package api

import (
	"context"
	"encoding/json"
	"fmt"
	"log/slog"
	"net/http"
	"time"

	"github.com/thepeterstone/claudomator/internal/executor"
	"github.com/thepeterstone/claudomator/internal/storage"
	"github.com/thepeterstone/claudomator/internal/task"
	webui "github.com/thepeterstone/claudomator/web"
	"github.com/google/uuid"
)

// Server provides the REST API and WebSocket endpoint for Claudomator.
type Server struct {
	store            *storage.DB
	logStore         logStore // injectable for tests; defaults to store
	pool             *executor.Pool
	hub              *Hub
	logger           *slog.Logger
	mux              *http.ServeMux
	claudeBinPath    string // path to claude binary; defaults to "claude"
	elaborateCmdPath string // overrides claudeBinPath; used in tests
}

func NewServer(store *storage.DB, pool *executor.Pool, logger *slog.Logger, claudeBinPath string) *Server {
	s := &Server{
		store:         store,
		logStore:      store,
		pool:          pool,
		hub:           NewHub(),
		logger:        logger,
		mux:           http.NewServeMux(),
		claudeBinPath: claudeBinPath,
	}
	s.routes()
	return s
}

func (s *Server) Handler() http.Handler {
	return corsMiddleware(s.mux)
}

func (s *Server) StartHub() {
	go s.hub.Run()
	go s.forwardResults()
}

func (s *Server) routes() {
	s.mux.HandleFunc("POST /api/tasks/elaborate", s.handleElaborateTask)
	s.mux.HandleFunc("POST /api/tasks", s.handleCreateTask)
	s.mux.HandleFunc("GET /api/tasks", s.handleListTasks)
	s.mux.HandleFunc("GET /api/tasks/{id}", s.handleGetTask)
	s.mux.HandleFunc("POST /api/tasks/{id}/run", s.handleRunTask)
	s.mux.HandleFunc("GET /api/tasks/{id}/subtasks", s.handleListSubtasks)
	s.mux.HandleFunc("GET /api/tasks/{id}/executions", s.handleListExecutions)
	s.mux.HandleFunc("GET /api/executions/{id}", s.handleGetExecution)
	s.mux.HandleFunc("GET /api/executions/{id}/logs/stream", s.handleStreamLogs)
	s.mux.HandleFunc("GET /api/templates", s.handleListTemplates)
	s.mux.HandleFunc("POST /api/templates", s.handleCreateTemplate)
	s.mux.HandleFunc("GET /api/templates/{id}", s.handleGetTemplate)
	s.mux.HandleFunc("PUT /api/templates/{id}", s.handleUpdateTemplate)
	s.mux.HandleFunc("DELETE /api/templates/{id}", s.handleDeleteTemplate)
	s.mux.HandleFunc("GET /api/ws", s.handleWebSocket)
	s.mux.HandleFunc("GET /api/health", s.handleHealth)
	s.mux.Handle("GET /", http.FileServerFS(webui.Files))
}

// forwardResults listens on the executor pool's result channel and broadcasts via WebSocket.
func (s *Server) forwardResults() {
	for result := range s.pool.Results() {
		event := map[string]interface{}{
			"type":      "task_completed",
			"task_id":   result.TaskID,
			"status":    result.Execution.Status,
			"exit_code": result.Execution.ExitCode,
			"cost_usd":  result.Execution.CostUSD,
			"error":     result.Execution.ErrorMsg,
			"timestamp": time.Now().UTC(),
		}
		data, _ := json.Marshal(event)
		s.hub.Broadcast(data)
	}
}

func (s *Server) handleHealth(w http.ResponseWriter, r *http.Request) {
	writeJSON(w, http.StatusOK, map[string]string{"status": "ok"})
}

func (s *Server) handleCreateTask(w http.ResponseWriter, r *http.Request) {
	var input struct {
		Name         string            `json:"name"`
		Description  string            `json:"description"`
		Claude       task.ClaudeConfig `json:"claude"`
		Timeout      string            `json:"timeout"`
		Priority     string            `json:"priority"`
		Tags         []string          `json:"tags"`
		ParentTaskID string            `json:"parent_task_id"`
	}
	if err := json.NewDecoder(r.Body).Decode(&input); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid JSON: " + err.Error()})
		return
	}

	now := time.Now().UTC()
	t := &task.Task{
		ID:           uuid.New().String(),
		Name:         input.Name,
		Description:  input.Description,
		Claude:       input.Claude,
		Priority:     task.Priority(input.Priority),
		Tags:         input.Tags,
		DependsOn:    []string{},
		Retry:        task.RetryConfig{MaxAttempts: 1, Backoff: "exponential"},
		State:        task.StatePending,
		CreatedAt:    now,
		UpdatedAt:    now,
		ParentTaskID: input.ParentTaskID,
	}
	if t.Priority == "" {
		t.Priority = task.PriorityNormal
	}
	if t.Tags == nil {
		t.Tags = []string{}
	}
	if input.Timeout != "" {
		dur, err := time.ParseDuration(input.Timeout)
		if err != nil {
			writeJSON(w, http.StatusBadRequest, map[string]string{"error": "invalid timeout: " + err.Error()})
			return
		}
		t.Timeout.Duration = dur
	}

	if err := task.Validate(t); err != nil {
		writeJSON(w, http.StatusBadRequest, map[string]string{"error": err.Error()})
		return
	}
	if err := s.store.CreateTask(t); err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
		return
	}

	writeJSON(w, http.StatusCreated, t)
}

func (s *Server) handleListTasks(w http.ResponseWriter, r *http.Request) {
	filter := storage.TaskFilter{}
	if state := r.URL.Query().Get("state"); state != "" {
		filter.State = task.State(state)
	}
	tasks, err := s.store.ListTasks(filter)
	if err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
		return
	}
	if tasks == nil {
		tasks = []*task.Task{}
	}
	writeJSON(w, http.StatusOK, tasks)
}

func (s *Server) handleGetTask(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	t, err := s.store.GetTask(id)
	if err != nil {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "task not found"})
		return
	}
	writeJSON(w, http.StatusOK, t)
}

func (s *Server) handleRunTask(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	t, err := s.store.GetTask(id)
	if err != nil {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "task not found"})
		return
	}

	if !task.ValidTransition(t.State, task.StateQueued) {
		writeJSON(w, http.StatusConflict, map[string]string{
			"error": fmt.Sprintf("task cannot be queued from state %s", t.State),
		})
		return
	}

	if err := s.store.UpdateTaskState(id, task.StateQueued); err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
		return
	}
	t.State = task.StateQueued

	if err := s.pool.Submit(context.Background(), t); err != nil {
		writeJSON(w, http.StatusServiceUnavailable, map[string]string{"error": fmt.Sprintf("executor pool: %v", err)})
		return
	}

	writeJSON(w, http.StatusAccepted, map[string]string{
		"message": "task queued for execution",
		"task_id": id,
	})
}

func (s *Server) handleListSubtasks(w http.ResponseWriter, r *http.Request) {
	parentID := r.PathValue("id")
	tasks, err := s.store.ListSubtasks(parentID)
	if err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
		return
	}
	if tasks == nil {
		tasks = []*task.Task{}
	}
	writeJSON(w, http.StatusOK, tasks)
}

func (s *Server) handleListExecutions(w http.ResponseWriter, r *http.Request) {
	taskID := r.PathValue("id")
	execs, err := s.store.ListExecutions(taskID)
	if err != nil {
		writeJSON(w, http.StatusInternalServerError, map[string]string{"error": err.Error()})
		return
	}
	if execs == nil {
		execs = []*storage.Execution{}
	}
	writeJSON(w, http.StatusOK, execs)
}

func (s *Server) handleGetExecution(w http.ResponseWriter, r *http.Request) {
	id := r.PathValue("id")
	exec, err := s.store.GetExecution(id)
	if err != nil {
		writeJSON(w, http.StatusNotFound, map[string]string{"error": "execution not found"})
		return
	}
	writeJSON(w, http.StatusOK, exec)
}

func writeJSON(w http.ResponseWriter, status int, v interface{}) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	json.NewEncoder(w).Encode(v)
}

func corsMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.Header().Set("Access-Control-Allow-Origin", "*")
		w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
		w.Header().Set("Access-Control-Allow-Headers", "Content-Type, Authorization")
		if r.Method == "OPTIONS" {
			w.WriteHeader(http.StatusOK)
			return
		}
		next.ServeHTTP(w, r)
	})
}