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

import (
	"errors"
	"net/http"

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

// WorkersHandler handles worker pool management endpoints.
type WorkersHandler struct {
	workerService *service.WorkerService
}

// NewWorkersHandler creates a new workers handler.
func NewWorkersHandler(workerService *service.WorkerService) *WorkersHandler {
	return &WorkersHandler{
		workerService: workerService,
	}
}

// Mount registers the worker pool routes.
func (h *WorkersHandler) Mount(r api.Router) {
	r.Route("/workers", func(r chi.Router) {
		// Read operations
		r.With(auth.RequireScope(auth.ScopeWorkersRead, auth.ScopeAdmin)).Get("/", h.List)
		r.With(auth.RequireScope(auth.ScopeWorkersRead, auth.ScopeAdmin)).Get("/{workerId}", h.Get)

		// Write operations
		r.With(auth.RequireScope(auth.ScopeWorkersWrite, auth.ScopeAdmin)).Post("/register", h.Register)
		r.With(auth.RequireScope(auth.ScopeWorkersWrite, auth.ScopeAdmin)).Post("/{workerId}/heartbeat", h.Heartbeat)
		r.With(auth.RequireScope(auth.ScopeWorkersWrite, auth.ScopeAdmin)).Post("/{workerId}/drain", h.Drain)
	})
}

// WorkerDTO is the data transfer object for workers.
type WorkerDTO struct {
	ID            string   `json:"id"`
	Hostname      string   `json:"hostname"`
	Status        string   `json:"status"`
	CurrentTask   string   `json:"current_task,omitempty"`
	Capabilities  []string `json:"capabilities,omitempty"`
	RegisteredAt  string   `json:"registered_at"`
	LastHeartbeat string   `json:"last_heartbeat"`
	Version       string   `json:"version,omitempty"`
}

func toWorkerDTO(w *domain.Worker) *WorkerDTO {
	if w == nil {
		return nil
	}
	return &WorkerDTO{
		ID:            w.ID,
		Hostname:      w.Hostname,
		Status:        string(w.Status),
		CurrentTask:   w.CurrentTask,
		Capabilities:  w.Capabilities,
		RegisteredAt:  w.RegisteredAt.Format("2006-01-02T15:04:05Z07:00"),
		LastHeartbeat: w.LastHeartbeat.Format("2006-01-02T15:04:05Z07:00"),
		Version:       w.Version,
	}
}

// List returns all workers with optional status filter.
// GET /workers?status=idle
func (h *WorkersHandler) List(w http.ResponseWriter, r *http.Request) {
	filter := port.WorkerFilter{}

	if s := r.URL.Query().Get("status"); s != "" {
		st := domain.WorkerStatus(s)
		if !st.IsValid() {
			api.WriteBadRequest(w, r, "invalid status: must be idle, busy, draining, or offline")
			return
		}
		filter.Status = &st
	}

	workers, err := h.workerService.ListWorkers(r.Context(), filter)
	if err != nil {
		api.WriteInternalError(w, r, "failed to list workers")
		return
	}

	dtos := make([]*WorkerDTO, len(workers))
	for i, wkr := range workers {
		dtos[i] = toWorkerDTO(wkr)
	}

	// Compute summary counts
	idle, busy, draining, offline := 0, 0, 0, 0
	for _, wkr := range workers {
		switch wkr.Status {
		case domain.WorkerStatusIdle:
			idle++
		case domain.WorkerStatusBusy:
			busy++
		case domain.WorkerStatusDraining:
			draining++
		case domain.WorkerStatusOffline:
			offline++
		}
	}

	api.WriteSuccess(w, r, map[string]any{
		"workers": dtos,
		"total":   len(dtos),
		"summary": map[string]int{
			"idle":     idle,
			"busy":     busy,
			"draining": draining,
			"offline":  offline,
		},
	})
}

// Get returns a specific worker by ID.
// GET /workers/{workerId}
func (h *WorkersHandler) Get(w http.ResponseWriter, r *http.Request) {
	workerID := chi.URLParam(r, "workerId")
	if workerID == "" {
		api.WriteBadRequest(w, r, "worker ID is required")
		return
	}

	worker, err := h.workerService.GetWorker(r.Context(), workerID)
	if err != nil {
		if errors.Is(err, domain.ErrWorkerNotFound) {
			api.WriteNotFound(w, r, "worker not found: "+workerID)
			return
		}
		api.WriteInternalError(w, r, "failed to get worker")
		return
	}

	api.WriteSuccess(w, r, toWorkerDTO(worker))
}

// RegisterWorkerRequest is the request body for POST /workers/register.
type RegisterWorkerRequest struct {
	ID           string   `json:"id"`
	Hostname     string   `json:"hostname"`
	Version      string   `json:"version,omitempty"`
	Capabilities []string `json:"capabilities,omitempty"`
}

// Register handles worker self-registration.
// POST /workers/register
func (h *WorkersHandler) Register(w http.ResponseWriter, r *http.Request) {
	var req RegisterWorkerRequest
	if err := api.DecodeJSON(r, &req); err != nil {
		api.WriteBadRequest(w, r, "invalid request body")
		return
	}

	if req.ID == "" {
		api.WriteBadRequest(w, r, "worker id is required")
		return
	}
	if req.Hostname == "" {
		api.WriteBadRequest(w, r, "hostname is required")
		return
	}

	worker := &domain.Worker{
		ID:           req.ID,
		Hostname:     req.Hostname,
		Version:      req.Version,
		Capabilities: req.Capabilities,
	}

	if err := h.workerService.Register(r.Context(), worker); err != nil {
		api.WriteInternalError(w, r, "failed to register worker")
		return
	}

	api.WriteCreated(w, r, toWorkerDTO(worker))
}

// Heartbeat handles worker heartbeat.
// POST /workers/{workerId}/heartbeat
func (h *WorkersHandler) Heartbeat(w http.ResponseWriter, r *http.Request) {
	workerID := chi.URLParam(r, "workerId")
	if workerID == "" {
		api.WriteBadRequest(w, r, "worker ID is required")
		return
	}

	if err := h.workerService.Heartbeat(r.Context(), workerID); err != nil {
		if errors.Is(err, domain.ErrWorkerNotFound) {
			api.WriteNotFound(w, r, "worker not found: "+workerID)
			return
		}
		api.WriteInternalError(w, r, "failed to update heartbeat")
		return
	}

	api.WriteSuccess(w, r, map[string]any{
		"worker_id": workerID,
		"status":    "ok",
	})
}

// Drain sets a worker to draining status.
// POST /workers/{workerId}/drain
func (h *WorkersHandler) Drain(w http.ResponseWriter, r *http.Request) {
	workerID := chi.URLParam(r, "workerId")
	if workerID == "" {
		api.WriteBadRequest(w, r, "worker ID is required")
		return
	}

	if err := h.workerService.DrainWorker(r.Context(), workerID); err != nil {
		if errors.Is(err, domain.ErrWorkerNotFound) {
			api.WriteNotFound(w, r, "worker not found: "+workerID)
			return
		}
		api.WriteInternalError(w, r, "failed to drain worker")
		return
	}

	api.WriteSuccess(w, r, map[string]any{
		"worker_id": workerID,
		"status":    "draining",
		"message":   "worker will finish current task then stop accepting new work",
	})
}