package discord

import (
	"context"
	"database/sql"
	"errors"
	"fmt"
	"log"
	"strings"
	"time"

	"github.com/bwmarrin/discordgo"

	"plumber/internal/mail"
	"plumber/internal/store"
)

const inboundBodyLimit = 12000

type inboundMessage struct {
	ID                  string
	ChannelID           string
	GuildID             string
	AuthorID            string
	Content             string
	ReferencedMessageID string
	Bot                 bool
	Attachments         int
}

func parseAdminMap(raw string) map[string]string {
	out := map[string]string{}
	for _, part := range strings.Split(raw, ",") {
		part = strings.TrimSpace(part)
		if part == "" {
			continue
		}
		id, username, ok := strings.Cut(part, ":")
		id = strings.TrimSpace(id)
		username = store.NormalizeUsername(username)
		if !ok || id == "" || username == "" {
			log.Printf("discord: skip invalid DISCORD_ADMIN_MAP entry %q", part)
			continue
		}
		out[id] = username
	}
	return out
}

func (b *Bot) onMessageCreate(_ *discordgo.Session, m *discordgo.MessageCreate) {
	if b == nil || m == nil || m.Author == nil {
		return
	}
	in := inboundMessage{
		ID:          m.ID,
		ChannelID:   m.ChannelID,
		GuildID:     m.GuildID,
		AuthorID:    m.Author.ID,
		Content:     m.Content,
		Bot:         m.Author.Bot,
		Attachments: len(m.Attachments),
	}
	if m.MessageReference != nil {
		in.ReferencedMessageID = m.MessageReference.MessageID
	}
	b.handleInbound(in)
}

func (b *Bot) handleInbound(in inboundMessage) {
	if b == nil || b.store == nil {
		return
	}
	if in.Bot || strings.TrimSpace(in.GuildID) == "" {
		return
	}
	if b.botUserID != "" && in.AuthorID == b.botUserID {
		return
	}
	body := strings.TrimSpace(in.Content)
	if in.Attachments > 0 {
		log.Printf("discord: ignoring %d attachment(s) on %s", in.Attachments, in.ID)
	}
	if body == "" {
		return
	}
	ctx, cancel := context.WithTimeout(context.Background(), discordTimeout)
	defer cancel()
	if !b.knownChannel(ctx, in.ChannelID) {
		return
	}
	username := b.admins[in.AuthorID]
	if username == "" {
		return
	}
	author, err := b.store.UserByUsername(ctx, username)
	if err != nil {
		if !errors.Is(err, sql.ErrNoRows) {
			log.Printf("discord: inbound author %s: %v", username, err)
		}
		return
	}
	if !author.Admin() {
		log.Printf("discord: inbound %s is not an admin", username)
		return
	}
	parent, root, err := b.inboundParent(ctx, in)
	if err != nil {
		if !errors.Is(err, sql.ErrNoRows) {
			log.Printf("discord: inbound parent %s: %v", in.ID, err)
		}
		return
	}
	if root.PostState == store.PostStateHidden {
		return
	}
	reply := &store.Post{
		AuthorID: author.ID,
		Body:     truncateRunes(body, inboundBodyLimit),
		ParentID: &parent.ID,
	}
	if err := b.store.CreatePost(ctx, reply); err != nil {
		log.Printf("discord: create inbound %s: %v", in.ID, err)
		return
	}
	if err := b.links.Upsert(ctx, store.DiscordLink{
		PostID:    reply.ID,
		MessageID: in.ID,
	}); err != nil {
		log.Printf("discord: save inbound link %s: %v", reply.ID, err)
	}
	b.notifyInboundReply(parent, root, reply, author)
	log.Printf("discord: inbound reply %s -> post %s", in.ID, reply.ID)
}

func (b *Bot) knownChannel(ctx context.Context, channelID string) bool {
	if strings.TrimSpace(channelID) == "" {
		return false
	}
	if channelID == b.channelID {
		return true
	}
	_, err := b.links.GetRootByThreadID(ctx, channelID)
	return err == nil
}

func (b *Bot) inboundParent(ctx context.Context, in inboundMessage) (*store.Post, *store.Post, error) {
	if ref := strings.TrimSpace(in.ReferencedMessageID); ref != "" {
		link, err := b.links.GetByMessageID(ctx, ref)
		if err == nil {
			return b.postAndRoot(ctx, link.PostID)
		}
		if !errors.Is(err, sql.ErrNoRows) {
			return nil, nil, err
		}
	}
	link, err := b.links.GetRootByThreadID(ctx, in.ChannelID)
	if err != nil {
		return nil, nil, err
	}
	return b.postAndRoot(ctx, link.PostID)
}

func (b *Bot) postAndRoot(ctx context.Context, postID string) (*store.Post, *store.Post, error) {
	postID = strings.TrimSpace(postID)
	if postID == "" {
		return nil, nil, sql.ErrNoRows
	}
	post, err := b.store.GetPost(ctx, postID)
	if err != nil {
		return nil, nil, err
	}
	current := post
	seen := map[string]bool{}
	for current.ParentID != nil {
		if seen[current.ID] {
			return nil, nil, fmt.Errorf("post ancestry cycle at %s", current.ID)
		}
		seen[current.ID] = true
		current, err = b.store.GetPost(ctx, *current.ParentID)
		if err != nil {
			return nil, nil, err
		}
	}
	return post, current, nil
}

func (b *Bot) notifyInboundReply(parent, root, reply *store.Post, author *store.User) {
	if parent == nil || root == nil || reply == nil || author == nil || b.mail == nil {
		return
	}
	if _, disabled := b.mail.(mail.Nop); disabled {
		return
	}
	recipientID := parent.AuthorID
	if author.Admin() {
		recipientID = root.AuthorID
	}
	if recipientID == author.ID {
		return
	}
	msg := mail.PostReply{
		RootID:          root.ID,
		RootTitle:       root.Title,
		ReplyID:         reply.ID,
		ReplyBody:       reply.Body,
		ReplyAuthorName: author.Name,
	}
	go func() {
		ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
		defer cancel()
		recipient, err := b.store.UserByID(ctx, recipientID)
		if err != nil {
			log.Printf("notify reply %s: load recipient: %v", msg.ReplyID, err)
			return
		}
		if recipient == nil || strings.TrimSpace(recipient.Email) == "" {
			return
		}
		msg.ToEmail = recipient.Email
		msg.ToName = recipient.Name
		if err := b.mail.NotifyPostReply(ctx, msg); err != nil {
			log.Printf("notify reply %s: %v", msg.ReplyID, err)
			return
		}
		log.Printf("notify reply %s: accepted", msg.ReplyID)
	}()
}