package security

import (
	"context"
	"errors"
	"fmt"
	"log"
	"strings"
	"sync"
	"time"

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

	"github.com/bwmarrin/discordgo"
)

// Memory bounds per server, so a huge raid can't exhaust the bot.
const (
	maxRecentJoins = 500
	maxCaught      = 20000
)

// CustomIDEndRaid is the alert's "End raid" button.
const CustomIDEndRaid = "security:endraid"

type joinRec struct {
	user    *discordgo.User
	at      time.Time
	handled bool // already removed by the join lock or Join Gate
}

type caughtRec struct {
	userID, name, action string
}

type raid struct {
	mu            sync.Mutex
	joins         []joinRec
	active        bool
	started       time.Time
	lastJoin      time.Time
	caught        []caughtRec
	caughtTotal   int
	pausedInvites bool
}

func (e *Engine) raidFor(guildID string) *raid {
	e.mu.Lock()
	defer e.mu.Unlock()
	r, ok := e.raids[guildID]
	if !ok {
		r = &raid{}
		e.raids[guildID] = r
	}
	return r
}

// RaidActive reports whether raid mode is on in a guild.
func (e *Engine) RaidActive(guildID string) bool {
	e.mu.Lock()
	r, ok := e.raids[guildID]
	e.mu.Unlock()
	if !ok {
		return false
	}
	r.mu.Lock()
	defer r.mu.Unlock()
	return r.active
}

// raidJoin records a join and, during a raid, acts on the raiders. It returns
// the action taken on this member ("" when none).
func (e *Engine) raidJoin(ctx context.Context, guildID string, s *securityrepo.Settings, m *discordgo.Member, handled bool) string {
	if !s.AntiRaidEnabled {
		return ""
	}
	now := e.now()
	window := time.Duration(s.RaidJoinSeconds) * time.Second
	r := e.raidFor(guildID)

	r.mu.Lock()
	r.joins = append(r.joins, joinRec{user: m.User, at: now, handled: handled})
	cut := 0
	for cut < len(r.joins) && now.Sub(r.joins[cut].at) > window {
		cut++
	}
	r.joins = r.joins[cut:]
	if len(r.joins) > maxRecentJoins {
		r.joins = r.joins[len(r.joins)-maxRecentJoins:]
	}
	r.lastJoin = now

	var targets []joinRec
	starting := false
	switch {
	case !r.active && len(r.joins) >= s.RaidJoinCount:
		// Raid starts: everyone in the burst that triggered it is a raider.
		starting = true
		r.active, r.started, r.caught, r.caughtTotal, r.pausedInvites = true, now, nil, 0, false
		targets = append(targets, r.joins...)
	case r.active:
		targets = []joinRec{{user: m.User, at: now, handled: handled}}
	}
	r.mu.Unlock()

	if starting {
		e.startRaid(ctx, guildID, s, len(targets))
	}

	action := s.RaidAction
	thisMember := ""
	for _, t := range targets {
		did := action
		if t.handled || action == securityrepo.ActionAlert {
			did = "flagged"
		} else if err := e.punish(guildID, t.user, action, "raid"); errors.Is(err, errProtected) {
			did = "skipped"
		} else if err != nil {
			log.Printf("security: raid action on %s in guild %s: %v", t.user.ID, guildID, err)
			did = "failed"
		}
		r.mu.Lock()
		r.caughtTotal++
		keep := len(r.caught) < maxCaught
		if keep {
			r.caught = append(r.caught, caughtRec{userID: t.user.ID, name: safeName(t.user), action: did})
		}
		r.mu.Unlock()
		if keep {
			if err := e.st.AddRaidCaught(ctx, parseID(guildID), securityrepo.Caught{UserID: parseID(t.user.ID), Action: did, Name: safeName(t.user)}); err != nil {
				log.Printf("security: recording raider %s in guild %s: %v", t.user.ID, guildID, err)
			}
		}
		if t.user.ID == m.User.ID && did == action {
			thisMember = action
		}
	}
	if len(targets) > 0 {
		e.persistRaid(ctx, guildID, r)
	}
	return thisMember
}

// persistRaid writes the raid's state so a restart can resume it.
func (e *Engine) persistRaid(ctx context.Context, guildID string, r *raid) {
	r.mu.Lock()
	x := securityrepo.Raid{GuildID: parseID(guildID), StartedAt: r.started, LastJoinAt: r.lastJoin, InvitesPaused: r.pausedInvites, CaughtTotal: r.caughtTotal}
	active := r.active
	r.mu.Unlock()
	if !active {
		return
	}
	if err := e.st.SaveRaid(ctx, x); err != nil {
		log.Printf("security: saving raid state for guild %s: %v", guildID, err)
	}
}

// ResumeRaids reloads raids that were in progress when the bot stopped, so
// raid mode stays on, its quiet timer keeps counting from the last join, and
// paused invites are resumed when it ends.
func (e *Engine) ResumeRaids(ctx context.Context) {
	raids, err := e.st.ListRaids(ctx)
	if err != nil {
		log.Printf("security: loading raids in progress: %v", err)
		return
	}
	for _, x := range raids {
		r := e.raidFor(id(x.GuildID))
		r.mu.Lock()
		r.active, r.started, r.lastJoin, r.pausedInvites, r.caughtTotal = true, x.StartedAt, x.LastJoinAt, x.InvitesPaused, x.CaughtTotal
		r.mu.Unlock()
	}
}

func (e *Engine) startRaid(ctx context.Context, guildID string, s *securityrepo.Settings, joins int) {
	e.event(ctx, guildID, securityrepo.EventRaidStarted, e.botID, "", fmt.Sprintf("%d joins in %ds", joins, s.RaidJoinSeconds))

	paused := false
	if s.RaidPauseInvites {
		if err := e.setInvitesPaused(guildID, true); err != nil {
			log.Printf("security: pausing invites in guild %s: %v", guildID, err)
		} else {
			paused = true
			r := e.raidFor(guildID)
			r.mu.Lock()
			r.pausedInvites = true
			r.mu.Unlock()
		}
	}

	e.persistRaid(ctx, guildID, e.raidFor(guildID))

	what := map[string]string{
		securityrepo.ActionAlert: "nobody is being removed (alert only)", securityrepo.ActionTimeout: "raiders are being timed out",
		securityrepo.ActionKick: "raiders are being kicked", securityrepo.ActionBan: "raiders are being banned",
	}[s.RaidAction]
	desc := fmt.Sprintf("%d members joined within %d seconds. Raid mode is on: %s.", joins, s.RaidJoinSeconds, what)
	if paused {
		desc += "\nInvites are paused until the raid ends."
	}
	desc += fmt.Sprintf("\nIt ends after %d minutes without a join, or with the button below (owner or trusted only).", s.RaidQuietMinutes)
	e.send(ctx, guildID, s, alert{
		ping: true, critical: true,
		embed: &discordgo.MessageEmbed{
			Title: "🚨 Raid detected", Description: desc, Color: colorAlert,
			Timestamp: e.now().UTC().Format(time.RFC3339),
		},
		components: []discordgo.MessageComponent{discordgo.ActionsRow{Components: []discordgo.MessageComponent{
			discordgo.Button{Label: "End raid", Style: discordgo.SecondaryButton, CustomID: CustomIDEndRaid},
		}}},
	})
}

// EndRaid turns raid mode off. by is who ended it ("" for the quiet timer).
// Ending a raid relaxes protection, so callers must check the actor first.
func (e *Engine) EndRaid(ctx context.Context, guildID, by string) error {
	e.mu.Lock()
	r, ok := e.raids[guildID]
	e.mu.Unlock()
	if !ok {
		return UserError("There's no raid going on.")
	}
	r.mu.Lock()
	if !r.active {
		r.mu.Unlock()
		return UserError("There's no raid going on.")
	}
	started, caught, total, paused := r.started, r.caught, r.caughtTotal, r.pausedInvites
	r.active, r.caught, r.caughtTotal, r.pausedInvites, r.joins = false, nil, 0, false, nil
	r.mu.Unlock()

	if paused {
		if err := e.setInvitesPaused(guildID, false); err != nil {
			log.Printf("security: resuming invites in guild %s: %v", guildID, err)
		}
	}

	how := "after a quiet period"
	if by != "" {
		how = "by <@" + by + ">"
	}
	e.event(ctx, guildID, securityrepo.EventRaidEnded, by, "", fmt.Sprintf("%d raiders caught", total))

	// The database has the full list even across a restart; memory is the
	// fallback if it can't be read.
	if saved, err := e.st.ListRaidCaught(ctx, parseID(guildID), maxCaught); err == nil && len(saved) >= len(caught) {
		caught = caught[:0]
		for _, c := range saved {
			caught = append(caught, caughtRec{userID: id(c.UserID), action: c.Action, name: c.Name})
		}
	}
	if err := e.st.DeleteRaid(ctx, parseID(guildID)); err != nil {
		log.Printf("security: clearing raid state for guild %s: %v", guildID, err)
	}

	var list strings.Builder
	fmt.Fprintf(&list, "Raid from %s to %s (UTC)\n\n", started.UTC().Format("2006-01-02 15:04:05"), e.now().UTC().Format("15:04:05"))
	for _, c := range caught {
		fmt.Fprintf(&list, "%s\t%s\t%s\n", c.userID, c.action, c.name)
	}
	if total > len(caught) {
		fmt.Fprintf(&list, "... and %d more\n", total-len(caught))
	}
	desc := fmt.Sprintf("Raid mode ended %s. %d accounts were caught; the list is attached.", how, total)
	if paused {
		desc += "\nInvites are open again."
	}
	if s, _, err := e.load(ctx, guildID); err == nil {
		e.send(ctx, guildID, s, alert{
			critical: true,
			embed:    &discordgo.MessageEmbed{Title: "Raid over", Description: desc, Color: colorOK},
			file:     textFile("raid-"+started.UTC().Format("20060102-1504")+".txt", list.String()),
		})
	}
	return nil
}

// WatchRaids ends raids after their quiet period and frees memory for
// servers that have gone quiet. It runs until ctx ends.
func (e *Engine) WatchRaids(ctx context.Context, every time.Duration) {
	t := time.NewTicker(every)
	defer t.Stop()
	for {
		select {
		case <-ctx.Done():
			return
		case <-t.C:
			e.checkRaids(ctx)
		}
	}
}

func (e *Engine) checkRaids(ctx context.Context) {
	e.mu.Lock()
	guilds := make([]string, 0, len(e.raids))
	for g := range e.raids {
		guilds = append(guilds, g)
	}
	e.mu.Unlock()

	now := e.now()
	for _, g := range guilds {
		s, _, err := e.load(ctx, g)
		if err != nil {
			continue
		}
		r := e.raidFor(g)
		r.mu.Lock()
		active, last := r.active, r.lastJoin
		r.mu.Unlock()
		switch {
		case active && now.Sub(last) >= time.Duration(s.RaidQuietMinutes)*time.Minute:
			_ = e.EndRaid(ctx, g, "")
		case !active && now.Sub(last) > 10*time.Minute:
			e.mu.Lock()
			delete(e.raids, g)
			e.mu.Unlock()
		}
	}
}

// setInvitesPaused uses Discord's built-in "pause invites" (guild incident
// actions). Paused for up to 24 hours, Discord's maximum; resumed when the
// raid ends.
func (e *Engine) setInvitesPaused(guildID string, paused bool) error {
	body := map[string]any{"invites_disabled_until": nil}
	if paused {
		body["invites_disabled_until"] = e.now().Add(24 * time.Hour).UTC().Format(time.RFC3339)
	}
	url := discordgo.EndpointGuild(guildID) + "/incident-actions"
	_, err := e.d.RequestWithBucketID("PUT", url, body, url)
	return err
}