import type { DomainEvent } from "./events.js";
import type {
	PlayerCharacter,
	PlayerCharacterId,
} from "./player-character-types.js";
import {
	VALID_PLAYER_COLORS,
	VALID_PLAYER_ICONS,
} from "./player-character-types.js";
import type { DomainError } from "./types.js";

export interface EditPlayerCharacterSuccess {
	readonly characters: readonly PlayerCharacter[];
	readonly events: DomainEvent[];
}

interface EditFields {
	readonly name?: string;
	readonly ac?: number;
	readonly maxHp?: number;
	readonly color?: string;
	readonly icon?: string;
}

function validateFields(fields: EditFields): DomainError | null {
	if (fields.name !== undefined && fields.name.trim() === "") {
		return {
			kind: "domain-error",
			code: "invalid-name",
			message: "Player character name must not be empty",
		};
	}
	if (
		fields.ac !== undefined &&
		(!Number.isInteger(fields.ac) || fields.ac < 0)
	) {
		return {
			kind: "domain-error",
			code: "invalid-ac",
			message: "AC must be a non-negative integer",
		};
	}
	if (
		fields.maxHp !== undefined &&
		(!Number.isInteger(fields.maxHp) || fields.maxHp < 1)
	) {
		return {
			kind: "domain-error",
			code: "invalid-max-hp",
			message: "Max HP must be a positive integer",
		};
	}
	if (fields.color !== undefined && !VALID_PLAYER_COLORS.has(fields.color)) {
		return {
			kind: "domain-error",
			code: "invalid-color",
			message: `Invalid color: ${fields.color}`,
		};
	}
	if (fields.icon !== undefined && !VALID_PLAYER_ICONS.has(fields.icon)) {
		return {
			kind: "domain-error",
			code: "invalid-icon",
			message: `Invalid icon: ${fields.icon}`,
		};
	}
	return null;
}

function applyFields(
	existing: PlayerCharacter,
	fields: EditFields,
): PlayerCharacter {
	return {
		id: existing.id,
		name: fields.name !== undefined ? fields.name.trim() : existing.name,
		ac: fields.ac !== undefined ? fields.ac : existing.ac,
		maxHp: fields.maxHp !== undefined ? fields.maxHp : existing.maxHp,
		color:
			fields.color !== undefined
				? (fields.color as PlayerCharacter["color"])
				: existing.color,
		icon:
			fields.icon !== undefined
				? (fields.icon as PlayerCharacter["icon"])
				: existing.icon,
	};
}

export function editPlayerCharacter(
	characters: readonly PlayerCharacter[],
	id: PlayerCharacterId,
	fields: EditFields,
): EditPlayerCharacterSuccess | DomainError {
	const index = characters.findIndex((c) => c.id === id);
	if (index === -1) {
		return {
			kind: "domain-error",
			code: "player-character-not-found",
			message: `Player character not found: ${id}`,
		};
	}

	const validationError = validateFields(fields);
	if (validationError) return validationError;

	const existing = characters[index];
	const updated = applyFields(existing, fields);

	if (
		updated.name === existing.name &&
		updated.ac === existing.ac &&
		updated.maxHp === existing.maxHp &&
		updated.color === existing.color &&
		updated.icon === existing.icon
	) {
		return {
			kind: "domain-error",
			code: "no-changes",
			message: "No fields changed",
		};
	}

	const newList = characters.map((c, i) => (i === index ? updated : c));

	return {
		characters: newList,
		events: [
			{
				type: "PlayerCharacterUpdated",
				playerCharacterId: id,
				oldName: existing.name,
				newName: updated.name,
			},
		],
	};
}