package security

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

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

	"github.com/bwmarrin/discordgo"
)

// usableQuarantineRole returns the configured quarantine role if it is safe
// to hand out right now: it exists, isn't @everyone or managed by an
// integration, and has none of the dangerous permissions. Checked at use, so
// a role that gained permissions since it was configured is never assigned.
func usableQuarantineRole(s *securityrepo.Settings, guildID string, roles []*discordgo.Role) string {
	if s.QuarantineRoleID == 0 || id(s.QuarantineRoleID) == guildID {
		return ""
	}
	for _, r := range roles {
		if r.ID == id(s.QuarantineRoleID) {
			if r.Managed || r.Permissions&DangerousPerms != 0 {
				return ""
			}
			return r.ID
		}
	}
	return ""
}

// Quarantine neutralises a member: every role it can remove is taken away
// (and saved, so it can be given back), the quarantine role is added if one
// is configured, and the member is timed out for the longest Discord allows.
// Bots are kicked instead, since their own integration role can't be
// removed. The owner and the bot itself are never touched.
func (e *Engine) Quarantine(ctx context.Context, guildID, userID, reason string) error {
	if userID == "" || userID == e.botID || e.IsOwner(guildID, userID) {
		return errors.New("refusing to quarantine the owner or the bot")
	}
	s, _, err := e.load(ctx, guildID)
	if err != nil {
		return err
	}
	m, err := e.d.GuildMember(guildID, userID)
	if err != nil {
		return fmt.Errorf("looking up the member: %w", err)
	}
	if m.User != nil && m.User.Bot {
		return e.d.GuildMemberDeleteWithReason(guildID, userID, clip("Velox anti-nuke: "+reason, 400))
	}
	roles, err := e.d.GuildRoles(guildID)
	if err != nil {
		return fmt.Errorf("listing roles: %w", err)
	}
	managed := map[string]bool{}
	for _, r := range roles {
		if r.Managed {
			managed[r.ID] = true
		}
	}

	var keep []string
	var previous []int64
	for _, r := range m.Roles {
		if managed[r] {
			keep = append(keep, r) // can't be removed (e.g. a Nitro booster role)
		} else {
			previous = append(previous, parseID(r))
		}
	}
	qRole := usableQuarantineRole(s, guildID, roles)
	withRole := keep
	if qRole != "" {
		withRole = append(append([]string(nil), keep...), qRole)
	}

	// Save first: if Discord fails half-way, the roles are still on record.
	if err := e.st.SaveQuarantine(ctx, securityrepo.Quarantine{
		GuildID: parseID(guildID), UserID: parseID(userID), PreviousRoleIDs: previous, Reason: clip(reason, 300),
	}); err != nil {
		return fmt.Errorf("saving the quarantine: %w", err)
	}

	audit := discordgo.WithAuditLogReason(clip("Velox anti-nuke: "+reason, 400))
	var errs []error
	if _, err := e.d.GuildMemberEdit(guildID, userID, &discordgo.GuildMemberParams{Roles: &withRole}, audit); err != nil {
		// A quarantine role Velox can't assign (e.g. moved above its own
		// role) must not stop the roles from being removed: retry without it.
		if qRole == "" {
			errs = append(errs, fmt.Errorf("removing roles: %w", err))
		} else if _, err2 := e.d.GuildMemberEdit(guildID, userID, &discordgo.GuildMemberParams{Roles: &keep}, audit); err2 != nil {
			errs = append(errs, fmt.Errorf("removing roles: %w", err2))
		} else {
			log.Printf("security: quarantine role %s couldn't be assigned in guild %s (%v); roles were still removed", qRole, guildID, err)
		}
	}
	until := e.now().Add(timeoutQuarantine)
	if err := e.d.GuildMemberTimeout(guildID, userID, &until, audit); err != nil {
		errs = append(errs, fmt.Errorf("timing out: %w", err))
	}
	e.event(ctx, guildID, securityrepo.EventQuarantined, e.botID, userID, reason)
	return errors.Join(errs...)
}

// Release undoes a quarantine: the saved roles that still exist are given
// back, the quarantine role and the timeout are removed. Releasing relaxes
// protection, so callers must check the actor first.
func (e *Engine) Release(ctx context.Context, guildID, userID, by string) error {
	rec, err := e.st.GetQuarantine(ctx, parseID(guildID), parseID(userID))
	if err != nil {
		return err
	}
	if rec == nil {
		return UserError("That member isn't quarantined.")
	}
	s, _, err := e.load(ctx, guildID)
	if err != nil {
		return err
	}
	m, err := e.d.GuildMember(guildID, userID)
	if err != nil {
		// They left: there's nothing to give back.
		if derr := e.st.DeleteQuarantine(ctx, parseID(guildID), parseID(userID)); derr != nil {
			return derr
		}
		e.event(ctx, guildID, securityrepo.EventReleased, by, userID, "member had left")
		return nil
	}
	roles, err := e.d.GuildRoles(guildID)
	if err != nil {
		return fmt.Errorf("listing roles: %w", err)
	}
	exists := map[string]bool{}
	for _, r := range roles {
		if !r.Managed && r.ID != guildID {
			exists[r.ID] = true
		}
	}
	qRole := ""
	if s.QuarantineRoleID != 0 {
		qRole = id(s.QuarantineRoleID)
	}

	seen := map[string]bool{}
	var next []string
	add := func(r string) {
		if !seen[r] && r != qRole {
			seen[r] = true
			next = append(next, r)
		}
	}
	for _, r := range m.Roles {
		add(r)
	}
	for _, r := range rec.PreviousRoleIDs {
		if exists[id(r)] {
			add(id(r))
		}
	}

	audit := discordgo.WithAuditLogReason("Velox security: quarantine released")
	if _, err := e.d.GuildMemberEdit(guildID, userID, &discordgo.GuildMemberParams{Roles: &next}, audit); err != nil {
		return fmt.Errorf("giving the roles back: %w", err)
	}
	if err := e.d.GuildMemberTimeout(guildID, userID, nil, audit); err != nil {
		log.Printf("security: removing the timeout of %s in guild %s: %v", userID, guildID, err)
	}
	if err := e.st.DeleteQuarantine(ctx, parseID(guildID), parseID(userID)); err != nil {
		return err
	}
	e.event(ctx, guildID, securityrepo.EventReleased, by, userID, fmt.Sprintf("%d roles given back", len(rec.PreviousRoleIDs)))
	e.send(ctx, guildID, s, alert{embed: &discordgo.MessageEmbed{
		Title:       "Quarantine released",
		Description: fmt.Sprintf("<@%s> was released by <@%s> and got their roles back.", userID, by),
		Color:       colorOK,
		Timestamp:   e.now().UTC().Format(time.RFC3339),
	}})
	return nil
}

// Quarantines lists who is quarantined in a guild.
// Events returns the server's recent security history, newest first.
func (e *Engine) Events(ctx context.Context, guildID string, limit int) ([]securityrepo.Event, error) {
	return e.st.ListEvents(ctx, parseID(guildID), limit)
}

func (e *Engine) Quarantines(ctx context.Context, guildID string) ([]securityrepo.Quarantine, error) {
	return e.st.ListQuarantines(ctx, parseID(guildID))
}