/chi/v5"
	"github.com/orchard9/rdev/internal/domain"
	"github.com/orchard9/rdev/internal/port"
	"github.com/orchard9/rdev/pkg/api"
)

// SessionExecRequest is the JSON body for executing a command in a session.
type SessionExecRequest struct {
	Type     string `json:"type"`                // "claude", "shell", or "git"
	Prompt   string `json:"prompt,omitempty"`     // For claude commands
	Command  string `json:"command,omitempty"`    // For shell/git commands
	Args     []string `json:"args,omitempty"`     // Additional arguments
	StreamID string `json:"stream_id,omitempty"` // Client-provided stream ID (optional)
}

// SessionExecResponse is the JSON response for a session exec command.
type SessionExecResponse struct {
	ID        string `json:"id"`
	SessionID string `json:"session_id"`
	Type      string `json:"type"`
	Status    string `json:"status"`
	StreamURL string `json:"stream_url"`
}

// Exec executes a command in the context of an active session.
// POST /projects/{id}/sessions/{sid}/exec
func (h *SessionsHandler) Exec(w http.ResponseWriter, r *http.Request) {
	projectID := chi.URLParam(r, "id")
	if err := domain.ValidateProjectID(projectID); err != nil {
		api.WriteBadRequest(w, r, "invalid project id")
		return
	}

	sid := chi.URLParam(r, "sid")
	if sid == "" {
		api.WriteBadRequest(w, r, "session id is required")
		return
	}

	var req SessionExecRequest
	if err := api.DecodeJSON(r, &req); err != nil {
		api.WriteBadRequest(w, r, "invalid request body")
		return
	}

	// Validate command type and type-specific fields.
	cmdType := domain.CommandType(req.Type)
	switch cmdType {
	case domain.CommandTypeClaude:
		if req.Prompt == "" {
			api.WriteBadRequest(w, r, "prompt is required for claude commands")
			return
		}
	case domain.CommandTypeShell:
		if req.Command == "" {
			api.WriteBadRequest(w, r, "command is required for shell commands")
			return
		}
	case domain.CommandTypeGit:
		if req.Command == "" {
			api.WriteBadRequest(w, r, "command is required for git commands")
			return
		}
	default:
		api.WriteBadRequest(w, r, "type must be claude, shell, or git")
		return
	}

	ctx, cancel := context.WithTimeout(r.Context(), TimeoutStandard)
	defer cancel()

	// Get session and verify it belongs to this project and is active.
	session, err := h.sessionService.Get(ctx, domain.SessionID(sid))
	if err != nil {
		if errors.Is(err, domain.ErrSessionNotFound) {
			api.WriteNotFound(w, r, "session not found")
			return
		}
		api.WriteInternalError(w, r, "Failed to get session")
		return
	}
	if string(session.ProjectID) != projectID {
		api.WriteNotFound(w, r, "session not found")
		return
	}
	if !session.IsActive() {
		api.WriteBadRequest(w, r, "session is not active")
		return
	}

	// Touch activity.
	_ = h.sessionService.TouchActivity(ctx, session.ID)

	// Build command args.
	var args []string
	switch cmdType {
	case domain.CommandTypeClaude:
		args = append([]string{req.Prompt}, req.Args...)
	case domain.CommandTypeShell, domain.CommandTypeGit:
		args = append([]string{req.Command}, req.Args...)
	}

	// Generate stream ID.
	streamID := req.StreamID
	if streamID == "" {
		streamID = fmt.Sprintf("session-%s-%d", sid, time.Now().UnixNano())
	}

	cmd := &domain.Command{
		ID:        domain.CommandID(streamID),
		ProjectID: domain.ProjectID(projectID),
		Type:      cmdType,
		Args:      args,
		StartedAt: time.Now(),
	}

	// Execute in background goroutine.
	go h.executeSessionCommand(r.Context(), cmd, session.PodName, streamID)

	streamURL := fmt.Sprintf("/projects/%s/sessions/%s/events?stream_id=%s", projectID, sid, streamID)

	api.WriteCreated(w, r, SessionExecResponse{
		ID:        streamID,
		SessionID: string(session.ID),
		Type:      req.Type,
		Status:    "running",
		StreamURL: streamURL,
	})
}

// executeSessionCommand runs a command and streams output to subscribers.
func (h *SessionsHandler) executeSessionCommand(parentCtx context.Context, cmd *domain.Command, podName, streamID string) {
	ctx, cancel := context.WithTimeout(context.WithoutCancel(parentCtx), TimeoutLongRunning)
	defer cancel()

	result, _ := h.executor.Execute(ctx, cmd, podName, func(line domain.OutputLine) {
		h.streams.Publish(streamID, port.StreamEvent{
			Type: "output",
			Data: map[string]any{
				"line":   line.Line,
				"stream": line.Stream,
			},
		})
	})

	// Publish completion event.
	h.streams.Publish(streamID, port.StreamEvent{
		Type: "complete",
		Data: map[string]any{
			"exit_code":   result.ExitCode,
			"duration_ms": result.DurationMs,
		},
	})

	// Allow subscribers time to receive the completion event before cleanup.
	time.Sleep(30 * time.Second)
	h.streams.Close(streamID)
}

// Events streams session command output via Server-Sent Events.
// GET /projects/{id}/sessions/{sid}/events
func (h *SessionsHandler) Events(w http.ResponseWriter, r *http.Request) {
	projectID := chi.URLParam(r, "id")
	if err := domain.ValidateProjectID(projectID); err != nil {
		api.WriteBadRequest(w, r, "invalid project id")
		return
	}

	sid := chi.URLParam(r, "sid")
	if sid == "" {
		api.WriteBadRequest(w, r, "session id is required")
		return
	}

	streamID := r.URL.Query().Get("stream_id")
	lastEventID := r.Header.Get("Last-Event-ID")

	ctx, cancel := context.WithTimeout(r.Context(), TimeoutFastLookup)
	defer cancel()

	// Verify session exists and belongs to project.
	session, err := h.sessionService.Get(ctx, domain.SessionID(sid))
	if err != nil {
		if errors.Is(err, domain.ErrSessionNotFound) {
			api.WriteNotFound(w, r, "session not found")
			return
		}
		api.WriteInternalError(w, r, "Failed to get session")
		return
	}
	if string(session.ProjectID) != projectID {
		api.WriteNotFound(w, r, "session not found")
		return
	}

	// Touch activity.
	_ = h.sessionService.TouchActivity(ctx, session.ID)

	// Set SSE headers.
	w.Header().Set("Content-Type", "text/event-stream")
	w.Header().Set("Cache-Control", "no-cache")
	w.Header().Set("Connection", "keep-alive")
	w.Header().Set("Access-Control-Allow-Origin", "*")

	flusher, ok := w.(http.Flusher)
	if !ok {
		api.WriteInternalError(w, r, "SSE not supported")
		return
	}

	// Subscribe to events with Last-Event-ID support.
	var events <-chan port.StreamEvent
	var cleanup func()
	if lastEventID != "" {
		events, cleanup = h.streams.SubscribeFromID(streamID, lastEventID)
	} else {
		events, cleanup = h.streams.Subscribe(streamID)
	}
	defer cleanup()

	// Send initial connected event.
	writeSSE(w, flusher, "connected", map[string]any{
		"session_id":   sid,
		"stream_id":    streamID,
		"reconnecting": lastEventID != "",
	})

	// Stream events until client disconnects or stream closes.
	reqCtx := r.Context()
	heartbeat := time.NewTicker(30 * time.Second)
	defer heartbeat.Stop()

	for {
		select {
		case <-reqCtx.Done():
			return
		case event, ok := <-events:
			if !ok {
				return
			}
			writeSSEWithID(w, flusher, event.ID, event.Type, event.Data)
			if event.Type == "complete" {
				return
			}
		case <-heartbeat.C:
			writeSSE(w, flusher, "heartbeat", map[string]any{
				"timestamp": time.Now().UTC().Format(time.RFC3339),
			})
		}
	}
}