package api

import (
	"context"
	"crypto/subtle"
	_ "embed"
	"encoding/json"
	"net/http"
	"strings"
	"time"

	"github.com/ponzischeme89/memby/server/internal/library"
	"github.com/ponzischeme89/memby/server/internal/store"
)

//go:embed admin.html
var adminPage []byte

// adminRoutes is the operator interface: library imports, the maintenance switch, and
// row engagement. Disabled entirely when MEMBY_ADMIN_TOKEN is unset, so it cannot be
// left exposed by accident.
func (s *Server) adminRoutes() http.Handler {
	mux := http.NewServeMux()

	mux.HandleFunc("GET /admin/{$}", s.handleAdminPage)
	mux.Handle("GET /admin/api/status", s.adminAuth(s.handleAdminStatus))
	mux.Handle("GET /admin/api/analytics", s.adminAuth(s.handleAdminAnalytics))
	mux.Handle("POST /admin/api/sync", s.adminAuth(s.handleAdminSync))
	mux.Handle("POST /admin/api/maintenance", s.adminAuth(s.handleAdminMaintenance))

	return mux
}

// adminAuth guards the admin API with a shared token, compared in constant time.
func (s *Server) adminAuth(h http.HandlerFunc) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		if s.cfg.AdminToken == "" {
			http.NotFound(w, r)
			return
		}
		presented := strings.TrimSpace(strings.TrimPrefix(r.Header.Get("Authorization"), "Bearer "))
		if subtle.ConstantTimeCompare([]byte(presented), []byte(s.cfg.AdminToken)) != 1 {
			writeError(w, http.StatusUnauthorized, "invalid admin token")
			return
		}
		h(w, r)
	})
}

func (s *Server) handleAdminPage(w http.ResponseWriter, r *http.Request) {
	if s.cfg.AdminToken == "" {
		http.NotFound(w, r)
		return
	}
	w.Header().Set("Content-Type", "text/html; charset=utf-8")
	// The page holds no secrets; the token is entered by the operator and kept in the
	// browser's local storage.
	w.Header().Set("Cache-Control", "no-store")
	_, _ = w.Write(adminPage)
}

type adminStatus struct {
	Maintenance store.Maintenance  `json:"maintenance"`
	Library     store.LibraryStats `json:"library"`
	SyncRunning bool               `json:"syncRunning"`
	Runs        []store.SyncRun    `json:"runs"`
	SyncEvery   string             `json:"syncEvery"`
}

func (s *Server) handleAdminStatus(w http.ResponseWriter, r *http.Request) {
	ctx := r.Context()

	stats, err := s.store.LibraryStats(ctx)
	if err != nil {
		s.log.Error("library stats failed", "error", err)
		writeError(w, http.StatusInternalServerError, "could not read library stats")
		return
	}
	runs, err := s.store.RecentSyncRuns(ctx, 10)
	if err != nil {
		s.log.Error("sync history failed", "error", err)
		writeError(w, http.StatusInternalServerError, "could not read sync history")
		return
	}

	writeJSON(w, http.StatusOK, adminStatus{
		Maintenance: s.maintenance.get(),
		Library:     stats,
		SyncRunning: s.syncer.Running(),
		Runs:        runs,
		SyncEvery:   s.cfg.SyncInterval.String(),
	})
}

type syncRequest struct {
	Kind string `json:"kind"`
}

// handleAdminSync starts an import in the background and returns immediately. A full
// import of a large library takes minutes; the page polls /admin/api/status for progress.
func (s *Server) handleAdminSync(w http.ResponseWriter, r *http.Request) {
	var req syncRequest
	if err := json.NewDecoder(http.MaxBytesReader(w, r.Body, 4<<10)).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "malformed request body")
		return
	}
	if req.Kind != "full" && req.Kind != "incremental" {
		writeError(w, http.StatusBadRequest, `kind must be "full" or "incremental"`)
		return
	}
	if s.syncer.Running() {
		writeError(w, http.StatusConflict, "a sync is already running")
		return
	}

	go func() {
		ctx, cancel := context.WithTimeout(context.WithoutCancel(context.Background()), s.cfg.SyncTimeout)
		defer cancel()
		if _, err := s.syncer.Sync(ctx, req.Kind, "manual"); err != nil {
			s.log.Error("manual sync failed", "kind", req.Kind, "error", err)
		}
	}()

	writeJSON(w, http.StatusAccepted, map[string]string{"status": "started", "kind": req.Kind})
}

type maintenanceRequest struct {
	Enabled bool   `json:"enabled"`
	Message string `json:"message"`
}

func (s *Server) handleAdminMaintenance(w http.ResponseWriter, r *http.Request) {
	var req maintenanceRequest
	if err := json.NewDecoder(http.MaxBytesReader(w, r.Body, 4<<10)).Decode(&req); err != nil {
		writeError(w, http.StatusBadRequest, "malformed request body")
		return
	}

	state := store.Maintenance{Enabled: req.Enabled, Message: strings.TrimSpace(req.Message)}
	if err := s.store.SetMaintenance(r.Context(), state); err != nil {
		s.log.Error("maintenance write failed", "error", err)
		writeError(w, http.StatusInternalServerError, "could not update maintenance mode")
		return
	}
	if err := s.LoadMaintenance(r.Context()); err != nil {
		s.log.Warn("maintenance reload failed", "error", err)
	}

	s.log.Warn("maintenance mode changed", "enabled", state.Enabled, "message", state.Message)
	writeJSON(w, http.StatusOK, s.maintenance.get())
}

func (s *Server) handleAdminAnalytics(w http.ResponseWriter, r *http.Request) {
	days := queryInt(r, "days", 7, 90)
	since := time.Now().UTC().AddDate(0, 0, -days)

	stats, err := s.store.RowStats(r.Context(), since)
	if err != nil {
		s.log.Error("row stats failed", "error", err)
		writeError(w, http.StatusInternalServerError, "could not read analytics")
		return
	}
	writeJSON(w, http.StatusOK, map[string]any{"days": days, "rows": stats})
}

// syncerHandle is the slice of the syncer the API needs, so api does not depend on the
// concrete type for testing.
type syncerHandle interface {
	Running() bool
	Sync(ctx context.Context, kind, trigger string) (library.Result, error)
}