// Package api is geniusrun's HTTP layer: REST handlers over internal/store,
// internal/garmin, and internal/sync.
package api

import (
	"context"
	"crypto/sha256"
	"encoding/hex"
	"encoding/json"
	"fmt"
	applog "geniusrun/backend/internal/log"
	"log/slog"
	"net/http"
	"os"
	"path/filepath"
	"strconv"
	"sync"
	"sync/atomic"
	"time"

	"geniusrun/backend/internal/auth"
	"geniusrun/backend/internal/garmin"
	"geniusrun/backend/internal/store"

	"github.com/go-chi/chi/v5"
	"github.com/go-chi/chi/v5/middleware"
)

// Server wires the HTTP handlers to the app's dependencies. garmin.Client
// and sync.Service are per-user (each user might have their own Garmin
// account), built lazily on first use via GarminFactory and cached.
type Server struct {
	DB            *store.DB
	Auth          auth.Verifier
	SessionConfig SessionConfig

	// GarminFactory builds a real (or fake, in tests) garmin.Client from a
	// fully-resolved per-user Config. Production wiring passes
	// garmin.NewClient; tests inject a factory returning a shared
	// *mock.Client (see newTestServer in api_test.go).
	GarminFactory func(garmin.ClientConfig) garmin.Client

	// ClientConfig holds the plumbing shared by every user's garmin.Config
	// (the python interpreter path + the token-store root directory); only
	// GarminEmail/GarminPassword/TokenStorePath vary per user, filled in by
	// garminFor.
	ClientConfig garmin.ClientConfig
	SyncConfig   garmin.SyncConfig

	// EnvVars is the read-only, display-safe environment-configuration
	// snapshot served by GET /api/config -- built once in main.go from
	// config.Config.DisplayEnv() (secrets already masked there); handlers
	// never call os.Getenv.
	EnvVars []EnvVar

	mu              sync.Mutex
	userClient      map[int64]garmin.Client
	userSync        map[int64]*garmin.Sync
	userAuthStatus  map[int64]garmin.AuthStatus
	userAuthMessage map[int64]string
	userSyncRunning map[int64]bool
	setupSession    map[string]*setupSession
}

// NewServer builds a Server.
func NewServer(db *store.DB, garminFactory func(garmin.ClientConfig) garmin.Client, garminBase garmin.ClientConfig, syncConfig garmin.SyncConfig, authVerifier auth.Verifier, sessionConfig SessionConfig) *Server {
	return &Server{
		DB:              db,
		GarminFactory:   garminFactory,
		ClientConfig:    garminBase,
		SyncConfig:      syncConfig,
		Auth:            authVerifier,
		SessionConfig:   sessionConfig,
		userClient:      map[int64]garmin.Client{},
		userSync:        map[int64]*garmin.Sync{},
		userAuthStatus:  map[int64]garmin.AuthStatus{},
		userAuthMessage: map[int64]string{},
		userSyncRunning: map[int64]bool{},
		setupSession:    map[string]*setupSession{},
	}
}

// Router builds the HTTP routes.
func (s *Server) Router() http.Handler {
	r := chi.NewRouter()
	r.Use(loggingMiddleware)
	r.Use(corsMiddleware)
	r.Route("/api", func(r chi.Router) {
		r.Get("/health", s.handleHealth)

		// Unprotected: these two ARE the login flow, so they can't require
		// a session yet.
		r.Get("/session/login", s.handleSessionLogin)
		r.Get("/session/callback", s.handleSessionCallback)

		r.Group(func(r chi.Router) {
			r.Use(auth.RequireSession(s.SessionConfig.Secret))
			r.Use(s.resolveUser)

			r.Get("/session/me", s.handleSessionMe)
			r.Post("/session/logout", s.handleSessionLogout)

			r.Route("/setup", func(r chi.Router) {
				r.Post("/complete", s.handleSetupComplete)
				r.Route("/garmin", func(r chi.Router) {
					r.Post("/login", s.handleSetupGarminLogin)
					r.Post("/mfa", s.handleSetupGarminMFA)
				})
			})

			r.Group(func(r chi.Router) {
				r.Use(requireProvisionedUser)

				r.Route("/profile", func(r chi.Router) {
					r.Get("/", s.handleGetProfile)
					r.Put("/", s.handleUpdateProfile)
					r.Delete("/", s.handleDeleteProfile)
				})

				r.Route("/garmin", func(r chi.Router) {
					r.Route("/auth", func(r chi.Router) {
						r.Post("/login", s.handleGarminAuthLogin)
						r.Post("/mfa", s.handleGarminAuthMFA)
						r.Get("/status", s.handleGarminAuthStatus)
					})

					r.Route("/sync", func(r chi.Router) {
						r.Post("/run", s.handleGarminSyncRun)
						r.Post("/reset", s.handleGarminSyncReset)
						r.Get("/runs", s.handleGarminSyncRuns)
						r.Get("/status", s.handleGarminSyncStatus)
					})

				})

				r.Route("/activities", func(r chi.Router) {
					r.Get("/", s.handleListActivities)
					r.Post("/{activityID}/assign", s.handleAssignActivity)
					r.Post("/{activityID}/unlock", s.handleUnlockActivity)
					r.Post("/{activityID}/unassign", s.handleUnassignActivity)
				})

				r.Route("/workout-kinds", func(r chi.Router) {
					r.Get("/", s.handleListWorkoutKinds)
					r.Get("/{id}", s.handleGetWorkoutKind)
					r.Put("/{id}", s.handleUpdateWorkoutKind)
				})

				r.Post("/reclassify", s.handleReclassifyAll)

				r.Get("/config", s.handleGetConfig)
				r.Put("/config", s.handlePutConfig)

				r.Get("/progression/{kindID}", s.handleProgression)
			})
		})
	})
	return r
}

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

var requestIDCounter atomic.Int64

// loggingMiddleware logs one JSON line per HTTP request (method,
// path, status, duration) and attaches a per-request logger (tagged with a
// request_id) to the request context, so any downstream call this request
// triggers -- e.g. a Garmin wrapper round-trip -- logs with the same
// correlating id (see internal/applog, internal/garmin's roundTrip).
func loggingMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		id := fmt.Sprintf("req-%d", requestIDCounter.Add(1))
		logger := applog.FromContext(r.Context()).With("request_id", id)
		r = r.WithContext(applog.WithLogger(r.Context(), logger))

		ww := middleware.NewWrapResponseWriter(w, r.ProtoMajor)
		start := time.Now()
		next.ServeHTTP(ww, r)

		level := slog.LevelInfo
		if ww.Status() >= 500 {
			level = slog.LevelWarn
		}
		logger.LogAttrs(r.Context(), level, "HTTP request",
			slog.String("method", r.Method),
			slog.String("path", r.URL.Path),
			slog.Int("status", ww.Status()),
			slog.Int64("duration_ms", time.Since(start).Milliseconds()),
		)
	})
}

// corsMiddleware allows the frontend dev server (a different port) to call
// this API. Reflecting any origin back is safe even with credentials
// enabled: this remains a single-operator app whose real access control is
// the OIDC login gate (internal/auth), not origin-based CSRF defense.
func corsMiddleware(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if origin := r.Header.Get("Origin"); origin != "" {
			w.Header().Set("Access-Control-Allow-Origin", origin)
			w.Header().Set("Access-Control-Allow-Methods", "GET, POST, PUT, DELETE, OPTIONS")
			w.Header().Set("Access-Control-Allow-Headers", "Content-Type")
			w.Header().Set("Access-Control-Allow-Credentials", "true")
		}
		if r.Method == http.MethodOptions {
			w.WriteHeader(http.StatusNoContent)
			return
		}
		next.ServeHTTP(w, r)
	})
}

// clientFor returns userID's garmin.Client, building and caching it (from
// userID's own profile row) on first use.
func (s *Server) clientFor(ctx context.Context, userID int64) (garmin.Client, error) {
	s.mu.Lock()
	if c, ok := s.userClient[userID]; ok {
		s.mu.Unlock()
		return c, nil
	}
	s.mu.Unlock()

	profile, err := s.DB.GetProfile(ctx, userID)
	if err != nil {
		return nil, fmt.Errorf("load profile for garmin client (user %d): %w", userID, err)
	}
	cfg := s.ClientConfig
	cfg.GarminEmail = profile.GarminEmail
	cfg.GarminPassword = profile.GarminPassword
	if cfg.TokenStorePath != "" {
		cfg.TokenStorePath = filepath.Join(cfg.TokenStorePath, strconv.FormatInt(userID, 10))
	}

	s.mu.Lock()
	defer s.mu.Unlock()
	if c, ok := s.userClient[userID]; ok {
		return c, nil // built concurrently by another request between our unlock and re-lock
	}
	client := s.GarminFactory(cfg)
	s.userClient[userID] = client
	return client, nil
}

// removeUserClient drops userID's cached garmin.Client/sync.Service (if
// any) and every other per-user in-memory entry for userID, terminating the
// client's subprocess and best-effort removing its on-disk token-store
// directory. Called when a user's account has just been deleted from the
// DB, so nothing in memory keeps referencing a userID that no longer
// exists.
func (s *Server) removeUserClient(userID int64) {
	s.mu.Lock()
	client, ok := s.userClient[userID]
	delete(s.userClient, userID)
	delete(s.userSync, userID)
	delete(s.userAuthStatus, userID)
	delete(s.userAuthMessage, userID)
	delete(s.userSyncRunning, userID)
	s.mu.Unlock()

	if ok {
		if err := client.Close(); err != nil {
			slog.Error("close garmin client for deleted user", "user_id", userID, "error", err)
		}
	}
	if s.ClientConfig.TokenStorePath == "" {
		return
	}
	tokenStoreDir := filepath.Join(s.ClientConfig.TokenStorePath, strconv.FormatInt(userID, 10))
	if err := os.RemoveAll(tokenStoreDir); err != nil {
		slog.Error("remove token store dir for deleted user", "user_id", userID, "error", err)
	}
}

// syncFor returns userID's sync.Service, building and caching it on first use.
func (s *Server) syncFor(ctx context.Context, userID int64) (*garmin.Sync, error) {
	s.mu.Lock()
	if svc, ok := s.userSync[userID]; ok {
		s.mu.Unlock()
		return svc, nil
	}
	s.mu.Unlock()

	client, err := s.clientFor(ctx, userID)
	if err != nil {
		return nil, err
	}

	s.mu.Lock()
	defer s.mu.Unlock()
	if svc, ok := s.userSync[userID]; ok {
		return svc, nil
	}
	svc := garmin.NewSync(client, s.DB, userID, s.SyncConfig, nil)
	s.userSync[userID] = svc
	return svc, nil
}

// backgroundSync runs fn in a goroutine with a fresh context, guarded so
// only one sync operation per userID runs at a time. Returns false if one
// is already in progress for that user.
func (s *Server) backgroundSync(userID int64, fn func(ctx context.Context) error) bool {
	s.mu.Lock()
	if s.userSyncRunning[userID] {
		s.mu.Unlock()
		return false
	}
	s.userSyncRunning[userID] = true
	s.mu.Unlock()

	go func() {
		defer func() {
			s.mu.Lock()
			s.userSyncRunning[userID] = false
			s.mu.Unlock()
		}()
		if err := fn(context.Background()); err != nil {
			slog.Error("background sync failed", "user_id", userID, "error", err)
		}
	}()
	return true
}

// setupTokenStoreDir returns the token-store directory an ephemeral setup
// session for sub should use -- hashed rather than sub itself, since sub is
// an opaque string from the identity provider and using it verbatim in a
// filesystem path would be a directory-traversal risk if it ever contained
// path separators.
func setupTokenStoreDir(root, sub string) string {
	h := sha256.Sum256([]byte(sub))
	return filepath.Join(root, "setup", hex.EncodeToString(h[:]))
}

func writeJSON(w http.ResponseWriter, status int, v any) {
	w.Header().Set("Content-Type", "application/json")
	w.WriteHeader(status)
	if err := json.NewEncoder(w).Encode(v); err != nil {
		slog.Error("encode response", "error", err)
	}
}

func writeError(w http.ResponseWriter, status int, msg string) {
	writeJSON(w, status, map[string]string{"error": msg})
}