package tickets

import (
	"bytes"
	"context"
	"fmt"
	"log"
	"time"

	"velox-bot/internal/db/repos/ticketrepo"

	"github.com/bwmarrin/discordgo"
)

// Actor is whoever pressed the button or ran the command, with their
// permissions in the ticket thread.
type Actor struct {
	Member *discordgo.Member
	Perms  int64
}

func (a Actor) userID() string {
	if a.Member == nil || a.Member.User == nil {
		return ""
	}
	return a.Member.User.ID
}

// load finds the open ticket behind a thread and its category (nil when the
// category was deleted since).
func load(ctx context.Context, st Store, threadID string) (*ticketrepo.Ticket, *ticketrepo.Category, error) {
	t, err := st.GetTicketByThread(ctx, mustID(threadID))
	if err != nil {
		return nil, nil, err
	}
	if t == nil {
		return nil, nil, ErrNotATicket
	}
	if t.Status != ticketrepo.StatusOpen {
		return nil, nil, ErrClosed
	}
	var cat *ticketrepo.Category
	if t.CategoryID != 0 {
		if cat, err = st.GetCategory(ctx, t.GuildID, t.CategoryID); err != nil {
			return nil, nil, err
		}
	}
	return t, cat, nil
}

// updateIntro edits the ticket's first message to show who claimed it and
// whether it is closed. It keeps the original text (the details are only in
// that message) and is best effort: a deleted first message doesn't stop the
// ticket from being claimed or closed.
func updateIntro(d Discord, t *ticketrepo.Ticket) {
	if t.IntroMessage == 0 {
		return
	}
	msg, err := d.ChannelMessage(id(t.ThreadID), id(t.IntroMessage))
	if err != nil || len(msg.Embeds) == 0 {
		return
	}
	fresh := IntroEmbed(t, "")
	e := *msg.Embeds[0]
	e.Color, e.Footer = fresh.Color, fresh.Footer
	e.Fields = fresh.Fields
	embeds := []*discordgo.MessageEmbed{&e}
	comps := IntroComponents(t.ClaimedBy != 0, t.Status == ticketrepo.StatusClosed)
	if _, err := d.ChannelMessageEditComplex(&discordgo.MessageEdit{
		Channel: id(t.ThreadID), ID: id(t.IntroMessage), Embeds: &embeds, Components: &comps,
	}); err != nil {
		log.Printf("tickets: updating the first message of ticket %d: %v", t.ID, err)
	}
}

// Claim marks the actor as the ticket's handler. Only staff can claim, and a
// claimed ticket stays with its first claimer.
func Claim(ctx context.Context, d Discord, st Store, threadID string, a Actor) error {
	t, cat, err := load(ctx, st, threadID)
	if err != nil {
		return err
	}
	if !IsStaff(a.Member, a.Perms, cat) {
		return ErrNotStaff
	}
	me := mustID(a.userID())
	holder, err := st.Claim(ctx, t.ThreadID, me)
	if err != nil {
		return err
	}
	if holder == 0 {
		return ErrClosed
	}
	if holder != me {
		return UserError(fmt.Sprintf("<@%d> is already handling this ticket.", holder))
	}
	t.ClaimedBy = me
	updateIntro(d, t)
	_, err = d.ChannelMessageSendComplex(id(t.ThreadID), &discordgo.MessageSend{
		Content:         fmt.Sprintf("<@%d> is handling this ticket.", me),
		AllowedMentions: &discordgo.MessageAllowedMentions{},
	})
	return err
}

// CheckCanClose runs before the close form is shown.
func CheckCanClose(ctx context.Context, st Store, threadID string, a Actor) error {
	t, cat, err := load(ctx, st, threadID)
	if err != nil {
		return err
	}
	if mustID(a.userID()) != t.OpenerID && !IsStaff(a.Member, a.Perms, cat) {
		return ErrNotInvolved
	}
	return nil
}

// Close closes the ticket: a note in the thread, a summary with the
// transcript in the log channel, the first message's buttons disabled, and
// the thread locked and archived. The opener or staff can close.
func Close(ctx context.Context, d Discord, st Store, threadID string, a Actor, reason string) error {
	t, cat, err := load(ctx, st, threadID)
	if err != nil {
		return err
	}
	me := mustID(a.userID())
	if me != t.OpenerID && !IsStaff(a.Member, a.Perms, cat) {
		return ErrNotInvolved
	}
	reason = clip(reason, maxReason)

	// The transcript is taken before anything else changes in the thread.
	transcript, count, terr := Transcript(d, t)

	closed, err := st.Close(ctx, t.ThreadID, me, reason)
	if err != nil {
		return err
	}
	if !closed {
		return ErrClosed // someone else closed it a moment ago
	}
	t.Status, t.ClosedBy, t.CloseReason, t.ClosedAt = ticketrepo.StatusClosed, me, reason, time.Now()

	note := fmt.Sprintf("🔒 Closed by <@%d>.", me)
	if reason != "" {
		note += " Reason: " + reason
	}
	if _, err := d.ChannelMessageSendComplex(id(t.ThreadID), &discordgo.MessageSend{
		Content: note, AllowedMentions: &discordgo.MessageAllowedMentions{},
	}); err != nil {
		log.Printf("tickets: posting the close note in ticket %d: %v", t.ID, err)
	}

	if terr != nil {
		log.Printf("tickets: transcript of ticket %d: %v", t.ID, terr)
	}
	postLog(ctx, d, st, t, transcript, count)
	updateIntro(d, t)

	yes := true
	if _, err := d.ChannelEditComplex(id(t.ThreadID), &discordgo.ChannelEdit{Locked: &yes, Archived: &yes}); err != nil {
		return fmt.Errorf("locking the thread: %w", err)
	}
	return nil
}

// postLog sends the closed ticket's summary and transcript to the log
// channel, if the guild has one.
func postLog(ctx context.Context, d Discord, st Store, t *ticketrepo.Ticket, transcript []byte, count int) {
	s, err := st.GetSettings(ctx, t.GuildID)
	if err != nil || s.LogChannelID == 0 {
		return
	}
	claimed := "Nobody"
	if t.ClaimedBy != 0 {
		claimed = "<@" + id(t.ClaimedBy) + ">"
	}
	reason := t.CloseReason
	if reason == "" {
		reason = "No reason given"
	}
	embed := &discordgo.MessageEmbed{
		Title:       fmt.Sprintf("Ticket #%04d closed · %s", t.Number, clip(t.CategoryName, 60)),
		Description: "**" + clip(t.Subject, maxSubject) + "**",
		Color:       accent,
		Fields: []*discordgo.MessageEmbedField{
			{Name: "Opened by", Value: "<@" + id(t.OpenerID) + ">", Inline: true},
			{Name: "Claimed by", Value: claimed, Inline: true},
			{Name: "Closed by", Value: "<@" + id(t.ClosedBy) + ">", Inline: true},
			{Name: "Reason", Value: clip(reason, 1024)},
			{Name: "Thread", Value: "<#" + id(t.ThreadID) + ">", Inline: true},
			{Name: "Messages", Value: fmt.Sprint(count), Inline: true},
			{Name: "Open for", Value: humanDuration(t.ClosedAt.Sub(t.CreatedAt)), Inline: true},
		},
		Timestamp: t.ClosedAt.UTC().Format(time.RFC3339),
	}
	send := &discordgo.MessageSend{Embeds: []*discordgo.MessageEmbed{embed}, AllowedMentions: &discordgo.MessageAllowedMentions{}}
	if len(transcript) > 0 {
		send.Files = []*discordgo.File{{
			Name:        fmt.Sprintf("ticket-%04d.txt", t.Number),
			ContentType: "text/plain; charset=utf-8",
			Reader:      bytes.NewReader(transcript),
		}}
	}
	if _, err := d.ChannelMessageSendComplex(id(s.LogChannelID), send); err != nil {
		log.Printf("tickets: posting ticket %d to the log channel: %v", t.ID, err)
	}
}

func humanDuration(d time.Duration) string {
	switch {
	case d <= 0:
		return "-"
	case d < time.Hour:
		return fmt.Sprintf("%d min", int(d.Minutes()+0.5))
	case d < 48*time.Hour:
		return fmt.Sprintf("%.1f h", d.Hours())
	default:
		return fmt.Sprintf("%.1f days", d.Hours()/24)
	}
}

// AddMember brings someone into a ticket. The opener and staff can add.
func AddMember(ctx context.Context, d Discord, st Store, threadID string, a Actor, userID string) error {
	t, cat, err := load(ctx, st, threadID)
	if err != nil {
		return err
	}
	if mustID(a.userID()) != t.OpenerID && !IsStaff(a.Member, a.Perms, cat) {
		return ErrNotInvolved
	}
	if err := d.ThreadMemberAdd(threadID, userID); err != nil {
		return fmt.Errorf("adding to the thread: %w", err)
	}
	_, err = d.ChannelMessageSendComplex(threadID, &discordgo.MessageSend{
		Content:         fmt.Sprintf("<@%s> added <@%s> to this ticket.", a.userID(), userID),
		AllowedMentions: &discordgo.MessageAllowedMentions{},
	})
	return err
}

// RemoveMember takes someone out of a ticket. Only staff can, and never the
// opener.
func RemoveMember(ctx context.Context, d Discord, st Store, threadID string, a Actor, userID string) error {
	t, cat, err := load(ctx, st, threadID)
	if err != nil {
		return err
	}
	if !IsStaff(a.Member, a.Perms, cat) {
		return ErrNotStaff
	}
	if mustID(userID) == t.OpenerID {
		return UserError("The person who opened the ticket can't be removed. Close the ticket instead.")
	}
	if err := d.ThreadMemberRemove(threadID, userID); err != nil {
		return fmt.Errorf("removing from the thread: %w", err)
	}
	_, err = d.ChannelMessageSendComplex(threadID, &discordgo.MessageSend{
		Content:         fmt.Sprintf("<@%s> removed <@%s> from this ticket.", a.userID(), userID),
		AllowedMentions: &discordgo.MessageAllowedMentions{},
	})
	return err
}

// ThreadDeleted closes the ticket of a thread someone deleted by hand, so it
// stops counting towards the opener's limit.
func ThreadDeleted(ctx context.Context, st Store, threadID string) {
	if _, err := st.Close(ctx, mustID(threadID), 0, "Thread deleted"); err != nil {
		log.Printf("tickets: closing the ticket of deleted thread %s: %v", threadID, err)
	}
}