// Package handlers provides HTTP request handlers for the chat server.
package handlers

import (
	"context"
	"encoding/json"
	"errors"
	"log/slog"
	"net/http"
	"time"

	"git.eeqj.de/sneak/chat/internal/broker"
	"git.eeqj.de/sneak/chat/internal/config"
	"git.eeqj.de/sneak/chat/internal/db"
	"git.eeqj.de/sneak/chat/internal/globals"
	"git.eeqj.de/sneak/chat/internal/healthcheck"
	"git.eeqj.de/sneak/chat/internal/logger"
	"go.uber.org/fx"
)

var errUnauthorized = errors.New("unauthorized")

// Params defines the dependencies for creating Handlers.
type Params struct {
	fx.In

	Logger      *logger.Logger
	Globals     *globals.Globals
	Config      *config.Config
	Database    *db.Database
	Healthcheck *healthcheck.Healthcheck
}

const defaultIdleTimeout = 24 * time.Hour

// Handlers manages HTTP request handling.
type Handlers struct {
	params        *Params
	log           *slog.Logger
	hc            *healthcheck.Healthcheck
	broker        *broker.Broker
	cancelCleanup context.CancelFunc
}

// New creates a new Handlers instance.
func New(
	lifecycle fx.Lifecycle,
	params Params,
) (*Handlers, error) {
	hdlr := &Handlers{ //nolint:exhaustruct // cancelCleanup set in startCleanup
		params: &params,
		log:    params.Logger.Get(),
		hc:     params.Healthcheck,
		broker: broker.New(),
	}

	lifecycle.Append(fx.Hook{
		OnStart: func(ctx context.Context) error {
			hdlr.startCleanup(ctx)

			return nil
		},
		OnStop: func(_ context.Context) error {
			hdlr.stopCleanup()

			return nil
		},
	})

	return hdlr, nil
}

func (hdlr *Handlers) respondJSON(
	writer http.ResponseWriter,
	_ *http.Request,
	data any,
	status int,
) {
	writer.Header().Set(
		"Content-Type",
		"application/json; charset=utf-8",
	)
	writer.WriteHeader(status)

	if data != nil {
		err := json.NewEncoder(writer).Encode(data)
		if err != nil {
			hdlr.log.Error(
				"json encode error", "error", err,
			)
		}
	}
}

func (hdlr *Handlers) respondError(
	writer http.ResponseWriter,
	request *http.Request,
	msg string,
	status int,
) {
	hdlr.respondJSON(
		writer, request,
		map[string]string{"error": msg},
		status,
	)
}

func (hdlr *Handlers) idleTimeout() time.Duration {
	raw := hdlr.params.Config.SessionIdleTimeout
	if raw == "" {
		return defaultIdleTimeout
	}

	dur, err := time.ParseDuration(raw)
	if err != nil {
		hdlr.log.Error(
			"invalid SESSION_IDLE_TIMEOUT, using default",
			"value", raw, "error", err,
		)

		return defaultIdleTimeout
	}

	return dur
}

// startCleanup launches the idle-user cleanup goroutine.
// We use context.Background rather than the OnStart ctx
// because the OnStart context is startup-scoped and would
// cancel the goroutine once all start hooks complete.
//
//nolint:contextcheck // intentional Background ctx
func (hdlr *Handlers) startCleanup(_ context.Context) {
	cleanupCtx, cancel := context.WithCancel(
		context.Background(),
	)
	hdlr.cancelCleanup = cancel

	go hdlr.cleanupLoop(cleanupCtx)
}

func (hdlr *Handlers) stopCleanup() {
	if hdlr.cancelCleanup != nil {
		hdlr.cancelCleanup()
	}
}

func (hdlr *Handlers) cleanupLoop(ctx context.Context) {
	timeout := hdlr.idleTimeout()

	interval := max(timeout/2, time.Minute) //nolint:mnd // half the timeout

	ticker := time.NewTicker(interval)
	defer ticker.Stop()

	for {
		select {
		case <-ticker.C:
			hdlr.runCleanup(ctx, timeout)
		case <-ctx.Done():
			return
		}
	}
}

func (hdlr *Handlers) runCleanup(
	ctx context.Context,
	timeout time.Duration,
) {
	cutoff := time.Now().Add(-timeout)

	// Find sessions that will be orphaned so we can send
	// QUIT notifications before deleting anything.
	stale, err := hdlr.params.Database.
		GetStaleOrphanSessions(ctx, cutoff)
	if err != nil {
		hdlr.log.Error(
			"stale session lookup failed", "error", err,
		)
	}

	for _, ss := range stale {
		hdlr.cleanupUser(ctx, ss.ID, ss.Nick)
	}

	deleted, err := hdlr.params.Database.DeleteStaleUsers(
		ctx, cutoff,
	)
	if err != nil {
		hdlr.log.Error(
			"user cleanup failed", "error", err,
		)

		return
	}

	if deleted > 0 {
		hdlr.log.Info(
			"cleaned up stale users",
			"deleted", deleted,
		)
	}
}