initiative/packages/domain/src/toggle-condition.ts

import type { ConditionEntry, ConditionId } from "./conditions.js";
import { CONDITION_DEFINITIONS, VALID_CONDITION_IDS } from "./conditions.js";
import type { DomainEvent } from "./events.js";
import {
	type CombatantId,
	type DomainError,
	type Encounter,
	findCombatant,
	isDomainError,
} from "./types.js";

export interface ToggleConditionSuccess {
	readonly encounter: Encounter;
	readonly events: DomainEvent[];
}

function validateConditionId(conditionId: ConditionId): DomainError | null {
	if (!VALID_CONDITION_IDS.has(conditionId)) {
		return {
			kind: "domain-error",
			code: "unknown-condition",
			message: `Unknown condition "${conditionId}"`,
		};
	}
	return null;
}

function applyConditions(
	encounter: Encounter,
	combatantId: CombatantId,
	newConditions: readonly ConditionEntry[] | undefined,
): Encounter {
	return {
		combatants: encounter.combatants.map((c) =>
			c.id === combatantId ? { ...c, conditions: newConditions } : c,
		),
		activeIndex: encounter.activeIndex,
		roundNumber: encounter.roundNumber,
	};
}

export function toggleCondition(
	encounter: Encounter,
	combatantId: CombatantId,
	conditionId: ConditionId,
): ToggleConditionSuccess | DomainError {
	const err = validateConditionId(conditionId);
	if (err) return err;

	const found = findCombatant(encounter, combatantId);
	if (isDomainError(found)) return found;
	const { combatant: target } = found;
	const current = target.conditions ?? [];
	const isActive = current.some((c) => c.id === conditionId);

	let newConditions: readonly ConditionEntry[] | undefined;
	let event: DomainEvent;

	if (isActive) {
		const filtered = current.filter((c) => c.id !== conditionId);
		newConditions = filtered.length > 0 ? filtered : undefined;
		event = { type: "ConditionRemoved", combatantId, condition: conditionId };
	} else {
		newConditions = [...current, { id: conditionId }];
		event = { type: "ConditionAdded", combatantId, condition: conditionId };
	}

	return {
		encounter: applyConditions(encounter, combatantId, newConditions),
		events: [event],
	};
}

export function setConditionValue(
	encounter: Encounter,
	combatantId: CombatantId,
	conditionId: ConditionId,
	value: number,
): ToggleConditionSuccess | DomainError {
	const err = validateConditionId(conditionId);
	if (err) return err;

	const found = findCombatant(encounter, combatantId);
	if (isDomainError(found)) return found;
	const { combatant: target } = found;
	const current = target.conditions ?? [];

	const def = CONDITION_DEFINITIONS.find((d) => d.id === conditionId);
	const clampedValue =
		def?.maxValue === undefined ? value : Math.min(value, def.maxValue);

	if (clampedValue <= 0) {
		const filtered = current.filter((c) => c.id !== conditionId);
		const newConditions = filtered.length > 0 ? filtered : undefined;
		return {
			encounter: applyConditions(encounter, combatantId, newConditions),
			events: [
				{ type: "ConditionRemoved", combatantId, condition: conditionId },
			],
		};
	}

	const existing = current.find((c) => c.id === conditionId);
	if (existing) {
		const updated = current.map((c) =>
			c.id === conditionId ? { ...c, value: clampedValue } : c,
		);
		return {
			encounter: applyConditions(encounter, combatantId, updated),
			events: [
				{
					type: "ConditionAdded",
					combatantId,
					condition: conditionId,
					value: clampedValue,
				},
			],
		};
	}

	const added = [...current, { id: conditionId, value: clampedValue }];
	return {
		encounter: applyConditions(encounter, combatantId, added),
		events: [
			{
				type: "ConditionAdded",
				combatantId,
				condition: conditionId,
				value: clampedValue,
			},
		],
	};
}

export function decrementCondition(
	encounter: Encounter,
	combatantId: CombatantId,
	conditionId: ConditionId,
): ToggleConditionSuccess | DomainError {
	const err = validateConditionId(conditionId);
	if (err) return err;

	const found = findCombatant(encounter, combatantId);
	if (isDomainError(found)) return found;
	const { combatant: target } = found;
	const current = target.conditions ?? [];
	const existing = current.find((c) => c.id === conditionId);

	if (!existing) {
		return {
			kind: "domain-error",
			code: "condition-not-active",
			message: `Condition "${conditionId}" is not active`,
		};
	}

	const newValue = (existing.value ?? 1) - 1;
	if (newValue <= 0) {
		const filtered = current.filter((c) => c.id !== conditionId);
		return {
			encounter: applyConditions(
				encounter,
				combatantId,
				filtered.length > 0 ? filtered : undefined,
			),
			events: [
				{ type: "ConditionRemoved", combatantId, condition: conditionId },
			],
		};
	}

	const updated = current.map((c) =>
		c.id === conditionId ? { ...c, value: newValue } : c,
	);
	return {
		encounter: applyConditions(encounter, combatantId, updated),
		events: [
			{
				type: "ConditionAdded",
				combatantId,
				condition: conditionId,
				value: newValue,
			},
		],
	};
}