package api

import (
	"context"
	"encoding/json"
	"net/http"

	"geniusrun/backend/internal/garmin"
	applog "geniusrun/backend/internal/log"
)

// detailFillBatchSize bounds how many activities' details/splits are fetched
// per sync trigger, matching the sequential rate-limited fetch in
// internal/sync.Service.FillPendingDetails.
const detailFillBatchSize = 50

type authResponse struct {
	Status  string `json:"status"` // "authenticated" | "mfa_required" | "failed"
	Message string `json:"message"`
}

func authStatusString(s garmin.AuthStatus) string {
	switch s {
	case garmin.AuthSuccess:
		return "authenticated"
	case garmin.AuthMFARequired:
		return "mfa_required"
	case garmin.AuthFailed:
		return "failed"
	default:
		return "unknown"
	}
}

// recordAuthResult updates the in-memory auth status/message for userID,
// and -- on a successful authentication -- persists that this account has
// connected to Garmin at least once (store.MarkGarminConnected), which is
// what the login gate actually checks (the in-memory auth status resets on
// every backend restart; this doesn't).
func (s *Server) recordAuthResult(ctx context.Context, userID int64, res garmin.AuthResult) {
	s.mu.Lock()
	s.userAuthStatus[userID] = res.Status
	s.userAuthMessage[userID] = res.Message
	s.mu.Unlock()

	if res.Status == garmin.AuthSuccess {
		if err := s.DB.MarkGarminConnected(ctx, userID); err != nil {
			applog.App("api.Server", "recordAuthResult").Error("mark garmin connected", "user_id", userID, "error", err)
		}
	}
}

func (s *Server) handleGarminAuthLogin(w http.ResponseWriter, r *http.Request) {
	userID := userIDFromContext(r.Context())
	client, err := s.clientFor(r.Context(), userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	res, err := client.Authenticate(r.Context())
	if err != nil {
		writeError(w, http.StatusBadGateway, err.Error())
		return
	}
	s.recordAuthResult(r.Context(), userID, res)
	writeJSON(w, http.StatusOK, authResponse{Status: authStatusString(res.Status), Message: res.Message})
}

func (s *Server) handleGarminAuthMFA(w http.ResponseWriter, r *http.Request) {
	userID := userIDFromContext(r.Context())
	var body struct {
		Code string `json:"code"`
	}
	if err := json.NewDecoder(r.Body).Decode(&body); err != nil {
		writeError(w, http.StatusBadRequest, "invalid request body")
		return
	}
	if body.Code == "" {
		writeError(w, http.StatusBadRequest, "code is required")
		return
	}

	client, err := s.clientFor(r.Context(), userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	res, err := client.CompleteMFA(r.Context(), body.Code)
	if err != nil {
		writeError(w, http.StatusBadGateway, err.Error())
		return
	}
	s.recordAuthResult(r.Context(), userID, res)
	writeJSON(w, http.StatusOK, authResponse{Status: authStatusString(res.Status), Message: res.Message})
}

func (s *Server) handleGarminAuthStatus(w http.ResponseWriter, r *http.Request) {
	userID := userIDFromContext(r.Context())
	s.mu.Lock()
	status, msg := s.userAuthStatus[userID], s.userAuthMessage[userID]
	s.mu.Unlock()
	writeJSON(w, http.StatusOK, authResponse{Status: authStatusString(status), Message: msg})
}

// handleGarminSyncRun does a full sync pass: Backfill first (resumes from the
// watermark, so widening the configured history horizon between clicks is
// picked up automatically), then IncrementalSync (catches anything new since
// the latest known activity), then fills in details for whatever's still
// missing them. Activities already fully processed are left untouched --
// see internal/sync.Service.FillPendingDetails. Recorded as a single
// FullSync run so "last sync" reports the combined activity count, not just
// whichever of Backfill/IncrementalSync happened to finish last.
func (s *Server) handleGarminSyncRun(w http.ResponseWriter, r *http.Request) {
	userID := userIDFromContext(r.Context())
	svc, err := s.syncFor(r.Context(), userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	ok := s.backgroundSync(userID, func(ctx context.Context) error {
		return svc.FullSync(ctx, detailFillBatchSize)
	})
	if !ok {
		writeError(w, http.StatusConflict, "a sync is already in progress")
		return
	}
	writeJSON(w, http.StatusAccepted, map[string]string{"status": "started"})
}

// handleGarminSyncReset wipes every synced activity (and its laps/samples/kind
// assignments) and rewinds the backfill watermark, so the next Sync Now
// performs a genuinely fresh pull from Garmin. Destructive -- the frontend
// gates this behind a confirmation.
func (s *Server) handleGarminSyncReset(w http.ResponseWriter, r *http.Request) {
	userID := userIDFromContext(r.Context())
	svc, err := s.syncFor(r.Context(), userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	ok := s.backgroundSync(userID, func(ctx context.Context) error {
		return svc.ResetAll(ctx)
	})
	if !ok {
		writeError(w, http.StatusConflict, "a sync is already in progress")
		return
	}
	writeJSON(w, http.StatusAccepted, map[string]string{"status": "started"})
}

func (s *Server) handleGarminSyncRuns(w http.ResponseWriter, r *http.Request) {
	userID := userIDFromContext(r.Context())
	runs, err := s.DB.ListSyncRuns(r.Context(), userID, 20)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	writeJSON(w, http.StatusOK, runs)
}

func (s *Server) handleGarminSyncStatus(w http.ResponseWriter, r *http.Request) {
	userID := userIDFromContext(r.Context())
	run, ok, err := s.DB.LatestSyncRun(r.Context(), userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	pendingDetails, err := s.DB.CountActivitiesMissingDetails(r.Context(), userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	pendingWorkouts, err := s.DB.CountActivitiesMissingWorkout(r.Context(), userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}

	s.mu.Lock()
	inProgress := s.userSyncRunning[userID]
	s.mu.Unlock()

	svc, err := s.syncFor(r.Context(), userID)
	if err != nil {
		writeError(w, http.StatusInternalServerError, err.Error())
		return
	}
	progress := svc.Progress()

	resp := map[string]any{
		"in_progress":                inProgress,
		"progress":                   progress,
		"activities_pending_details": pendingDetails,
		"workouts_pending":           pendingWorkouts,
	}
	if ok {
		resp["last_run"] = run
	}
	writeJSON(w, http.StatusOK, resp)
}