class_name AI
## KI mit Vorausschau: jede mögliche Aktion wird auf einer Kopie des Spiels
## ausgeführt und die Stellung danach bewertet; die besten Erstschritte werden um
## einen Folgeschritt vertieft. Die gierige Variante (choose_action_greedy) dient
## als Vergleich und für die Schwierigkeit Leicht. Alles hier ist zustandslos und
## darf in einem Hintergrund-Thread auf einer Spielkopie laufen.


# --- Bewertung -------------------------------------------------------------------

static func creature_value(c: Game.Creature) -> float:
    var v := float(c.power() + c.health)
    if c.taunt():
        v += 2.0
    if c.shield:
        v += 1.5
    if c.attacks_per_turn() == 2:
        v += c.power()
    if c.frozen:
        v -= c.power()  # setzt den nächsten Angriff aus: der Angriffswert zählt nicht
    if not c.ready:
        v -= c.power() * 0.25
    return v


static func board_value(p: Game.Player) -> float:
    var v := 0.0
    for c in p.board:
        v += creature_value(c)
    return v


## Stellung aus Sicht von p: eigenes Leben, Feld und Hand zählen positiv, die der Gegner
## negativ, der stärkste Gegner etwas mehr (jeder gegen jeden: den Führenden bremsen).
## Gegnerische Angriffskraft ohne eigenen Wächter ist eine Bedrohung, tödliche besonders.
static func evaluate(g: Game, p: Game.Player) -> float:
    if not p.alive():
        return -10000.0
    var score := p.life * 1.0 + board_value(p) * 1.0 + p.hand.size() * 0.8 + p.traps.size() * 2.5
    var alive_enemies := 0
    var threat := 0.0
    var leader := 0.0
    for e in g.players:
        if e == p:
            continue
        if not e.alive():
            score += 40.0
            continue
        alive_enemies += 1
        var ev: float = e.life * 0.6 + board_value(e) * 0.9 + e.hand.size() * 0.2
        score -= ev
        leader = maxf(leader, ev)
        if e.life <= 6:
            score += 3.0  # fast besiegt: dranbleiben
        for c in e.board:
            if not c.frozen:
                threat += c.power() * c.attacks_per_turn()
    if alive_enemies == 0:
        return 10000.0
    score -= leader * 0.25
    var guarded := false
    for c in p.board:
        if c.taunt():
            guarded = true
            break
    if guarded:
        score -= threat * 0.1
    elif threat >= p.life:
        score -= 25.0
    else:
        score -= threat * 0.3
    return score


# --- Vorausschau ---------------------------------------------------------------

const MAX_TARGETS := 4   # je Karte bzw. Angreifer nur die aussichtsreichsten Ziele prüfen
const DEEPEN := 8        # so viele beste Erstschritte bekommen Folgeschritte
const FOLLOW_UPS := 10   # Folgeschritte je vertieftem Kandidat
static var time_budget_ms := 150  # Zeitbudget je Entscheidung; danach der beste bisherige Zug


## Grobe Rangfolge eines Ziels für einen Karteneffekt (nur zum Vorsortieren).
static func _target_rank(kind: String, amount: int, t) -> float:
    if t is Game.Player:
        return 50.0 - t.life if kind == "damage" else 0.0
    match kind:
        "damage":
            return 100.0 + _value(t) if not t.shield and t.health <= amount else float(_value(t))
        "freeze", "bounce":
            return t.card.cost * 10.0 + t.power()
        "buff", "shield":
            return (100.0 if t.can_attack() else 0.0) + t.power()
    return float(_value(t))


## Rangfolge eines Angriffsziels: sichere Abtausche zuerst, dann Helden, dann der Rest.
static func _attack_rank(cr: Game.Creature, t) -> float:
    if t is Game.Player:
        return 50.0 - t.life
    if _kills(cr, t):
        return (100.0 if not _kills(t, cr) else 60.0) + _value(t)
    return -float(t.health)


static func _top(list: Array, rank: Callable, n: int) -> Array:
    if list.size() <= n:
        return list
    var ranked := []
    for t in list:
        ranked.append([rank.call(t), t])
    ranked.sort_custom(func(a, b): return a[0] > b[0])
    return ranked.slice(0, n).map(func(pair): return pair[1])


## Mögliche Aktionen; mit prune nur die MAX_TARGETS besten Ziele je Karte und Angreifer.
static func candidate_actions(game: Game, p: Game.Player, prune: bool = false) -> Array:
    var out := []
    var valid_cache := {}
    for card in p.hand:
        if not game.can_play(p, card)[0]:
            continue
        var tt: String = card.target_type()
        if tt == "":
            out.append({"type": "play", "card": card, "target": null})
            continue
        if not valid_cache.has(tt):
            valid_cache[tt] = game.valid_targets(p, tt)
        var valid: Array = valid_cache[tt]
        if valid.is_empty():
            out.append({"type": "play", "card": card, "target": null})
            continue
        if prune:
            var fx: Cards.Effect = null
            for f in card.effects:
                if f.target == tt:
                    fx = f
                    break
            var kind: String = fx.kind if fx != null else ""
            var amount: int = fx.amount if fx != null else 0
            var key := "%s/%s/%d" % [tt, kind, amount]
            if not valid_cache.has(key):
                valid_cache[key] = _top(valid, func(t): return _target_rank(kind, amount, t), MAX_TARGETS)
            valid = valid_cache[key]
        for t in valid:
            out.append({"type": "play", "card": card, "target": t})
    for cr in p.board:
        if not cr.can_attack():
            continue
        var targets := []
        for e in game.enemies_of(p):
            for t in e.board + [e]:
                if game.can_attack(cr, t)[0]:
                    targets.append(t)
        if prune:
            targets = _top(targets, func(t): return _attack_rank(cr, t), MAX_TARGETS)
        for t in targets:
            out.append({"type": "attack", "creature": cr, "target": t})
    return out


## Führt eine Aktion des Originals auf der Kopie aus.
static func apply_on_clone(g2: Game, game: Game, action: Dictionary) -> void:
    var p2: Game.Player = g2.players[game.current_idx]
    var target = null
    if action.get("target") != null:
        target = map_target(g2, game, action.target)
    if action.type == "play":
        g2.play_card(p2, action.card, target)
    else:
        g2.attack(g2.find_creature(action.creature.uid), target)


static func map_target(g2: Game, game: Game, t):
    if t is Game.Creature:
        return g2.find_creature(t.uid)
    return g2.players[game.players.find(t)]


## Überträgt eine auf der Kopie gewählte Aktion zurück auf das Original.
static func map_action(game: Game, copy: Game, action: Dictionary) -> Dictionary:
    var out := action.duplicate()
    if action.has("creature"):
        out["creature"] = game.find_creature(action.creature.uid)
    if action.get("target") != null:
        out["target"] = map_target(game, copy, action.target)
    return out


## Mulligan der KI: teure Karten im ersten Zug zurücklegen.
static func mulligan_cards(p: Game.Player) -> Array:
    return p.hand.filter(func(c): return c.cost >= 5)


## Beste Aktion nach einer Vorausschau von zwei Schritten: erst wird jede Aktion auf einer
## Kopie ausgeführt und bewertet, dann bekommen die DEEPEN besten Folgeschritte
## (z. B. verstärken, dann angreifen). Bei Zeitmangel gilt der beste bisherige Zug.
static func choose_action(game: Game, p: Game.Player) -> Dictionary:
    if game.winner != "" or game.enemies_of(p).is_empty():
        return {"type": "end"}
    if not p.mulligan_done and p.turns == 1 and p == game.current():
        return {"type": "mulligan", "cards": mulligan_cards(p)}
    var t0 := Time.get_ticks_msec()
    var base := evaluate(game, p) + 0.01
    var firsts := []  # {action, game, score}
    for action in candidate_actions(game, p, true):
        if not firsts.is_empty() and Time.get_ticks_msec() - t0 > time_budget_ms:
            break
        var g2 := game.clone_for(p)
        apply_on_clone(g2, game, action)
        firsts.append({"action": action, "game": g2, "score": evaluate(g2, g2.players[game.current_idx])})
    firsts.sort_custom(func(a, b): return a.score > b.score)
    var best := {"type": "end"}
    var best_score := base
    for i in mini(firsts.size(), DEEPEN):
        var f: Dictionary = firsts[i]
        var g2: Game = f.game
        var score: float = f.score
        if g2.winner == "":
            var p2: Game.Player = g2.players[game.current_idx]
            var count := 0
            for nxt in candidate_actions(g2, p2, true):
                if count >= FOLLOW_UPS or Time.get_ticks_msec() - t0 > time_budget_ms:
                    break
                count += 1
                var g3 := g2.clone_for(p2)
                apply_on_clone(g3, g2, nxt)
                score = maxf(score, evaluate(g3, g3.players[game.current_idx]) - 0.001)
        if score > best_score:
            best_score = score
            best = f.action
    # Erstschritte ohne Vertiefung zählen mit ihrer Einzelbewertung
    for i in range(DEEPEN, firsts.size()):
        if firsts[i].score > best_score:
            best_score = firsts[i].score
            best = firsts[i].action
    return best


# --- Gierige Vergleichs-KI -------------------------------------------------------

static func _kills(attacker, defender) -> bool:
    return not defender.shield and defender.health <= attacker.power()


static func _value(c) -> int:
    return c.power() + c.health + (2 if c.taunt() else 0)


static func _best(arr: Array, key: Callable):
    var best = null
    var best_v := 0
    for x in arr:
        var v: int = key.call(x)
        if best == null or v > best_v:
            best = x
            best_v = v
    return best


static func _threat_score(h) -> int:
    var board_attack := 0
    for c in h.board:
        board_attack += c.power()
    return h.life - board_attack


static func _weakest(heroes: Array):
    var best = null
    for h in heroes:
        if best == null or _threat_score(h) < _threat_score(best):
            best = h
    return best


static func choose_action_greedy(game: Game, p: Game.Player) -> Dictionary:
    if game.winner != "" or game.enemies_of(p).is_empty():
        return {"type": "end"}
    if not p.mulligan_done and p.turns == 1 and p == game.current():
        return {"type": "mulligan", "cards": mulligan_cards(p)}
    var playable := p.hand.filter(func(c): return game.can_play(p, c)[0])
    if not playable.is_empty():
        Game.shuffle(playable, game.rng)
        var card = playable[0]
        for c in playable:
            if c.cost > card.cost:
                card = c
        return {"type": "play", "card": card, "target": pick_target(game, p, card)}
    for cr in p.board:
        if cr.can_attack():
            var t = pick_attack_target(game, p, cr)
            if t != null:
                return {"type": "attack", "creature": cr, "target": t}
    return {"type": "end"}


static func pick_target(game: Game, p: Game.Player, card: Cards.Card):
    var tt := card.target_type()
    if tt == "":
        return null
    var valid := game.valid_targets(p, tt)
    if valid.is_empty():
        return null
    var fx: Cards.Effect = null
    for f in card.effects:
        if f.target == tt:
            fx = f
            break
    var creatures := valid.filter(func(t): return t is Game.Creature)
    var heroes := valid.filter(func(t): return t is Game.Player)
    match fx.kind:
        "damage":
            var killable := creatures.filter(func(c): return not c.shield and c.health <= fx.amount)
            if not killable.is_empty():
                return _best(killable, Callable(AI, "_value"))
            if not heroes.is_empty():
                return _weakest(heroes)
            return _best(creatures, Callable(AI, "_value"))
        "freeze", "bounce":
            return _best(creatures, func(c): return c.card.cost * 100 + c.power())
        "buff", "shield":
            return _best(creatures, func(c): return (100 if c.can_attack() else 0) + c.power())
    return valid[0]


static func pick_attack_target(game: Game, p: Game.Player, cr: Game.Creature):
    var enemies := game.enemies_of(p)
    var total := 0
    for c in p.board:
        if c.can_attack():
            total += c.power() * c.attacks_left
    var options := []
    for e in enemies:
        var taunts: Array = e.board.filter(func(c): return c.taunt())
        if not taunts.is_empty():
            options.append_array(taunts)
        else:
            if total >= e.life:
                return e
            options.append_array(e.board)
            options.append(e)
    var creatures := options.filter(func(t): return t is Game.Creature)
    var heroes := options.filter(func(t): return t is Game.Player)
    var good := creatures.filter(func(c): return _kills(cr, c) and not _kills(c, cr))
    if not good.is_empty():
        return _best(good, Callable(AI, "_value"))
    var trade := creatures.filter(func(c): return _kills(cr, c) and _value(c) > _value(cr))
    if not trade.is_empty():
        return _best(trade, Callable(AI, "_value"))
    if not heroes.is_empty():
        return _weakest(heroes)
    if not creatures.is_empty():
        return _best(creatures, func(c): return 1000 - c.health)
    return null


# --- Ausführung -------------------------------------------------------------------

static func apply_action(game: Game, p: Game.Player, action: Dictionary) -> void:
    match action.type:
        "play":
            game.play_card(p, action.card, action.target)
        "attack":
            game.attack(action.creature, action.target)
        "mulligan":
            game.mulligan(p, action.cards)
        _:
            game.end_turn()


## Spielt den ganzen Zug (für Simulationen und Tests). greedy: gierige KI statt Vorausschau.
static func take_turn(game: Game, p: Game.Player, greedy: bool = false, limit: int = 100) -> void:
    for i in limit:
        var action := choose_action_greedy(game, p) if greedy else choose_action(game, p)
        apply_action(game, p, action)
        if action.type == "end" or game.winner != "":
            return