package main

import (
	"context"
	"crypto/sha256"
	"fmt"
	"log/slog"
	"slices"
	"strings"
	"sync"
	"time"

	"go.mau.fi/whatsmeow/store"
	"go.mau.fi/whatsmeow/types"
	"go.mau.fi/whatsmeow/types/events"
)

const (
	// whatsappSource is the source of the work events of the batches.
	whatsappSource = "whatsapp"

	// whatsappCatchupLimit is the longest wait for the end of the catch-up
	// after a connection.
	whatsappCatchupLimit = time.Minute
)

// newWhatsAppInbox returns the inbox of the batches in state, with clock for
// the times of the batch texts and groups for the names of the groups. images
// holds shared images, and logger gets image failures.
func newWhatsAppInbox(state *WhatsAppState, clock func() time.Time, groups *WhatsAppGroups, images *ImageStore, logger *slog.Logger) *WhatsAppInbox {
	return &WhatsAppInbox{
		state:        state,
		clock:        clock,
		groups:       groups,
		images:       images,
		logger:       logger,
		lookupTime:   whatsappLookupTime,
		imageTime:    whatsappImageTime,
		catchupLimit: whatsappCatchupLimit,
		wake:         make(chan struct{}, 1),
		failures:     make(chan error, 1),
	}
}

// WhatsAppInbox puts messages into batches, one chat at a time, as
// WhatsAppState says. deliver logs each closed batch as a work message that
// starts with [WhatsApp], and a batch that needs the user wakes the turn loop.
//
// After each connection, the servers send the messages that came while the
// daemon was away, and then OfflineSyncCompleted. Until then, or until
// catchupLimit passes, the closed batches wait in the state file. At the end of
// the catch-up, deliver closes all batches and logs them. It wakes the root
// once for its batches, so their catch-up gives one turn, not one for each
// chat. The batches of the state file at the start wait for the first catch-up
// in the same way. The event handler acknowledges a message only after the
// state file holds it, so the servers send again a message that a crash lost. A
// batch leaves the state file only after its work message is durable in the log
// or agent queue. A crash between the two can repeat an unrouted batch once. A
// routed batch enters the durable agent queue, which prevents a second log
// entry and wakes only the child. A missing child uses the root.
//
// The state file is the one of WhatsApp, which keeps the send records in it
// too. groups gives the names of the groups. The mutex protects the state of
// the catch-up, which the event handler of the library changes from its own
// goroutines. wake tells Run that a batch can be due or that a catch-up ended,
// and failures gives Run the error of a write of the state file.
type WhatsAppInbox struct {
	state        *WhatsAppState
	clock        func() time.Time
	groups       *WhatsAppGroups
	images       *ImageStore
	logger       *slog.Logger
	lookupTime   time.Duration
	imageTime    time.Duration
	catchupLimit time.Duration
	wake         chan struct{}
	failures     chan error

	mutex        sync.Mutex
	catchingUp   bool
	caughtUp     bool
	catchups     int
	catchupTimer *time.Timer
}

// due returns a channel that gets a value when the next open batch is due, or
// nil when no batch is open.
func (i *WhatsAppInbox) due() <-chan time.Time {
	wait, open := i.state.Wait(time.Now())
	if !open {
		return nil
	}

	return time.After(wait)
}

// deliver logs the closed batches in l in order, each as a work message of
// whatsappSource, and wakes the loop once with the batches that start a turn. A
// batch leaves the state file after its message is durable in the log. A group
// with no name gets its name from WhatsApp first, with the client of link.
// During a catch-up it logs nothing, and at its end it closes all batches
// first. With all, it closes and logs all batches also during a catch-up.
// Routed batches enter the durable child queue instead of the root log and wake
// their child even when the batch does not need a root turn.
func (i *WhatsAppInbox) deliver(ctx context.Context, l *TurnLoop, link WhatsAppLink, all bool) error {
	i.mutex.Lock()

	catchingUp := i.catchingUp
	caughtUp := i.caughtUp
	i.caughtUp = false
	i.mutex.Unlock()

	var err error

	switch {
	case all || caughtUp:
		err = i.state.CloseAll()
	case catchingUp:
		return nil
	default:
		_, err = i.state.CloseDue(time.Now())
	}

	if err != nil {
		return err
	}

	batches := i.state.Closed()
	if l.messages != nil {
		err = l.messages.PruneWhatsApp(batches)
		if err != nil {
			return fmt.Errorf("prune WhatsApp receipts: %w", err)
		}
	}

	var turns []Message

	for _, batch := range batches {
		if batch.Chat.Group && batch.Chat.Name == "" {
			batch.Chat.Name = i.groups.name(ctx, link, batch.Chat.ID)
		}

		text := batch.Text(i.clock().Location())
		if l.messages != nil {
			routed, err := l.messages.RouteWhatsApp(batch, text)
			if err != nil {
				return fmt.Errorf("route a WhatsApp batch: %w", err)
			}

			if routed {
				err = i.state.Remove(batch.Number)
				if err != nil {
					return fmt.Errorf("remove routed WhatsApp batch: %w", err)
				}

				continue
			}
		}

		message, err := l.Work(whatsappSource, text, "")
		if err != nil {
			return fmt.Errorf("log a WhatsApp batch: %w", err)
		}

		// A stop of the daemon during the flush is no failure: the
		// batch stays in the state file and repeats once at the next
		// start.
		err = l.Flush(ctx)
		if ctx.Err() != nil {
			return nil
		}

		if err != nil {
			return fmt.Errorf("log a WhatsApp batch: %w", err)
		}

		err = i.state.Remove(batch.Number)
		if err != nil {
			return err
		}

		if batch.Turn() {
			turns = append(turns, message)
		}
	}

	l.Wake(turns...)

	if l.messages != nil {
		err = l.messages.PruneWhatsApp(i.state.Closed())
		if err != nil {
			return fmt.Errorf("prune WhatsApp receipts: %w", err)
		}
	}

	return nil
}

// waitForCatchup makes the batches wait for a catch-up, as for the batches of
// the state file at the start, before the first connection.
func (i *WhatsAppInbox) waitForCatchup() {
	i.mutex.Lock()
	defer i.mutex.Unlock()

	i.catchingUp = true
}

// startCatchup starts the catch-up of a new connection, which ends at
// endCatchup or after catchupLimit.
func (i *WhatsAppInbox) startCatchup() {
	i.mutex.Lock()
	defer i.mutex.Unlock()

	i.catchingUp = true
	i.catchups++
	catchups := i.catchups
	if i.catchupTimer != nil {
		i.catchupTimer.Stop()
	}

	i.catchupTimer = time.AfterFunc(i.catchupLimit, func() {
		i.caughtUpBy(catchups)
	})
}

// receive stores an image before its batch and wakes Run. link gives the device
// and the own IDs. It returns false when the state file cannot hold the
// message, so that the library does not acknowledge it, and Run stops the
// daemon. An image that cannot be downloaded or stored gets a text marker. A
// message that the batches do not take is handled with nothing to do.
func (i *WhatsAppInbox) receive(link WhatsAppLink, event *events.Message) bool {
	ctx, cancel := context.WithTimeout(context.Background(), i.lookupTime)
	defer cancel()

	chat, message, found := whatsappMessage(ctx, link.device, link.own, event)
	if !found {
		return true
	}

	if event.Message.GetImageMessage() != nil {
		ctx, cancel := context.WithTimeout(context.Background(), i.imageTime)
		defer cancel()

		message.Text = i.imageText(ctx, link, event, message.Text)
	}

	_, err := i.state.Add(chat, message, time.Now())
	if err != nil {
		select {
		case i.failures <- err:
		default:
		}

		return false
	}

	select {
	case i.wake <- struct{}{}:
	default:
	}

	return true
}

// imageText stores the image of event before returning its marker and caption.
// Failures keep the caption with a text marker. The daemon log identifies the
// chat by a short hash, not its phone number.
func (i *WhatsAppInbox) imageText(ctx context.Context, link WhatsAppLink, event *events.Message, caption string) string {
	name, err := whatsappImage(ctx, link.client, i.images, event.Message.GetImageMessage())
	if err != nil {
		chat := event.Info.Chat.ToNonAD()
		digest := sha256.Sum256([]byte(chat.String()))
		redact := append(slices.Clone(link.own), chat.User)
		i.logger.Error("image receive failed", "chat", fmt.Sprintf("%x", digest[:6]), "err", whatsappRedact(redact, err.Error()))

		text := "(image not downloaded)"
		if caption != "" {
			text += "\n" + caption
		}

		return text
	}

	return imageText([]string{name}, caption)
}

// caughtUpBy ends the catch-up of the connection with the number catchups, when
// no later connection started a new one.
func (i *WhatsAppInbox) caughtUpBy(catchups int) {
	i.mutex.Lock()
	defer i.mutex.Unlock()

	if i.catchups == catchups {
		i.finishCatchup()
	}
}

// finishCatchup ends a running catch-up and wakes Run, which logs all batches.
// The caller holds the mutex.
func (i *WhatsAppInbox) finishCatchup() {
	if !i.catchingUp {
		return
	}

	i.catchingUp = false
	i.caughtUp = true
	if i.catchupTimer != nil {
		i.catchupTimer.Stop()
	}

	select {
	case i.wake <- struct{}{}:
	default:
	}
}

// endCatchup ends a running catch-up at OfflineSyncCompleted.
func (i *WhatsAppInbox) endCatchup() {
	i.mutex.Lock()
	defer i.mutex.Unlock()

	i.finishCatchup()
}

// stopCatchup ends a running catch-up with no wake, after the session is
// removed.
func (i *WhatsAppInbox) stopCatchup() {
	i.mutex.Lock()
	defer i.mutex.Unlock()

	i.catchingUp = false
}

// close stops the timer of the catch-up.
func (i *WhatsAppInbox) close() {
	i.mutex.Lock()
	defer i.mutex.Unlock()

	if i.catchupTimer != nil {
		i.catchupTimer.Stop()
	}
}

// whatsappMessage returns the chat and the batch message of event, or false
// when the batches do not take it. device is the linked device, and own holds
// the own IDs. The batches take text, images, and media markers from a private
// chat or a group, from another person or from the user. They do not take
// reactions, edits, deletions, view-once and disappearing messages, old
// history, status broadcasts, channels, and the chat of the user with itself.
//
// A mention of the user becomes @you, another mention @NAME when the name is
// known, and the own number and LID become OWN, so that they never go to the
// log.
func whatsappMessage(ctx context.Context, device *store.Device, own []string, event *events.Message) (WhatsAppChat, WhatsAppMessage, bool) {
	info := event.Info
	chatJID := info.Chat.ToNonAD()
	switch {
	case device == nil:
	case event.IsEdit, info.Edit != "", event.IsEphemeral, event.IsViewOnce, event.Message.GetImageMessage().GetViewOnce(), event.Message.GetVideoMessage().GetViewOnce(), event.SourceWebMsg != nil:
	case chatJID.Server != types.DefaultUserServer && chatJID.Server != types.HiddenUserServer && chatJID.Server != types.GroupServer:
	case slices.Contains(own, chatJID.User):
	default:
		return whatsappText(ctx, device, own, event)
	}

	return WhatsAppChat{}, WhatsAppMessage{}, false
}

// whatsappText returns the chat and the batch message of event, a message that
// the batches take. An image returns its caption until receive stores it.
func whatsappText(ctx context.Context, device *store.Device, own []string, event *events.Message) (WhatsAppChat, WhatsAppMessage, bool) {
	info := event.Info
	text := event.Message.GetConversation()
	extended := event.Message.GetExtendedTextMessage()
	if text == "" {
		text = extended.GetText()
	}

	contextInfo := extended.GetContextInfo()
	switch {
	case event.Message.GetImageMessage() != nil:
		image := event.Message.GetImageMessage()
		text = image.GetCaption()
		contextInfo = image.GetContextInfo()
	case event.Message.GetStickerMessage() != nil:
		text = "(sticker)"
		contextInfo = event.Message.GetStickerMessage().GetContextInfo()
	case event.Message.GetVideoMessage() != nil:
		video := event.Message.GetVideoMessage()
		text = "(video)"
		if video.GetGifPlayback() {
			text = "(GIF)"
		}

		if video.GetCaption() != "" {
			text += "\n" + video.GetCaption()
		}

		contextInfo = video.GetContextInfo()
	default:
		if strings.TrimSpace(text) == "" {
			return WhatsAppChat{}, WhatsAppMessage{}, false
		}
	}

	message := WhatsAppMessage{
		ID:   info.ID,
		Time: info.Timestamp,
		Mine: info.IsFromMe,
	}

	if !message.Mine {
		message.Sender = whatsappContactName(ctx, device, info.Sender, info.PushName)
	}

	for _, mentioned := range contextInfo.GetMentionedJID() {
		jid, err := types.ParseJID(mentioned)
		switch {
		case err != nil:
		case slices.Contains(own, jid.User):
			message.Mention = true
			text = strings.ReplaceAll(text, "@"+jid.User, "@you")
		default:
			text = strings.ReplaceAll(text, "@"+jid.User, "@"+whatsappContactName(ctx, device, jid, ""))
		}
	}

	participant, err := types.ParseJID(contextInfo.GetParticipant())
	message.Reply = err == nil && slices.Contains(own, participant.User)

	message.Text = whatsappRedact(own, text)
	chatJID := info.Chat.ToNonAD()
	chat := WhatsAppChat{
		ID:    chatJID.String(),
		Group: chatJID.Server == types.GroupServer,
	}

	if !chat.Group {
		push := info.PushName
		if message.Mine {
			push = ""
		}

		chat.Name = whatsappContactName(ctx, device, chatJID, push)
	}

	return chat, message, true
}