deckbelcher / src / lib / deck-validation / rules / commander.ts

import { getCardsInSection, isKnownSection } from "@/lib/deck-types";
import type { Card } from "@/lib/scryfall-types";
import {
	asRuleNumber,
	type Rule,
	type ValidationContext,
	type Violation,
	violation,
} from "../types";
import { getFrontFaceTypeLine, getOracleText, getTypeLine } from "../utils";

/**
 * Commander required - at least one commander
 */
export const commanderRequiredRule: Rule<"commanderRequired"> = {
	id: "commanderRequired",
	rule: asRuleNumber("903.3"),
	ruleText:
		"Each deck has a legendary card designated as its commander. That card must be either (a) a creature card, (b) a Vehicle card, or (c) a Spacecraft card with one or more power/toughness boxes. This designation is not a characteristic of the object represented by the card; rather, it is an attribute of the card itself. The card retains this designation even when it changes zones.",
	category: "structure",
	description: "Deck must have at least one commander",
	validate(ctx: ValidationContext): Violation[] {
		const { deck } = ctx;
		const commanders = getCardsInSection(deck, "commander");
		const commanderCount = commanders.reduce((sum, c) => sum + c.quantity, 0);

		if (commanderCount === 0) {
			return [violation(this, "Deck must have a commander", "error")];
		}

		return [];
	},
};

/**
 * Commander must be legendary creature, vehicle, or spacecraft
 * (or any card with "can be your commander" text)
 *
 * As of 2024, vehicles and spacecraft can be commanders without
 * special text - they're allowed by the base Commander rules.
 */
export const commanderLegendaryRule: Rule<"commanderLegendary"> = {
	id: "commanderLegendary",
	rule: asRuleNumber("903.3"),
	ruleText:
		"Each deck has a legendary card designated as its commander. That card must be either (a) a creature card, (b) a Vehicle card, or (c) a Spacecraft card with one or more power/toughness boxes. This designation is not a characteristic of the object represented by the card; rather, it is an attribute of the card itself. The card retains this designation even when it changes zones.",
	category: "structure",
	description:
		"Commander must be a legendary creature, vehicle, or spacecraft with P/T",
	validate(ctx: ValidationContext): Violation[] {
		const { deck, cardLookup } = ctx;
		const violations: Violation[] = [];
		const commanders = getCardsInSection(deck, "commander");

		for (const entry of commanders) {
			const card = cardLookup(entry.scryfallId);
			if (!card) continue;

			if (!isValidCommanderType(card)) {
				violations.push(
					violation(this, `${card.name} is not a legendary creature`, "error", {
						cardName: card.name,
						oracleId: entry.oracleId,
						section: "commander",
					}),
				);
			}
		}

		return violations;
	},
};

/**
 * Check if card has a creature type valid for commander (creature, vehicle, spacecraft with P/T).
 * Shared between regular Commander and PDH validation.
 *
 * For DFCs/MDFCs, checks the FRONT FACE only - a Saga that transforms into
 * a creature (e.g., Behold the Unspeakable) is NOT a legal commander.
 */
export function hasCommanderCreatureType(card: Card): boolean {
	const typeLine = getFrontFaceTypeLine(card).toLowerCase();

	if (typeLine.includes("creature")) return true;
	if (typeLine.includes("vehicle")) return true;

	// Spacecraft need P/T box to be valid (903.3c)
	if (typeLine.includes("spacecraft")) {
		return card.power != null && card.toughness != null;
	}

	return false;
}

export function isValidCommanderType(card: Card): boolean {
	// Silver-bordered and acorn cards can't be commanders in sanctioned play
	if (card.border_color === "silver" || card.security_stamp === "acorn") {
		return false;
	}

	const frontTypeLine = getFrontFaceTypeLine(card).toLowerCase();
	const oracleText = getOracleText(card).toLowerCase();

	const isLegendary = frontTypeLine.includes("legendary");
	const canBeCommander = oracleText.includes("can be your commander");

	// Grist-style cards: creatures in all zones except battlefield
	// e.g., "As long as Grist isn't on the battlefield, it's a 1/1 Insect creature"
	const isCreatureOutsideBattlefield =
		/isn't on the battlefield.*it's a.*creature/i.test(oracleText);

	// Legendary creature/vehicle/spacecraft (with P/T for spacecraft)
	if (isLegendary && hasCommanderCreatureType(card)) {
		return true;
	}

	// Cards with explicit "can be your commander" text
	if (canBeCommander) {
		return true;
	}

	// Legendary cards that are creatures outside the battlefield (Grist)
	if (isLegendary && isCreatureOutsideBattlefield) {
		return true;
	}

	return false;
}

/**
 * Partner rule - validates commander pairing is legal
 *
 * Legal pairings:
 * - Both have generic "Partner" (not "Partner with X")
 * - Both have "Friends forever"
 * - One has "Partner with [NAME]" and the other is that NAME
 * - One has "Choose a Background" and other is a Background enchantment
 */
export const commanderPartnerRule: Rule<"commanderPartner"> = {
	id: "commanderPartner",
	rule: asRuleNumber("702.124a"),
	ruleText:
		"Partner abilities are keyword abilities that modify the rules for deck construction in the Commander variant (see rule 903), and they function before the game begins. Each partner ability allows you to designate two legendary cards as your commander rather than one. Each partner ability has its own requirements for those two commanders. The partner abilities are: partner, partner—[text], partner with [name], friends forever, choose a Background, and Doctor's companion.",
	category: "structure",
	description: "Multiple commanders must have valid partner pairing",
	validate(ctx: ValidationContext): Violation[] {
		const { deck, cardLookup } = ctx;
		const commanders = getCardsInSection(deck, "commander");

		// Expand commanders by quantity
		const commanderCards: Card[] = [];
		for (const entry of commanders) {
			const card = cardLookup(entry.scryfallId);
			if (!card) continue;
			for (let i = 0; i < entry.quantity; i++) {
				commanderCards.push(card);
			}
		}

		if (commanderCards.length <= 1) return [];

		if (commanderCards.length > 2) {
			return [
				violation(
					this,
					`Deck has ${commanderCards.length} commanders, maximum is 2`,
					"error",
				),
			];
		}

		const [card1, card2] = commanderCards;
		const pairingResult = validatePairing(card1, card2);

		if (!pairingResult.valid) {
			return [
				violation(
					this,
					`${card1.name} and ${card2.name} cannot be paired: ${pairingResult.reason}`,
					"error",
				),
			];
		}

		return [];
	},
};

/**
 * Validate if two cards can legally be paired as commanders
 */
function validatePairing(
	card1: Card,
	card2: Card,
): { valid: true } | { valid: false; reason: string } {
	const info1 = getPartnerInfo(card1);
	const info2 = getPartnerInfo(card2);

	// Generic partner: both must have it
	if (info1.hasGenericPartner && info2.hasGenericPartner) {
		return { valid: true };
	}

	// Friends forever: both must have it
	if (info1.hasFriendsForever && info2.hasFriendsForever) {
		return { valid: true };
	}

	// Partner with: check if they name each other (case-insensitive)
	if (
		info1.partnerWithName &&
		info1.partnerWithName.toLowerCase() === card2.name.toLowerCase()
	) {
		return { valid: true };
	}
	if (
		info2.partnerWithName &&
		info2.partnerWithName.toLowerCase() === card1.name.toLowerCase()
	) {
		return { valid: true };
	}

	// Background pairing: one chooses background, other is background
	if (info1.choosesBackground && info2.isBackground) {
		return { valid: true };
	}
	if (info2.choosesBackground && info1.isBackground) {
		return { valid: true };
	}

	// Doctor's companion: can pair with a Doctor (Time Lord Doctor creature)
	if (info1.hasDoctorsCompanion && isDoctor(card2)) {
		return { valid: true };
	}
	if (info2.hasDoctorsCompanion && isDoctor(card1)) {
		return { valid: true };
	}

	// No valid pairing found
	const getAbilityName = (info: PartnerInfo): string => {
		if (info.hasGenericPartner) return "Partner";
		if (info.hasFriendsForever) return "Friends forever";
		if (info.partnerWithName) return `Partner with ${info.partnerWithName}`;
		if (info.choosesBackground) return "Choose a Background";
		if (info.isBackground) return "Background";
		if (info.hasDoctorsCompanion) return "Doctor's companion";
		return "no partner ability";
	};

	return {
		valid: false,
		reason: `${getAbilityName(info1)} cannot pair with ${getAbilityName(info2)}`,
	};
}

export interface PartnerInfo {
	hasGenericPartner: boolean;
	hasFriendsForever: boolean;
	partnerWithName: string | null;
	choosesBackground: boolean;
	isBackground: boolean;
	hasDoctorsCompanion: boolean;
}

export function getPartnerInfo(card: Card): PartnerInfo {
	const oracleText = getOracleText(card).toLowerCase();
	const typeLine = getTypeLine(card).toLowerCase();
	const keywords = card.keywords?.map((k) => k.toLowerCase()) ?? [];

	// Check for "Partner with [Name]" pattern - extract the name
	const partnerWithMatch = oracleText.match(/partner with ([^(]+)\s*\(/i);
	const partnerWithName = partnerWithMatch ? partnerWithMatch[1].trim() : null;

	// Friends forever uses "Partner—Friends forever" syntax
	// Scryfall keyword array just shows "Partner", so we check oracle text
	const hasFriendsForever = /partner[—-]+friends forever/i.test(oracleText);

	// Generic partner has "Partner" keyword but NOT "Partner with X" or "Friends forever"
	const hasPartnerKeyword = keywords.includes("partner");
	const hasGenericPartner =
		hasPartnerKeyword && !partnerWithName && !hasFriendsForever;

	return {
		hasGenericPartner,
		hasFriendsForever,
		partnerWithName,
		choosesBackground: oracleText.includes("choose a background"),
		isBackground: typeLine.includes("background"),
		hasDoctorsCompanion: keywords.includes("doctor's companion"),
	};
}

export function isDoctor(card: Card): boolean {
	const typeLine = getTypeLine(card).toLowerCase();
	return typeLine.includes("time lord") && typeLine.includes("doctor");
}

/**
 * Color identity - all cards must match commander's color identity
 * Errors for main deck, warnings for maybeboard
 */
export const colorIdentityRule: Rule<"colorIdentity"> = {
	id: "colorIdentity",
	rule: asRuleNumber("903.4"),
	ruleText:
		"The Commander variant uses color identity to determine what cards can be in a deck with a certain commander. The color identity of a card is the color or colors of any mana symbols in that card's mana cost or rules text, plus any colors defined by its characteristic-defining abilities (see rule 604.3) or color indicator (see rule 204).",
	category: "identity",
	description: "Cards must match commander color identity",
	validate(ctx: ValidationContext): Violation[] {
		const { deck, cardLookup, commanderColors } = ctx;

		if (!commanderColors) return [];

		const violations: Violation[] = [];
		const allowedColors = new Set<string>(commanderColors);

		for (const entry of deck.cards) {
			if (entry.section === "commander") continue;

			const card = cardLookup(entry.scryfallId);
			if (!card) continue;

			const cardIdentity = card.color_identity ?? [];
			const invalidColors = cardIdentity.filter((c) => !allowedColors.has(c));

			if (invalidColors.length > 0) {
				const commanderStr =
					commanderColors.length > 0 ? commanderColors.join("") : "colorless";
				const severity = entry.section === "maybeboard" ? "warning" : "error";

				violations.push(
					violation(
						this,
						`${card.name} has colors outside commander identity (${invalidColors.join("")} not in ${commanderStr})`,
						severity,
						{
							cardName: card.name,
							oracleId: entry.oracleId,
							section: isKnownSection(entry.section)
								? entry.section
								: undefined,
						},
					),
				);
			}
		}

		return violations;
	},
};

/**
 * Commander must be a planeswalker (Oathbreaker)
 */
export const commanderPlaneswalkerRule: Rule<"commanderPlaneswalker"> = {
	id: "commanderPlaneswalker",
	rule: asRuleNumber("906.3"),
	ruleText:
		"Each deck has a planeswalker card designated as its Oathbreaker. This designation is an attribute of the card itself. The card retains this designation even when it changes zones. (oathbreakermtg.org/rules)",
	category: "structure",
	description: "Commander must be a planeswalker (Oathbreaker)",
	validate(ctx: ValidationContext): Violation[] {
		const { deck, cardLookup } = ctx;
		const violations: Violation[] = [];
		const commanders = getCardsInSection(deck, "commander");

		for (const entry of commanders) {
			const card = cardLookup(entry.scryfallId);
			if (!card) continue;

			const typeLine = getTypeLine(card).toLowerCase();

			// Skip signature spell (instant/sorcery) - that's validated separately
			if (typeLine.includes("instant") || typeLine.includes("sorcery")) {
				continue;
			}

			if (!typeLine.includes("planeswalker")) {
				violations.push(
					violation(this, `${card.name} is not a planeswalker`, "error", {
						cardName: card.name,
						oracleId: entry.oracleId,
						section: "commander",
					}),
				);
			}
		}

		return violations;
	},
};

/**
 * Signature spell requirement (Oathbreaker)
 * Commander section must have exactly one instant or sorcery
 * Signature spell must match oathbreaker's color identity
 */
export const signatureSpellRule: Rule<"signatureSpell"> = {
	id: "signatureSpell",
	rule: asRuleNumber("906.4"),
	ruleText:
		"Each deck has an instant or sorcery card designated as its Signature Spell. The Signature Spell must fall within the color identity of the Oathbreaker. (oathbreakermtg.org/rules)",
	category: "structure",
	description:
		"Oathbreaker requires exactly one signature spell (instant/sorcery) within color identity",
	validate(ctx: ValidationContext): Violation[] {
		const { deck, cardLookup, commanderColors } = ctx;
		const commanders = getCardsInSection(deck, "commander");
		const violations: Violation[] = [];

		let signatureSpellCount = 0;
		const allowedColors = new Set<string>(commanderColors ?? []);

		for (const entry of commanders) {
			const card = cardLookup(entry.scryfallId);
			if (!card) continue;

			const typeLine = getTypeLine(card).toLowerCase();
			if (typeLine.includes("instant") || typeLine.includes("sorcery")) {
				signatureSpellCount += entry.quantity;

				if (commanderColors) {
					const spellIdentity = card.color_identity ?? [];
					const invalidColors = spellIdentity.filter(
						(c) => !allowedColors.has(c),
					);
					if (invalidColors.length > 0) {
						const commanderStr =
							commanderColors.length > 0
								? commanderColors.join("")
								: "colorless";
						violations.push(
							violation(
								this,
								`Signature spell ${card.name} has colors outside oathbreaker color identity (${invalidColors.join("")} not in ${commanderStr})`,
								"error",
								{
									cardName: card.name,
									oracleId: entry.oracleId,
									section: "commander",
								},
							),
						);
					}
				}
			}
		}

		if (signatureSpellCount === 0) {
			violations.push(
				violation(
					this,
					"Oathbreaker deck must have a signature spell (instant/sorcery in commander zone)",
					"error",
				),
			);
			return violations;
		}

		if (signatureSpellCount > 1) {
			violations.push(
				violation(
					this,
					`Oathbreaker deck can only have 1 signature spell, found ${signatureSpellCount}`,
					"error",
				),
			);
		}

		return violations;
	},
};