package game

import (
	"crypto/rand"
	"encoding/hex"
	"fmt"
	"log"
	"os"
	"path/filepath"
	"strings"

	"thehouseoficarus/internal/net"
	"thehouseoficarus/internal/persistence"
	"thehouseoficarus/internal/player"
)

// Account/character lifecycle operations. Each is one journal transaction
// over the affected files (account list, character files), executed with the
// game's single-owner guarantee: the online check, file mutation, registry
// update, and cross-session refresh happen without any interleaved session
// input, closing the check-then-rename gap. Save/remove errors are
// propagated to the caller, never ignored.
//
// All handlers here are invoked from session input (already on the owner).

// journalDir is the persistence journal directory under the game data dir.
func (g *Game) journalDir() string {
	return filepath.Join(g.DataDir, ".journal")
}

// newTxn starts a lifecycle transaction.
func (g *Game) newTxn() *persistence.Transaction {
	return persistence.NewTransaction(g.journalDir())
}

// adoptCharacterIdentity backfills stable identity fields on a loaded
// character: a UUID (assigned once at first load and persisted) and the
// owning account name. Legacy characters without these fields get them at
// first connection and are re-saved so subsequent authorizations can use
// them. Called from the owner goroutine only.
func (g *Game) adoptCharacterIdentity(p *player.Player, accountName string) {
	if p.ID == "" {
		p.ID = newCharacterID()
	}
	if p.Account == "" {
		p.Account = accountName
	}
	if err := g.AccountStore.SaveCharacter(p); err != nil {
		// Identity backfill is best-effort: the character remains usable,
		// but membership validation falls back to the account list.
		log.Printf("identity backfill for %s: %v", p.Name, err)
	}
}

// newCharacterID returns a random UUID (v4, formatted without dashes is
// unnecessary; standard hyphenated form is used).
func newCharacterID() string {
	var b [16]byte
	if _, err := rand.Read(b[:]); err != nil {
		panic(fmt.Sprintf("character id generation: %v", err))
	}
	b[6] = (b[6] & 0x0f) | 0x40 // version 4
	b[8] = (b[8] & 0x3f) | 0x80 // RFC 4122 variant
	s := hex.EncodeToString(b[:])
	return s[0:8] + "-" + s[8:12] + "-" + s[12:16] + "-" + s[16:20] + "-" + s[20:32]
}

// backfillCharacterIDs migrates every character file at startup: assigns
// missing IDs and owner fields (owner derived from account character lists
// for legacy files) and persists them.
func (g *Game) backfillCharacterIDs() {
	names, err := g.AccountStore.ListCharacterNames()
	if err != nil {
		return
	}
	owners := map[string]string{} // character (lower) -> owning account
	accounts, _ := g.AccountStore.ListAccountNames()
	for _, accName := range accounts {
		acc, err := g.AccountStore.LoadAccount(accName)
		if err != nil {
			continue
		}
		for _, c := range acc.Characters {
			owners[strings.ToLower(c)] = acc.Name
		}
	}
	for _, name := range names {
		p, err := g.AccountStore.LoadCharacter(name)
		if err != nil {
			log.Printf("character migration load %s: %v", name, err)
			continue
		}
		changed := false
		if p.ID == "" {
			p.ID = newCharacterID()
			changed = true
		}
		if p.Account == "" {
			if owner, ok := owners[strings.ToLower(p.Name)]; ok {
				p.Account = owner
				changed = true
			}
		}
		if changed {
			if err := g.AccountStore.SaveCharacter(p); err != nil {
				log.Printf("character migration save %s: %v", p.Name, err)
			}
		}
	}
}

// canonicAccount returns the account name in its canonical on-disk form.
func (g *Game) canonicalAccount(name string) (string, error) {
	return g.AccountStore.FindAccount(name)
}

// canonicChar returns the character name in its canonical on-disk form.
func (g *Game) canonicalChar(name string) (string, error) {
	return g.AccountStore.FindCharacter(name)
}

// createCharacterTxn creates the character file and appends it to the
// owning account in a single transaction. Returns the created player.
func (g *Game) createCharacterTxn(accountName, charName string, startingRoom int) (*player.Player, error) {
	p := player.New(charName)
	p.RoomID = startingRoom
	p.Stats.RecordRoomVisit(startingRoom)
	p.ID = newCharacterID()
	p.Account = accountName
	data, err := g.AccountStore.MarshalCharacter(p)
	if err != nil {
		return nil, err
	}
	txn := g.newTxn()
	if err := txn.Replace(g.AccountStore.CharPath(charName), data, 0600); err != nil {
		return nil, err
	}
	acc, err := g.AccountStore.LoadAccount(accountName)
	if err != nil {
		return nil, err
	}
	acc.Characters = append(acc.Characters, charName)
	accData, err := g.AccountStore.MarshalAccount(acc)
	if err != nil {
		return nil, err
	}
	if err := txn.Replace(g.AccountStore.AccountPath(accountName), accData, 0600); err != nil {
		return nil, err
	}
	return p, txn.Commit()
}

// renameCharacterTxn atomically renames the character file, persists the new
// name inside it, and updates the owning account's character list.
func (g *Game) renameCharacterTxn(accountName, oldName, newName string) error {
	txn := g.newTxn()
	if err := txn.Move(g.AccountStore.CharPath(oldName), g.AccountStore.CharPath(newName)); err != nil {
		return err
	}
	p, err := g.AccountStore.LoadCharacter(oldName)
	if err != nil {
		return err
	}
	p.Name = newName
	data, err := g.AccountStore.MarshalCharacter(p)
	if err != nil {
		return err
	}
	if err := txn.Replace(g.AccountStore.CharPath(newName), data, 0600); err != nil {
		return err
	}
	acc, err := g.AccountStore.LoadAccount(accountName)
	if err != nil {
		return err
	}
	chars := make([]string, 0, len(acc.Characters))
	for _, c := range acc.Characters {
		if c == oldName {
			chars = append(chars, newName)
		} else {
			chars = append(chars, c)
		}
	}
	acc.Characters = chars
	accData, err := g.AccountStore.MarshalAccount(acc)
	if err != nil {
		return err
	}
	if err := txn.Replace(g.AccountStore.AccountPath(accountName), accData, 0600); err != nil {
		return err
	}
	return txn.Commit()
}

// deleteCharacterTxn removes the character file and updates the account list
// atomically.
func (g *Game) deleteCharacterTxn(accountName, charName string) error {
	txn := g.newTxn()
	if err := txn.Delete(g.AccountStore.CharPath(charName)); err != nil {
		return err
	}
	acc, err := g.AccountStore.LoadAccount(accountName)
	if err != nil {
		return err
	}
	var chars []string
	for _, c := range acc.Characters {
		if c != charName {
			chars = append(chars, c)
		}
	}
	acc.Characters = chars
	accData, err := g.AccountStore.MarshalAccount(acc)
	if err != nil {
		return err
	}
	if err := txn.Replace(g.AccountStore.AccountPath(accountName), accData, 0600); err != nil {
		return err
	}
	return txn.Commit()
}

// purgeAccountTxn removes the account file and every character file in one
// transaction.
func (g *Game) purgeAccountTxn(accountName string, characters []string) error {
	txn := g.newTxn()
	for _, name := range characters {
		if err := txn.Delete(g.AccountStore.CharPath(name)); err != nil {
			return err
		}
	}
	if err := txn.Delete(g.AccountStore.AccountPath(accountName)); err != nil {
		return err
	}
	return txn.Commit()
}

// renameAccountTxn moves the account file and rewrites its embedded name in
// one transaction.
func (g *Game) renameAccountTxn(oldName, newName string) error {
	txn := g.newTxn()
	if err := txn.Move(g.AccountStore.AccountPath(oldName), g.AccountStore.AccountPath(newName)); err != nil {
		return err
	}
	acc, err := g.AccountStore.LoadAccount(oldName)
	if err != nil {
		return err
	}
	acc.Name = newName
	accData, err := g.AccountStore.MarshalAccount(acc)
	if err != nil {
		return err
	}
	if err := txn.Replace(g.AccountStore.AccountPath(newName), accData, 0600); err != nil {
		return err
	}
	return txn.Commit()
}

// isMemberOf reports whether characterName belongs to accountName by
// checking the character file's owner field (falling back to the account's
// character list for legacy files), case-insensitively.
func (g *Game) isMemberOf(accountName, characterName string) bool {
	p, err := g.AccountStore.LoadCharacter(characterName)
	if err != nil {
		return false
	}
	if p.Account != "" {
		return equalsFold(p.Account, accountName)
	}
	acc, err := g.AccountStore.LoadAccount(accountName)
	if err != nil {
		return false
	}
	for _, c := range acc.Characters {
		if equalsFold(c, characterName) {
			return true
		}
	}
	return false
}

// publishAccountUpdate reloads the account from disk and republishes its
// state to every session of that account, resetting stale pending menu
// selections (pending character names, menu choices) after lifecycle
// mutations. Called from the owner goroutine only.
func (g *Game) publishAccountUpdate(accountName string) {
	for _, sess := range g.allSessionsOfAccount(accountName) {
		acc, err := g.AccountStore.LoadAccount(accountName)
		if err != nil {
			// The account file vanished (purge from another session); the
			// session is stale and must leave the menu.
			sess.Account = nil
			sess.PendingChar = ""
			sess.PendingMenu = nil
			sess.WriteLine("\nYour account no longer exists.")
			sess.Close()
			continue
		}
		sess.Account = &player.Account{
			Name:         acc.Name,
			PasswordHash: acc.PasswordHash,
			Characters:   acc.Characters,
			Aliases:      acc.Aliases,
			Colors:       acc.Colors,
			Options:      acc.Options,
			Admin:        acc.Admin,
		}
		if sess.Account.Aliases == nil {
			sess.Account.Aliases = make(map[string]string)
		}
		if sess.Account.Colors == nil {
			sess.Account.Colors = make(map[string]string)
		}
		if sess.Account.Options == nil {
			sess.Account.Options = make(map[string]any)
		}
		// Any pending selection referencing a deleted/renamed character is
		// stale now; revalidate before reuse.
		sess.PendingMenu = nil
		if sess.PendingChar != "" && sess.PendingChar != "connect" {
			found := false
			for _, c := range sess.Account.Characters {
				if equalsFold(c, sess.PendingChar) {
					found = true
					break
				}
			}
			if !found {
				sess.PendingChar = ""
				sess.State = net.StateMenu
				g.showMenu(sess)
			}
		}
	}
}

// allSessionsOfAccount returns every session authenticated to accountName,
// including sessions sitting in menus (not just in-game characters).
func (g *Game) allSessionsOfAccount(accountName string) []*net.Session {
	if g.Hub == nil {
		return nil
	}
	var out []*net.Session
	for _, sess := range g.Hub.AllSessions() {
		if sess.Account != nil && equalsFold(sess.Account.Name, accountName) {
			out = append(out, sess)
		}
	}
	return out
}

// equalsFold is a small case-insensitive string equality helper.
func equalsFold(a, b string) bool {
	if len(a) != len(b) {
		return false
	}
	for i := 0; i < len(a); i++ {
		ca, cb := a[i], b[i]
		if 'A' <= ca && ca <= 'Z' {
			ca += 'a' - 'A'
		}
		if 'A' <= cb && cb <= 'Z' {
			cb += 'a' - 'A'
		}
		if ca != cb {
			return false
		}
	}
	return true
}

// recoverJournals rolls back leftover lifecycle journals at startup and
// surfaces unrecoverable ones.
func (g *Game) recoverJournals() {
	if err := persistence.Recover(g.journalDir()); err != nil {
		fmt.Fprintf(os.Stderr, "lifecycle journal recovery failed: %v\n", err)
		os.Exit(1)
	}
}