package game

import (
	"encoding/json"
	"fmt"
	"os"
	"strings"
)

// A debug report is a snapshot of a game that went wrong, complete enough to
// reproduce it: the full authoritative state (every deck card by card, the shop
// row and remaining decks, discards, pending choices, per-player banks), every
// battle fought that round with its lineups and its recording of every die, and
// the entire event log.
//
// It exists in two forms. The JSON form is exact — feed it back through
// ParseDebugReport and you have the same Game the server had, ready to replay.
// The text form is for reading: the same content laid out for a human trying to
// work out which effect misfired. Report.Text() ends with a paste-ready test.
//
// Both forms contain hidden information — opponents' decks, the order of the
// shop decks — and that is an accepted trade: the in-game "Report a bug" button
// hands a player their own report on any server, DEBUG or not, because a bug
// nobody can reproduce costs more than the little a cheat would gain.
// `go run ./cmd/report` reads the same report out of the database.

// DebugReportVersion is the report format's version, so an old report found on
// disk can be recognized for what it is.
const DebugReportVersion = 1

// DebugReport is a captured game, ready to read or replay.
type DebugReport struct {
	Version int `json:"version"`
	// CapturedAt is an RFC3339 timestamp stamped by whoever took the report;
	// the engine is clockless and leaves it empty. Note is free text — what
	// looked wrong, in the reporter's words.
	CapturedAt string `json:"capturedAt,omitempty"`
	Note       string `json:"note,omitempty"`
	// Summary is the at-a-glance header, so a pile of reports can be triaged
	// (and filenames built) without unmarshalling the state.
	Summary DebugSummary `json:"summary"`
	// State is the complete Game, byte for byte as the server persists it.
	// Everything the report can tell you is derived from this.
	State json.RawMessage `json:"state"`
}

// DebugSummary identifies a report at a glance.
type DebugSummary struct {
	GameID     string   `json:"gameId"`
	Code       string   `json:"code"`
	Packs      []string `json:"packs"`
	Phase      Phase    `json:"phase"`
	Round      int      `json:"round"`
	Seats      []string `json:"seats"`          // display names, by seat
	Battles    int      `json:"battles"`        // battles recorded in this round
	LogEntries int      `json:"logEntries"`     // size of the event log
	WinnerSeat int      `json:"winnerSeat"`     // at gameover; -1 otherwise
	Bots       []int    `json:"bots,omitempty"` // seats played by the computer
}

// DebugReport captures the game as it stands. The caller owns the game lock;
// the report is a copy and shares nothing with it afterwards.
func (g *Game) DebugReport() (*DebugReport, error) {
	state, err := json.Marshal(g)
	if err != nil {
		return nil, fmt.Errorf("capture game state: %w", err)
	}
	sum := DebugSummary{
		GameID:     g.ID,
		Code:       g.Code,
		Packs:      g.packList(),
		Phase:      g.Phase,
		Round:      g.Round,
		Battles:    len(g.Battles),
		LogEntries: len(g.Log),
		WinnerSeat: g.WinnerSeat,
	}
	for _, p := range g.Players {
		sum.Seats = append(sum.Seats, p.Name)
		if p.IsBot {
			sum.Bots = append(sum.Bots, p.Seat)
		}
	}
	return &DebugReport{Version: DebugReportVersion, Summary: sum, State: state}, nil
}

// ParseDebugReport reads a report. It also accepts a bare game state — the raw
// JSON blob out of the store, or the `state` field pulled from a report — so
// anything game-shaped you can lay hands on can be replayed.
func ParseDebugReport(data []byte) (*DebugReport, error) {
	var r DebugReport
	if err := json.Unmarshal(data, &r); err != nil {
		return nil, fmt.Errorf("parse debug report: %w", err)
	}
	if len(r.State) == 0 {
		// Not a report — assume it's a game state and wrap it in one.
		var g Game
		if err := json.Unmarshal(data, &g); err != nil {
			return nil, fmt.Errorf("parse debug report: not a report or a game state: %w", err)
		}
		if g.ID == "" && g.Code == "" && len(g.Players) == 0 {
			return nil, fmt.Errorf("parse debug report: no game state found")
		}
		return g.DebugReport()
	}
	if _, err := r.Game(); err != nil {
		return nil, err
	}
	return &r, nil
}

// LoadDebugReportFile reads a report (or a bare game state) off disk. This is
// the entry point for a test built around a report: keep the JSON in testdata
// and load it here.
func LoadDebugReportFile(path string) (*DebugReport, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}
	return ParseDebugReport(data)
}

// Game rebuilds the captured game. Each call returns a fresh copy, so callers
// are free to poke at it — replay a battle, take another action, run the state
// forward — without disturbing the report or each other.
func (r *DebugReport) Game() (*Game, error) {
	var g Game
	if err := json.Unmarshal(r.State, &g); err != nil {
		return nil, fmt.Errorf("restore game state: %w", err)
	}
	return &g, nil
}

// JSON renders the report as indented JSON: what you save to a file, attach to
// a bug, or drop into testdata.
func (r *DebugReport) JSON() ([]byte, error) {
	return json.MarshalIndent(r, "", "  ")
}

// Filename is a descriptive, filesystem-safe name for this report.
func (r *DebugReport) Filename() string {
	code := r.Summary.Code
	if code == "" {
		code = "game"
	}
	return fmt.Sprintf("sap-debug-%s-r%d-%s.json", strings.ToLower(code), r.Summary.Round, r.Summary.Phase)
}

// ReplayBattle re-runs one of the round's recorded battles — index 0 is the
// first pairing, matching Game.Battles — against a fresh copy of the captured
// game. The recording supplies the dice, so the fight plays out exactly as it
// did for the player, right down to the event text. Compare the result against
// the recorded one to see whether the engine still does what it did, or step
// through it to find where it went wrong.
func (r *DebugReport) ReplayBattle(i int) (*BattleResult, error) {
	g, err := r.Game()
	if err != nil {
		return nil, err
	}
	if i < 0 || i >= len(g.Battles) {
		return nil, fmt.Errorf("no battle %d in this report (it has %d)", i, len(g.Battles))
	}
	rec := g.Battles[i]
	if len(rec.Seats) != 2 || len(rec.Lineups) != 2 {
		return nil, fmt.Errorf("battle %d has no recorded lineups to replay", i)
	}
	for _, seat := range rec.Seats {
		if seat < 0 || seat >= len(g.Players) {
			return nil, fmt.Errorf("battle %d names seat %d, which isn't at this table", i, seat)
		}
	}
	// Refuse rather than hand back a battle that quietly differs from the one
	// the player saw: a game saved before the engine recorded its dice can only
	// be re-rolled, not replayed.
	if !rec.Replayable() {
		return nil, fmt.Errorf("battle %d predates dice recording, so it can't be replayed faithfully — "+
			"its lineups are in the report, and ReplayResult will fight it again with fresh dice", i)
	}
	// Rewind the two fighters to how they went in: the round has since cleared
	// their banks and written their Mana back, and the battle itself spent card
	// ids minting apples.
	applyBattleInputs(g, rec)
	g.Round = rec.Round
	g.NextCardID = rec.StartCardID
	g.drawReplay = append([]int(nil), rec.Draws...)
	return g.runBattle(rec.Seats[0], rec.Seats[1]), nil
}

// Text renders the report for reading.
func (r *DebugReport) Text() string {
	var b strings.Builder
	g, err := r.Game()
	if err != nil {
		fmt.Fprintf(&b, "debug report v%d — UNREADABLE STATE: %v\n", r.Version, err)
		return b.String()
	}

	fmt.Fprintf(&b, "Super Auto Pets debug report (v%d)\n", r.Version)
	if r.CapturedAt != "" {
		fmt.Fprintf(&b, "captured %s\n", r.CapturedAt)
	}
	if r.Note != "" {
		fmt.Fprintf(&b, "note: %s\n", r.Note)
	}
	packs := strings.Join(g.packList(), " + ")
	fmt.Fprintf(&b, "\ngame %s · code %s · packs %s\n", g.ID, g.Code, packs)
	fmt.Fprintf(&b, "round %d/%d · phase %s · %d players\n", g.Round, MaxRounds, g.Phase, len(g.Players))
	fmt.Fprintf(&b, "priority seat %d · shop turn seat %d · next card id %d\n",
		g.PrioritySeat, g.Turn, g.NextCardID)
	if g.Phase == PhaseGameOver {
		fmt.Fprintf(&b, "winner: %s\n", seatList(g, g.WinnerSeats))
	}
	if pairs := g.Pairings(); len(pairs) > 0 {
		var parts []string
		for _, m := range pairs {
			parts = append(parts, fmt.Sprintf("%d v %d", m[0], m[1]))
		}
		fmt.Fprintf(&b, "this round's pairings: %s\n", strings.Join(parts, ", "))
	}

	b.WriteString("\n=== Players ===\n")
	for _, p := range g.Players {
		writePlayer(&b, p)
	}

	b.WriteString("\n=== Shop ===\n")
	writeShop(&b, g)

	if len(g.Battles) > 0 {
		fmt.Fprintf(&b, "\n=== Battles (round %d) ===\n", g.Battles[0].Round)
		for i, res := range g.Battles {
			writeBattle(&b, g, i, res)
		}
	}

	fmt.Fprintf(&b, "\n=== Event log (%d entries) ===\n", len(g.Log))
	for _, e := range g.Log {
		seat := "  -"
		if e.Seat >= 0 {
			seat = fmt.Sprintf("s%d", e.Seat)
		}
		fmt.Fprintf(&b, "  #%-4d r%d %-8s %-3s %s %s", e.Seq, e.Round, e.Phase, seat, e.Icon, e.Text)
		if e.Kind != "" {
			fmt.Fprintf(&b, "  [kind=%s]", e.Kind)
		}
		b.WriteString("\n")
	}

	b.WriteString("\n=== Reproducing this ===\n")
	b.WriteString(r.GoTest())
	return b.String()
}

// GoTest is a paste-ready test that reproduces the report's battle. Save the
// report's JSON next to it and the test replays the exact fight — same
// lineups, same dice — so you can assert on what should have happened and then
// step into the resolver to find out why it didn't.
func (r *DebugReport) GoTest() string {
	var b strings.Builder
	name := r.Filename()
	fmt.Fprintf(&b, "Save the JSON report as internal/game/testdata/%s, then in\n"+
		"internal/game (package game):\n\n", name)
	fmt.Fprintf(&b, "func TestReproFrom%s(t *testing.T) {\n", identifier(r.Summary.Code))
	fmt.Fprintf(&b, "\trep, err := LoadDebugReportFile(\"testdata/%s\")\n", name)
	b.WriteString("\tif err != nil {\n\t\tt.Fatal(err)\n\t}\n")
	b.WriteString("\tres, err := rep.ReplayBattle(0) // 0 = the round's first pairing\n")
	b.WriteString("\tif err != nil {\n\t\tt.Fatal(err)\n\t}\n")
	b.WriteString("\tfor i, ev := range res.Events {\n\t\tt.Logf(\"%3d %-8s %s\", i, ev.Type, ev.Text)\n\t}\n")
	// The assertion is seeded with what actually happened, since that's the
	// thing under suspicion: flip it to what should have happened and the test
	// becomes the bug report.
	winner := -1
	if g, err := r.Game(); err == nil && len(g.Battles) > 0 {
		winner = g.Battles[0].WinnerSeat
	}
	outcome := fmt.Sprintf("seat %d to win", winner)
	if winner < 0 {
		outcome = "a draw"
	}
	fmt.Fprintf(&b, "\tif res.WinnerSeat != %d { // what happened; assert what should have\n", winner)
	fmt.Fprintf(&b, "\t\tt.Fatalf(\"expected %s, got winner seat %%d\", res.WinnerSeat)\n", outcome)
	b.WriteString("\t}\n}\n\n")
	b.WriteString("The whole game is there too, not just the battle: rep.Game() hands back\n" +
		"the exact state the server held, so you can carry on from the shop, replay\n" +
		"a different pairing, or read a deck card by card.\n")
	return b.String()
}

// writePlayer renders one seat: its banks, then its deck in order.
func writePlayer(b *strings.Builder, p *Player) {
	who := "human"
	if p.IsBot {
		who = fmt.Sprintf("bot %.2f", p.BotLevel)
	}
	conn := "connected"
	if !p.Connected {
		conn = "DISCONNECTED"
	}
	ready := ""
	if p.Ready {
		ready = " · ready/passed"
	}
	wins := ""
	if len(p.RoundWins) > 0 {
		wins = fmt.Sprintf(" (won rounds %v)", p.RoundWins)
	}
	fmt.Fprintf(b, "\nSeat %d  %s  (%s, %s)%s\n", p.Seat, p.Name, who, conn, ready)
	fmt.Fprintf(b, "  %d coins · %d trophies%s · %d pets\n", p.Coins, p.Trophies, wins, p.PetCount())
	var banks []string
	for _, bank := range []struct {
		label string
		n     int
	}{
		{"mana", p.Mana}, {"avocados", p.Avocados}, {"trumpets banked", p.PendingTrumpets},
		{"apples in play next battle", p.PendingApplesInPlay}, {"apples next round", p.NextRoundApples},
		{"buys this round", p.BuysThisRound},
	} {
		if bank.n != 0 {
			banks = append(banks, fmt.Sprintf("%s %d", bank.label, bank.n))
		}
	}
	if p.FirstBuyFree {
		banks = append(banks, "first buy free")
	}
	if p.TripledThisRound {
		banks = append(banks, "tripled this round")
	}
	if len(banks) > 0 {
		fmt.Fprintf(b, "  %s\n", strings.Join(banks, " · "))
	}
	if p.ShopPeek != nil {
		fmt.Fprintf(b, "  peeked at the shop deck: %s\n", cardLine(*p.ShopPeek))
	}
	fmt.Fprintf(b, "  deck, in order (%d):\n", len(p.Deck))
	if len(p.Deck) == 0 {
		b.WriteString("    (empty)\n")
	}
	for i, c := range p.Deck {
		fmt.Fprintf(b, "    %d. %s\n", i+1, cardLine(c))
	}
}

// writeShop renders the shop row, what's left in each tier deck, the discards,
// and any choice a player is mid-way through.
func writeShop(b *strings.Builder, g *Game) {
	if len(g.ShopRow) == 0 {
		b.WriteString("  row: (none — the shop is closed)\n")
	}
	for i, c := range g.ShopRow {
		if c.ID == "" {
			fmt.Fprintf(b, "  row %d: (bought)\n", i)
			continue
		}
		fmt.Fprintf(b, "  row %d: %s\n", i, cardLine(c))
	}
	for tier, deck := range g.ShopDecks {
		fmt.Fprintf(b, "  tier %d deck: %d left", tier+1, len(deck))
		// The order is the whole point of dumping the deck: it decides what the
		// next buy, peek or trade-in turns up.
		if len(deck) > 0 {
			fmt.Fprintf(b, " — next: %s", cardNames(deck[:min(len(deck), 6)]))
		}
		b.WriteString("\n")
	}
	for tier := 1; tier <= MaxRounds; tier++ {
		if pile := g.Discards[tier]; len(pile) > 0 {
			fmt.Fprintf(b, "  tier %d discards: %s\n", tier, cardNames(pile))
		}
	}
	if t := g.Pending; t != nil {
		fmt.Fprintf(b, "  PENDING trade-in by %s from tier %d: %s | %s\n",
			playerName(g, t.PlayerID), t.Tier, cardLine(t.Options[0]), cardLine(t.Options[1]))
	}
	if rv := g.PendingReveal; rv != nil {
		fmt.Fprintf(b, "  PENDING reveal by %s (source %s, %d apples), options %v\n",
			playerName(g, rv.PlayerID), rv.Source, rv.Apples, rv.Options)
	}
	if s := g.PendingSacrifice; s != nil {
		fmt.Fprintf(b, "  PENDING sacrifice by %s (source %s, tier %d), options %v\n",
			playerName(g, s.PlayerID), s.Source, s.Tier, s.Options)
	}
}

// writeBattle renders one battle: who fought, what they fielded, the dice it
// rolled, every event in order, and how it ended.
func writeBattle(b *strings.Builder, g *Game, i int, res *BattleResult) {
	fmt.Fprintf(b, "\n-- battle %d: ", i)
	if len(res.Seats) == 2 {
		fmt.Fprintf(b, "seat %d (%s, first) v seat %d (%s) --\n",
			res.Seats[0], seatName(g, res.Seats[0]), res.Seats[1], seatName(g, res.Seats[1]))
	} else {
		fmt.Fprintf(b, "seats %v --\n", res.Seats)
	}
	outcome := "a draw"
	if res.WinnerSeat >= 0 {
		outcome = fmt.Sprintf("seat %d (%s) won %d trophy(s)",
			res.WinnerSeat, seatName(g, res.WinnerSeat), res.Trophies)
	}
	fmt.Fprintf(b, "  outcome: %s · survivors by side %v\n", outcome, res.Survivors)
	for side, lineup := range res.Lineups {
		fmt.Fprintf(b, "  side %d (seat %d) fielded, top of deck first:\n", side, res.SeatOf(side))
		for j, c := range lineup {
			fmt.Fprintf(b, "    %d. %s\n", j+1, cardLine(c))
		}
		if side < len(res.Inputs) {
			in := res.Inputs[side]
			fmt.Fprintf(b, "    started with: %d mana, %d trumpets, %d apples in play\n",
				in.Mana, in.Trumpets, in.ApplesInPlay)
		}
	}
	if res.Replayable() {
		fmt.Fprintf(b, "  dice tape (%d draws): %v\n", len(res.Draws), res.Draws)
	} else {
		b.WriteString("  dice tape: NOT RECORDED — this battle was played before the engine\n" +
			"    recorded its dice, so it can only be re-fought, not replayed\n")
	}
	fmt.Fprintf(b, "  events (%d):\n", len(res.Events))
	for j, ev := range res.Events {
		fmt.Fprintf(b, "    %3d %-9s side %d", j, ev.Type, ev.Seat)
		if ev.Card != nil {
			fmt.Fprintf(b, " %s", ev.Card.Name)
		}
		if len(ev.Dice) > 0 {
			fmt.Fprintf(b, " dice=%v(%d)", ev.Dice, ev.Roll)
		}
		if len(ev.Damage) > 0 {
			fmt.Fprintf(b, " dmg=%v died=%v", ev.Damage, ev.Died)
		}
		if ev.Count != 0 {
			fmt.Fprintf(b, " count=%d", ev.Count)
		}
		if ev.Text != "" {
			fmt.Fprintf(b, " · %s", ev.Text)
		}
		b.WriteString("\n")
	}
}

// cardLine describes one card in full: what it is, what it does, and the id the
// log and battle events refer to it by.
func cardLine(c Card) string {
	var b strings.Builder
	b.WriteString(c.Name)
	switch {
	case c.IsPet():
		fmt.Fprintf(&b, " (pet, power %d", c.Power)
		if c.Suit != "" {
			fmt.Fprintf(&b, ", %s", c.Suit)
		}
	case c.IsAilment():
		fmt.Fprintf(&b, " (ailment %s", c.Ailment)
	default:
		b.WriteString(" (food")
		if c.Food != "" {
			fmt.Fprintf(&b, " %s", c.Food)
		}
		if c.Perk {
			b.WriteString(", perk")
		}
	}
	if c.Tier > 0 {
		fmt.Fprintf(&b, ", tier %d", c.Tier)
	}
	if c.Temporary {
		b.WriteString(", temporary")
	}
	fmt.Fprintf(&b, ", id %s)", c.ID)
	if c.EffectText != "" {
		fmt.Fprintf(&b, " — %s", c.EffectText)
	}
	return b.String()
}

// cardNames lists cards by name alone, for places where the detail would drown
// the point (deck order, discard piles).
func cardNames(cards []Card) string {
	names := make([]string, len(cards))
	for i, c := range cards {
		names[i] = c.Name
	}
	return strings.Join(names, ", ")
}

func seatName(g *Game, seat int) string {
	if seat < 0 || seat >= len(g.Players) {
		return "?"
	}
	return g.Players[seat].Name
}

func seatList(g *Game, seats []int) string {
	if len(seats) == 0 {
		return "(none)"
	}
	names := make([]string, len(seats))
	for i, s := range seats {
		names[i] = fmt.Sprintf("seat %d (%s)", s, seatName(g, s))
	}
	return strings.Join(names, ", ")
}

// identifier makes a string safe to paste into a Go function name.
func identifier(s string) string {
	var b strings.Builder
	for _, r := range strings.ToUpper(s) {
		if r >= 'A' && r <= 'Z' || r >= '0' && r <= '9' {
			b.WriteRune(r)
		}
	}
	if b.Len() == 0 || b.String()[0] >= '0' && b.String()[0] <= '9' {
		return "Game" + b.String()
	}
	return b.String()
}

func playerName(g *Game, playerID string) string {
	if p := g.PlayerByID(playerID); p != nil {
		return fmt.Sprintf("seat %d (%s)", p.Seat, p.Name)
	}
	return playerID
}