// Package handlers provides HTTP handlers for the rdev API.
package handlers

import (
	"encoding/json"
	"errors"
	"fmt"
	"net/http"
	"net/url"
	"strconv"

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

// WorkHandler handles work queue endpoints.
type WorkHandler struct {
	workService *service.WorkService
}

// NewWorkHandler creates a new work handler.
func NewWorkHandler(workService *service.WorkService) *WorkHandler {
	return &WorkHandler{
		workService: workService,
	}
}

// Mount registers the work queue routes.
func (h *WorkHandler) Mount(r api.Router) {
	r.Route("/work", func(r chi.Router) {
		// Task submission
		r.Post("/enqueue", h.Enqueue)

		// Worker endpoints (for workers polling for tasks)
		r.Post("/dequeue", h.Dequeue)

		// Task management
		r.Get("/{taskId}", h.GetTask)
		r.Get("/{taskId}/status", h.GetStatus)
		r.Post("/{taskId}/complete", h.Complete)
		r.Post("/{taskId}/fail", h.Fail)
		r.Post("/{taskId}/cancel", h.Cancel)

		// Project-scoped list
		r.Get("/projects/{projectId}", h.ListByProject)

		// Queue stats
		r.Get("/stats", h.Stats)
	})
}

// EnqueueWorkRequest is the request body for POST /work/enqueue.
type EnqueueWorkRequest struct {
	ProjectID   string         `json:"project_id"`
	TaskType    string         `json:"task_type"`
	Spec        map[string]any `json:"task_spec"`
	Priority    int            `json:"priority,omitempty"`
	CallbackURL string         `json:"callback_url,omitempty"`
	MaxRetries  int            `json:"max_retries,omitempty"`
}

// EnqueueWorkResponse is the response for POST /work/enqueue.
type EnqueueWorkResponse struct {
	TaskID    string `json:"task_id"`
	StatusURL string `json:"status_url"`
}

// Enqueue adds a task to the work queue.
// POST /work/enqueue
func (h *WorkHandler) Enqueue(w http.ResponseWriter, r *http.Request) {
	var req EnqueueWorkRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		api.WriteBadRequest(w, r, "invalid request body")
		return
	}

	// Validate required fields
	if req.ProjectID == "" {
		api.WriteBadRequest(w, r, "project_id is required")
		return
	}
	if req.TaskType == "" {
		api.WriteBadRequest(w, r, "task_type is required")
		return
	}

	// Validate task type
	taskType := port.WorkTaskType(req.TaskType)
	if !taskType.IsValid() {
		api.WriteBadRequest(w, r, "task_type must be one of: build, test, deploy, custom")
		return
	}

	// Validate callback URL if provided
	if req.CallbackURL != "" {
		parsedURL, err := url.Parse(req.CallbackURL)
		if err != nil || (parsedURL.Scheme != "http" && parsedURL.Scheme != "https") {
			api.WriteBadRequest(w, r, "callback_url must be a valid HTTP/HTTPS URL")
			return
		}
	}

	result, err := h.workService.EnqueueTask(r.Context(), service.EnqueueTaskRequest{
		ProjectID:   req.ProjectID,
		Type:        taskType,
		Spec:        req.Spec,
		Priority:    req.Priority,
		CallbackURL: req.CallbackURL,
		MaxRetries:  req.MaxRetries,
	})
	if err != nil {
		api.WriteInternalError(w, r, "failed to enqueue task")
		return
	}

	api.WriteCreated(w, r, EnqueueWorkResponse{
		TaskID:    result.TaskID,
		StatusURL: result.StatusURL,
	})
}

// DequeueWorkRequest is the request body for POST /work/dequeue.
type DequeueWorkRequest struct {
	WorkerID string `json:"worker_id"`
}

// DequeueWorkResponse is the response for POST /work/dequeue.
type DequeueWorkResponse struct {
	Task *WorkTaskDTO `json:"task,omitempty"`
}

// WorkTaskDTO is the data transfer object for work tasks.
type WorkTaskDTO struct {
	ID          string         `json:"id"`
	ProjectID   string         `json:"project_id"`
	Type        string         `json:"type"`
	Spec        map[string]any `json:"spec"`
	Status      string         `json:"status"`
	Priority    int            `json:"priority"`
	WorkerID    string         `json:"worker_id,omitempty"`
	CallbackURL string         `json:"callback_url,omitempty"`
	CreatedAt   string         `json:"created_at"`
	StartedAt   string         `json:"started_at,omitempty"`
	CompletedAt string         `json:"completed_at,omitempty"`
	Result      *WorkResultDTO `json:"result,omitempty"`
	Error       string         `json:"error,omitempty"`
	RetryCount  int            `json:"retry_count"`
	MaxRetries  int            `json:"max_retries"`
}

// WorkResultDTO is the data transfer object for work results.
type WorkResultDTO struct {
	Output    string            `json:"output,omitempty"`
	Artifacts map[string]string `json:"artifacts,omitempty"`
}

// toWorkTaskDTO converts a port.WorkTask to a WorkTaskDTO.
func toWorkTaskDTO(t *port.WorkTask) *WorkTaskDTO {
	if t == nil {
		return nil
	}
	dto := &WorkTaskDTO{
		ID:          t.ID,
		ProjectID:   t.ProjectID,
		Type:        string(t.Type),
		Spec:        t.Spec,
		Status:      string(t.Status),
		Priority:    t.Priority,
		WorkerID:    t.WorkerID,
		CallbackURL: t.CallbackURL,
		CreatedAt:   t.CreatedAt.Format("2006-01-02T15:04:05Z07:00"),
		Error:       t.Error,
		RetryCount:  t.RetryCount,
		MaxRetries:  t.MaxRetries,
	}
	if t.StartedAt != nil {
		dto.StartedAt = t.StartedAt.Format("2006-01-02T15:04:05Z07:00")
	}
	if t.CompletedAt != nil {
		dto.CompletedAt = t.CompletedAt.Format("2006-01-02T15:04:05Z07:00")
	}
	if t.Result != nil {
		dto.Result = &WorkResultDTO{
			Output:    t.Result.Output,
			Artifacts: t.Result.Artifacts,
		}
	}
	return dto
}

// Dequeue claims the next available task for a worker.
// POST /work/dequeue
func (h *WorkHandler) Dequeue(w http.ResponseWriter, r *http.Request) {
	var req DequeueWorkRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		api.WriteBadRequest(w, r, "invalid request body")
		return
	}

	if req.WorkerID == "" {
		api.WriteBadRequest(w, r, "worker_id is required")
		return
	}

	task, err := h.workService.DequeueTask(r.Context(), req.WorkerID)
	if err != nil {
		api.WriteInternalError(w, r, "failed to dequeue task")
		return
	}

	api.WriteSuccess(w, r, DequeueWorkResponse{
		Task: toWorkTaskDTO(task),
	})
}

// GetTask retrieves a task by ID.
// GET /work/{taskId}
func (h *WorkHandler) GetTask(w http.ResponseWriter, r *http.Request) {
	taskID := chi.URLParam(r, "taskId")

	task, err := h.workService.GetTask(r.Context(), taskID)
	if err != nil {
		if errors.Is(err, domain.ErrWorkTaskNotFound) {
			api.WriteNotFound(w, r, fmt.Sprintf("task not found: %s", taskID))
			return
		}
		api.WriteInternalError(w, r, "failed to get task")
		return
	}

	api.WriteSuccess(w, r, toWorkTaskDTO(task))
}

// GetStatus returns the status of a task.
// GET /work/{taskId}/status
func (h *WorkHandler) GetStatus(w http.ResponseWriter, r *http.Request) {
	taskID := chi.URLParam(r, "taskId")

	task, err := h.workService.GetTask(r.Context(), taskID)
	if err != nil {
		if errors.Is(err, domain.ErrWorkTaskNotFound) {
			api.WriteNotFound(w, r, fmt.Sprintf("task not found: %s", taskID))
			return
		}
		api.WriteInternalError(w, r, "failed to get task")
		return
	}

	api.WriteSuccess(w, r, map[string]any{
		"task_id": task.ID,
		"status":  string(task.Status),
		"error":   task.Error,
	})
}

// CompleteWorkRequest is the request body for POST /work/{taskId}/complete.
type CompleteWorkRequest struct {
	Output    string            `json:"output,omitempty"`
	Artifacts map[string]string `json:"artifacts,omitempty"`
}

// Complete marks a task as successfully completed.
// POST /work/{taskId}/complete
func (h *WorkHandler) Complete(w http.ResponseWriter, r *http.Request) {
	taskID := chi.URLParam(r, "taskId")

	var req CompleteWorkRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		api.WriteBadRequest(w, r, "invalid request body")
		return
	}

	result := &port.WorkResult{
		Output:    req.Output,
		Artifacts: req.Artifacts,
	}

	if err := h.workService.CompleteTask(r.Context(), taskID, result); err != nil {
		if errors.Is(err, domain.ErrWorkTaskNotFound) {
			api.WriteNotFound(w, r, fmt.Sprintf("task not found: %s", taskID))
			return
		}
		api.WriteInternalError(w, r, "failed to complete task")
		return
	}

	api.WriteSuccess(w, r, map[string]any{
		"task_id": taskID,
		"status":  "completed",
		"message": "task completed successfully",
	})
}

// FailWorkRequest is the request body for POST /work/{taskId}/fail.
type FailWorkRequest struct {
	Error string `json:"error"`
}

// Fail marks a task as failed.
// POST /work/{taskId}/fail
func (h *WorkHandler) Fail(w http.ResponseWriter, r *http.Request) {
	taskID := chi.URLParam(r, "taskId")

	var req FailWorkRequest
	if err := json.NewDecoder(r.Body).Decode(&req); err != nil {
		api.WriteBadRequest(w, r, "invalid request body")
		return
	}

	if req.Error == "" {
		api.WriteBadRequest(w, r, "error message is required")
		return
	}

	if err := h.workService.FailTask(r.Context(), taskID, req.Error); err != nil {
		if errors.Is(err, domain.ErrWorkTaskNotFound) {
			api.WriteNotFound(w, r, fmt.Sprintf("task not found: %s", taskID))
			return
		}
		api.WriteInternalError(w, r, "failed to fail task")
		return
	}

	api.WriteSuccess(w, r, map[string]any{
		"task_id": taskID,
		"status":  "failed",
		"message": "task marked as failed",
	})
}

// Cancel cancels a pending task.
// POST /work/{taskId}/cancel
func (h *WorkHandler) Cancel(w http.ResponseWriter, r *http.Request) {
	taskID := chi.URLParam(r, "taskId")

	if err := h.workService.CancelTask(r.Context(), taskID); err != nil {
		if errors.Is(err, domain.ErrWorkTaskNotFound) {
			api.WriteNotFound(w, r, fmt.Sprintf("task not found: %s", taskID))
			return
		}
		api.WriteBadRequest(w, r, err.Error())
		return
	}

	api.WriteSuccess(w, r, map[string]any{
		"task_id": taskID,
		"status":  "cancelled",
		"message": "task cancelled successfully",
	})
}

// ListByProject returns tasks for a project with pagination.
// GET /work/projects/{projectId}?status=pending&limit=50&offset=0
func (h *WorkHandler) ListByProject(w http.ResponseWriter, r *http.Request) {
	projectID := chi.URLParam(r, "projectId")

	// Parse and validate optional status filter
	var status *port.WorkTaskStatus
	if s := r.URL.Query().Get("status"); s != "" {
		st := port.WorkTaskStatus(s)
		if !st.IsValid() {
			api.WriteBadRequest(w, r, "invalid status filter: must be pending, running, completed, failed, or cancelled")
			return
		}
		status = &st
	}

	// Parse pagination options
	opts := port.DefaultWorkListOptions()
	if limitStr := r.URL.Query().Get("limit"); limitStr != "" {
		limit, err := strconv.Atoi(limitStr)
		if err != nil {
			api.WriteBadRequest(w, r, "limit must be a valid integer")
			return
		}
		opts.Limit = limit
	}
	if offsetStr := r.URL.Query().Get("offset"); offsetStr != "" {
		offset, err := strconv.Atoi(offsetStr)
		if err != nil {
			api.WriteBadRequest(w, r, "offset must be a valid integer")
			return
		}
		opts.Offset = offset
	}

	result, err := h.workService.ListByProject(r.Context(), projectID, status, opts)
	if err != nil {
		api.WriteInternalError(w, r, "failed to list tasks")
		return
	}

	dtos := make([]*WorkTaskDTO, len(result.Tasks))
	for i, t := range result.Tasks {
		dtos[i] = toWorkTaskDTO(t)
	}

	api.WriteSuccess(w, r, map[string]any{
		"tasks":  dtos,
		"total":  result.Total,
		"limit":  result.Limit,
		"offset": result.Offset,
	})
}

// WorkStatsResponse is the response for GET /work/stats.
type WorkStatsResponse struct {
	Pending       int64  `json:"pending"`
	Running       int64  `json:"running"`
	Completed     int64  `json:"completed"`
	Failed        int64  `json:"failed"`
	Cancelled     int64  `json:"cancelled"`
	OldestPending string `json:"oldest_pending,omitempty"`
}

// Stats returns queue statistics.
// GET /work/stats
func (h *WorkHandler) Stats(w http.ResponseWriter, r *http.Request) {
	stats, err := h.workService.GetStats(r.Context())
	if err != nil {
		api.WriteInternalError(w, r, "failed to get queue stats")
		return
	}

	resp := WorkStatsResponse{
		Pending:   stats.Pending,
		Running:   stats.Running,
		Completed: stats.Completed,
		Failed:    stats.Failed,
		Cancelled: stats.Cancelled,
	}
	if stats.OldestPending != nil {
		// Convert to human-readable duration
		resp.OldestPending = formatDuration(*stats.OldestPending)
	}

	api.WriteSuccess(w, r, resp)
}

// formatDuration formats a duration in a human-readable way.
func formatDuration(d interface{ Seconds() float64 }) string {
	secs := d.Seconds()
	if secs < 60 {
		return fmt.Sprintf("%.0fs", secs)
	}
	mins := secs / 60
	if mins < 60 {
		return fmt.Sprintf("%.1fm", mins)
	}
	hours := mins / 60
	if hours < 24 {
		return fmt.Sprintf("%.1fh", hours)
	}
	days := hours / 24
	return fmt.Sprintf("%.1fd", days)
}