package game

// The economy journal: durable, idempotent money movement. Every casino
// wager and payout writes a journal record BEFORE the balance mutation,
// then the character save makes the balance durable, then the record is
// settled. A crash at any point leaves either:
//   - an open record with the character file at its pre-transaction state
//     (crash before save) — recovery settles it as void (debit) or applies
//     it (payout, which the player is owed); or
//   - an open record with the character file at its post-transaction state
//     (crash after save) — recovery refunds open debit records (the round
//     state was lost in the crash, so the stake returns) and voids payout
//     records that are already durable.
//
// The reducer folds journal lines by record ID (later lines win), so
// settlement markers are idempotent appends. Recovery runs once at startup
// before any session can join; compaction rewrites the journal keeping only
// open records (normally none).

import (
	"bufio"
	"crypto/rand"
	"encoding/hex"
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"time"

	"thehouseoficarus/internal/player"
)

type economyRecord struct {
	ID     string    `json:"id"`
	Player string    `json:"player"`
	Kind   string    `json:"kind"` // "wager" or "payout"
	Chips  int       `json:"chips"`
	Credit int       `json:"credits"`
	Status string    `json:"status"` // "open", "settled", "void"
	TS     time.Time `json:"ts"`

	// Balance checkpoints used to decide recovery compensation.
	CreditsBefore int `json:"credits_before"`
	CreditsAfter  int `json:"credits_after"`
	ChipsBefore   int `json:"chips_before"`
	ChipsAfter    int `json:"chips_after"`
}

type economyJournal struct {
	path string
}

func newEconomyJournal(dataDir string) *economyJournal {
	dir := filepath.Join(dataDir, "economy")
	_ = os.MkdirAll(dir, 0700)
	return &economyJournal{path: filepath.Join(dir, "journal.jsonl")}
}

func newEconomyRecordID() string {
	var b [8]byte
	if _, err := rand.Read(b[:]); err != nil {
		panic(fmt.Sprintf("economy record id: %v", err))
	}
	return hex.EncodeToString(b[:])
}

// append writes one durable line. Errors are returned to the caller, which
// must treat the transaction as failed.
func (j *economyJournal) append(rec economyRecord) error {
	rec.TS = time.Now()
	data, err := json.Marshal(rec)
	if err != nil {
		return err
	}
	f, err := os.OpenFile(j.path, os.O_CREATE|os.O_WRONLY|os.O_APPEND, 0600)
	if err != nil {
		return fmt.Errorf("open economy journal: %w", err)
	}
	defer f.Close()
	if _, err := f.Write(append(data, '\n')); err != nil {
		return fmt.Errorf("append economy journal: %w", err)
	}
	if err := f.Sync(); err != nil {
		return fmt.Errorf("sync economy journal: %w", err)
	}
	return nil
}

// start opens a durable record for the in-flight transaction.
func (j *economyJournal) start(kind string, p *player.Player, chips, credits, creditsBefore, creditsAfter, chipsBefore, chipsAfter int) (*economyRecord, error) {
	rec := &economyRecord{
		ID:            newEconomyRecordID(),
		Player:        p.Name,
		Kind:          kind,
		Chips:         chips,
		Credit:        credits,
		Status:        "open",
		CreditsBefore: creditsBefore,
		CreditsAfter:  creditsAfter,
		ChipsBefore:   chipsBefore,
		ChipsAfter:    chipsAfter,
	}
	if err := j.append(*rec); err != nil {
		return nil, err
	}
	return rec, nil
}

// settle marks a record settled (the balance mutation is durable).
func (j *economyJournal) settle(rec *economyRecord) {
	rec.Status = "settled"
	_ = j.append(*rec)
}

// void marks a record void (the mutation was reverted in memory and never
// became durable; recovery must not compensate).
func (j *economyJournal) void(rec *economyRecord) {
	rec.Status = "void"
	_ = j.append(*rec)
}

// loadOpen folds the journal and returns the still-open records.
func (j *economyJournal) loadOpen() []*economyRecord {
	f, err := os.Open(j.path)
	if err != nil {
		return nil
	}
	defer f.Close()
	latest := map[string]*economyRecord{}
	scanner := bufio.NewScanner(f)
	scanner.Buffer(make([]byte, 0, 64*1024), 1024*1024)
	for scanner.Scan() {
		line := scanner.Bytes()
		if len(line) == 0 {
			continue
		}
		var rec economyRecord
		if err := json.Unmarshal(line, &rec); err != nil {
			// A torn final line (crash mid-append) is not a valid record;
			// skip it. Appends are small and single-line, so only the last
			// line can be torn.
			continue
		}
		latest[rec.ID] = &rec
	}
	var open []*economyRecord
	for _, rec := range latest {
		if rec.Status == "open" {
			open = append(open, rec)
		}
	}
	return open
}

// compact rewrites the journal keeping only still-open records.
func (j *economyJournal) compact() {
	open := j.loadOpen()
	tmp := j.path + ".compact"
	f, err := os.OpenFile(tmp, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0600)
	if err != nil {
		return
	}
	defer os.Remove(tmp)
	w := bufio.NewWriter(f)
	for _, rec := range open {
		rec.TS = time.Now()
		data, err := json.Marshal(rec)
		if err != nil {
			continue
		}
		w.Write(data)
		w.WriteByte('\n')
	}
	if err := w.Flush(); err != nil {
		f.Close()
		return
	}
	if err := f.Sync(); err != nil {
		f.Close()
		return
	}
	f.Close()
	// Best-effort atomic-ish replacement; a torn compaction leaves the
	// original file intact.
	if err := os.Rename(tmp, j.path); err != nil {
		os.Remove(tmp)
	}
}

// giveChips re-credits chips to a player's inventory (used by recovery
// refunds). Stacks onto an existing chips slot when one exists.
func (g *Game) giveChips(p *player.Player, qty int) {
	for _, slot := range p.Inventory {
		if slot != nil && slot.ItemID == "chips" {
			slot.Quantity += qty
			return
		}
	}
	slot := p.FirstFreeSlot()
	if slot >= 0 {
		p.SetInvSlot(slot, &player.InventorySlot{ItemID: "chips", Quantity: qty})
	}
}

// payCreditsDurable applies a checked credit increase and persists it.
func (g *Game) payCreditsDurable(p *player.Player, amount int) error {
	if amount < 0 {
		return fmt.Errorf("negative payout %d", amount)
	}
	sum, err := addCreditsChecked(p.Credits, amount)
	if err != nil {
		return err
	}
	p.Credits = sum
	return g.AccountStore.SaveCharacter(p)
}

// addCreditsChecked is the game-side checked addition against the economy
// cap (mirrors casino.MaxCredits; kept local to avoid a dependency cycle).
func addCreditsChecked(a, b int) (int, error) {
	const maxCredits = 1_000_000_000_000
	if b > 0 && a > maxCredits-b {
		return maxCredits, fmt.Errorf("credit overflow: %d + %d exceeds %d", a, b, maxCredits)
	}
	if b < 0 {
		return 0, fmt.Errorf("negative credit add %d", b)
	}
	return a + b, nil
}

// recoverEconomy compensates open records from the last crash. It is called
// once from New, before any session connects.
func (g *Game) recoverEconomy() {
	if g.Economy == nil {
		return
	}
	records := g.Economy.loadOpen()
	compensated := 0
	for _, rec := range records {
		p, err := g.AccountStore.LoadCharacter(rec.Player)
		if err != nil {
			// Character file unreadable: leave the record open so a later
			// attempt (or operator inspection) can resolve it; do not
			// silently drop money.
			fmt.Fprintf(os.Stderr, "economy recovery: load %s: %v\n", rec.Player, err)
			continue
		}
		switch {
		case rec.Kind == "wager" && p.Credits == rec.CreditsBefore:
			// The debit never became durable: void it.
			g.Economy.void(rec)
		case rec.Kind == "wager" && p.Credits == rec.CreditsAfter:
			// The debit is durable but the round was lost in the crash:
			// refund the stake (approved refund-on-recovery policy).
			chips, credits := rec.Chips, rec.Credit
			p.Credits += credits
			if chips > 0 {
				g.giveChips(p, chips)
			}
			if err := g.AccountStore.SaveCharacter(p); err != nil {
				fmt.Fprintf(os.Stderr, "economy recovery: refund save %s: %v\n", p.Name, err)
				continue
			}
			g.Economy.settle(rec)
			compensated++
		case rec.Kind == "wager":
			// Balance moved past the recorded checkpoint: cannot compensate
			// reliably; surface for operator inspection.
			fmt.Fprintf(os.Stderr, "economy recovery: ambiguous wager %s for %s (credits %d, want before %d or after %d)\n",
				rec.ID, rec.Player, p.Credits, rec.CreditsBefore, rec.CreditsAfter)
			g.Economy.void(rec)
		case rec.Kind == "payout" && p.Credits == rec.CreditsBefore:
			// The payout was lost in the crash: the player is owed it.
			if err := g.payCreditsDurable(p, rec.Credit); err != nil {
				fmt.Fprintf(os.Stderr, "economy recovery: payout save %s: %v\n", p.Name, err)
				continue
			}
			g.Economy.settle(rec)
			compensated++
		case rec.Kind == "payout" && p.Credits == rec.CreditsAfter:
			g.Economy.settle(rec)
		case rec.Kind == "payout":
			fmt.Fprintf(os.Stderr, "economy recovery: ambiguous payout %s for %s (credits %d, want before %d or after %d)\n",
				rec.ID, rec.Player, p.Credits, rec.CreditsBefore, rec.CreditsAfter)
			g.Economy.settle(rec)
		}
	}
	g.Economy.compact()
}