class_name AI
## KI mit einfacher Vorausschau: jede mögliche Aktion wird auf einer Kopie des
## Spiels ausgeführt und die Stellung danach bewertet. Die gierige Variante
## (choose_action_greedy) dient als Vergleich.


# --- 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() * 0.5
    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. Ein besiegter Gegner ist viel wert.
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
    for e in g.players:
        if e == p:
            continue
        if not e.alive():
            score += 40.0
            continue
        alive_enemies += 1
        score -= e.life * 0.6 + board_value(e) * 0.9 + e.hand.size() * 0.2
        if e.life <= 6:
            score += 3.0  # fast besiegt: dranbleiben
    if alive_enemies == 0:
        return 10000.0
    return score


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

static func candidate_actions(game: Game, p: Game.Player) -> Array:
    var out := []
    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})
        else:
            var valid := game.valid_targets(p, tt)
            if valid.is_empty():
                out.append({"type": "play", "card": card, "target": null})
            for t in valid:
                out.append({"type": "play", "card": card, "target": t})
    for cr in p.board:
        if not cr.can_attack():
            continue
        for e in game.enemies_of(p):
            for t in e.board + [e]:
                if game.can_attack(cr, t)[0]:
                    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)]


const FOLLOW_UPS := 10  # Folgeschritte je Kandidat in der zweiten Suchstufe


## 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: jede Aktion wird auf einer
## Kopie ausgeführt und mit ihrem besten Folgeschritt bewertet (z. B. verstärken, dann angreifen).
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 best := {"type": "end"}
    var best_score := evaluate(game, p) + 0.01
    for action in candidate_actions(game, p):
        var g2 := game.clone_for(p)
        apply_on_clone(g2, game, action)
        var p2: Game.Player = g2.players[game.current_idx]
        var score := evaluate(g2, p2)
        if g2.winner == "":
            var count := 0
            for f in candidate_actions(g2, p2):
                if count >= FOLLOW_UPS:
                    break
                count += 1
                var g3 := g2.clone_for(p2)
                apply_on_clone(g3, g2, f)
                score = maxf(score, evaluate(g3, g3.players[g2.current_idx]) - 0.001)
        if score > best_score:
            best_score = score
            best = 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