package security

import (
	"context"
	"fmt"
	"sort"
	"strings"
	"unicode"
	"unicode/utf8"

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

	"github.com/bwmarrin/discordgo"
)

// Tuning the thresholds, filters and actions. Everything the Join Gate, raid
// mode, anti-nuke and heat do can be adjusted from Discord with these calls;
// a dashboard is never needed. They follow the same rules as the rest of the
// configuration: the server owner or someone on the trusted list, checked
// here and not left to Discord's command permissions.

const (
	maxWords      = 50 // blocked words per list
	maxWordLength = 50
)

var (
	filterActions = map[string]bool{securityrepo.ActionOff: true, securityrepo.ActionTimeout: true, securityrepo.ActionKick: true, securityrepo.ActionBan: true}
	botActions    = map[string]bool{securityrepo.ActionOff: true, securityrepo.ActionKick: true, securityrepo.ActionBan: true}
	raidActions   = map[string]bool{securityrepo.ActionAlert: true, securityrepo.ActionTimeout: true, securityrepo.ActionKick: true, securityrepo.ActionBan: true}
	heatActions   = map[string]bool{securityrepo.ActionTimeout: true, securityrepo.ActionKick: true, securityrepo.ActionBan: true}
	strictnessSet = map[string]bool{"low": true, "medium": true, "high": true}
	nukeLimitKeys = map[string]bool{
		securityrepo.LimitChannelDelete: true, securityrepo.LimitChannelCreate: true, securityrepo.LimitRoleDelete: true,
		securityrepo.LimitRoleCreate: true, securityrepo.LimitBan: true, securityrepo.LimitKick: true, securityrepo.LimitWebhookCreate: true,
	}
)

// CleanWords trims, lowercases and de-duplicates a list of blocked words and
// rejects anything oversized or containing control characters. They are
// matched as plain text, never as regular expressions.
func CleanWords(in []string) ([]string, error) {
	seen := map[string]bool{}
	out := []string{}
	for _, w := range in {
		w = strings.ToLower(strings.TrimSpace(w))
		if w == "" || seen[w] {
			continue
		}
		if utf8.RuneCountInString(w) > maxWordLength {
			return nil, UserError("Each blocked word can be at most 50 characters.")
		}
		for _, r := range w {
			if unicode.IsControl(r) {
				return nil, UserError("Blocked words can't contain control characters.")
			}
		}
		seen[w] = true
		out = append(out, w)
	}
	if len(out) > maxWords {
		return nil, UserError("You can block at most 50 words.")
	}
	sort.Strings(out)
	return out, nil
}

func inRange(v *int, lo, hi int) bool { return v == nil || (*v >= lo && *v <= hi) }

func oneOf(v *string, allowed map[string]bool) bool { return v == nil || allowed[*v] }

// ValidateTuning returns a message for the first invalid field, or "". It
// also cleans the word lists in place.
func ValidateTuning(t *securityrepo.Tuning) error {
	for name, v := range map[string]*string{
		"No avatar": t.NoAvatar, "New account": t.NewAccount, "Invite in name": t.AdvertisingName, "Blocked words": t.UsernameFilter,
	} {
		if !oneOf(v, filterActions) {
			return UserError(name + " can be off, timeout, kick or ban.")
		}
	}
	if !oneOf(t.UnverifiedBot, botActions) || !oneOf(t.UnauthorizedBot, botActions) {
		return UserError("Bot filters can only be off, kick or ban.")
	}
	if !oneOf(t.RaidAction, raidActions) {
		return UserError("The raid action can be alert, timeout, kick or ban.")
	}
	if !oneOf(t.HeatStrictness, strictnessSet) {
		return UserError("Heat strictness must be low, medium or high.")
	}
	if !oneOf(t.HeatAction, heatActions) {
		return UserError("The heat action can be timeout, kick or ban.")
	}
	switch {
	case !inRange(t.MinAccountAgeDays, 1, 365):
		return UserError("Minimum account age must be between 1 and 365 days.")
	case !inRange(t.RaidJoinCount, 3, 100):
		return UserError("The raid join count must be between 3 and 100.")
	case !inRange(t.RaidJoinSeconds, 5, 300):
		return UserError("The raid window must be between 5 and 300 seconds.")
	case !inRange(t.RaidQuietMinutes, 1, 120):
		return UserError("The raid quiet period must be between 1 and 120 minutes.")
	case !inRange(t.AntiNukeWindowSeconds, 5, 300):
		return UserError("The anti-nuke window must be between 5 and 300 seconds.")
	case !inRange(t.HeatTimeoutMinutes, 1, 10080):
		return UserError("The heat timeout must be between 1 minute and 7 days (10080 minutes).")
	case !inRange(t.HeatPanicMembers, 0, 50):
		return UserError("Heat panic must be between 0 (off) and 50 members.")
	case t.HeatLockdownMentions != nil && *t.HeatLockdownMentions != 0 && (*t.HeatLockdownMentions < 5 || *t.HeatLockdownMentions > 1000):
		return UserError("The mention flood lockdown must be 0 (off) or between 5 and 1000 mentions.")
	}
	for k, v := range t.AntiNukeLimits {
		if !nukeLimitKeys[k] {
			return UserError("Unknown anti-nuke limit " + fmt.Sprintf("%q", k) + ".")
		}
		if v < 0 || v > 100 {
			return UserError("Anti-nuke limits must be between 0 and 100 (0 means never allowed).")
		}
	}
	if t.UsernamePatterns != nil {
		words, err := CleanWords(*t.UsernamePatterns)
		if err != nil {
			return err
		}
		t.UsernamePatterns = &words
	}
	if t.HeatBlockedWords != nil {
		words, err := CleanWords(*t.HeatBlockedWords)
		if err != nil {
			return err
		}
		t.HeatBlockedWords = &words
	}
	return nil
}

// Tune changes thresholds, filters and actions. Only the server owner or
// someone on the trusted list may.
func (e *Engine) Tune(ctx context.Context, guildID string, actor *discordgo.Member, t securityrepo.Tuning, summary string) error {
	if err := e.RequireTrusted(ctx, guildID, actor); err != nil {
		return err
	}
	if err := ValidateTuning(&t); err != nil {
		return err
	}
	if err := e.st.UpdateTuning(ctx, parseID(guildID), t); err != nil {
		return err
	}
	e.Invalidate(guildID)
	e.event(ctx, guildID, "settings", actor.User.ID, "", summary)
	return nil
}

// WordList names one of the two blocked word lists.
type WordList string

const (
	UsernameWords WordList = "username" // checked against new members' names by the Join Gate
	ChatWords     WordList = "chat"     // checked against messages by heat
)

// EditWords adds or removes one blocked word and returns the list as saved.
func (e *Engine) EditWords(ctx context.Context, guildID string, actor *discordgo.Member, list WordList, add bool, word string) ([]string, error) {
	if err := e.RequireTrusted(ctx, guildID, actor); err != nil {
		return nil, err
	}
	e.Invalidate(guildID) // read what is saved now, not what was cached
	cur, _, err := e.load(ctx, guildID)
	if err != nil {
		return nil, err
	}
	var words []string
	switch list {
	case UsernameWords:
		words = append(words, cur.UsernamePatterns...)
	case ChatWords:
		words = append(words, cur.HeatBlockedWords...)
	default:
		return nil, UserError("Unknown list.")
	}
	word = strings.ToLower(strings.TrimSpace(word))
	if word == "" {
		return nil, UserError("Give a word to block.")
	}
	if add {
		words = append(words, word)
	} else {
		kept := words[:0]
		for _, w := range words {
			if w != word {
				kept = append(kept, w)
			}
		}
		if len(kept) == len(words) {
			return nil, UserError("That word isn't on the list.")
		}
		words = kept
	}
	clean, err := CleanWords(words)
	if err != nil {
		return nil, err
	}
	t := securityrepo.Tuning{}
	if list == UsernameWords {
		t.UsernamePatterns = &clean
	} else {
		t.HeatBlockedWords = &clean
	}
	verb := "removed"
	if add {
		verb = "added"
	}
	if err := e.Tune(ctx, guildID, actor, t, fmt.Sprintf("%s word list: %s %q", list, verb, word)); err != nil {
		return nil, err
	}
	return clean, nil
}