/**
 * Sema invariants validator.
 *
 * Sema es autónoma. Los invariantes internos (nombres únicos, eventos
 * canónicos) se validan sin morfo. Cuando se pasa morfo como contexto
 * opcional, se añaden los cross-checks (parts, data[], states[],
 * data-last-action.values[]).
 *
 * El validador recibe el morfo por su **forma estructural** (el tipo
 * `MorfoContext` de abajo), no por su tipo `Morfo`. Así sema sigue sin
 * depender del módulo morfo a nivel de tipos: cualquier valor que tenga
 * `kebab` + `parts` servirá. En la práctica el llamador pasa un `Morfo`
 * y TypeScript lo acepta por compatibilidad estructural.
 *
 * Importante: `validateSema()` asume que el `spec` ya está tipado por
 * TypeScript (`as const satisfies SemaSpec`). A diferencia de
 * `validateMorfo()`, no hace decode completo del shape runtime; valida
 * invariantes semánticos y referencias cruzadas sobre entrada tipada.
 */

import type { SemaSpec, SemaEventLabel } from './types';

// Estructura mínima que el validador necesita del morfo para hacer los
// cross-checks. Redeclarada aquí (no importada de morfo) para que sema
// no tenga dependencia de tipos con morfo.
interface MorfoPartLike {
	kebab: string;
	states?: readonly string[];
	data: readonly { attr: string; values?: readonly string[] }[];
	parts?: readonly MorfoPartLike[];
}

interface MorfoContext {
	kebab: string;
	parts: readonly MorfoPartLike[];
}

/** Thrown when a sema invariant fails. */
export class SemaInvariantError extends Error {
	constructor(message: string) {
		super(message);
		this.name = 'SemaInvariantError';
	}
}

/** Los 22 eventos canónicos. Debe mantenerse en sync con `SemaEventLabel`. */
const SEMA_EVENT_LABELS = new Set<SemaEventLabel>([
	'contact-neutral',
	'contact-threat',
	'contact-risk',
	'contact-affirm',
	'contact-fulfill',
	'commit-neutral',
	'commit-threat',
	'commit-risk',
	'commit-affirm',
	'commit-fulfill',
	'alert-neutral',
	'alert-threat',
	'alert-risk',
	'alert-affirm',
	'alert-fulfill',
	'handle-neutral',
	'handle-threat',
	'handle-risk',
	'handle-affirm',
	'handle-fulfill',
	'emerge',
	'sustain'
]);

function flattenParts(parts: readonly MorfoPartLike[]): MorfoPartLike[] {
	const out: MorfoPartLike[] = [];
	for (const p of parts) {
		out.push(p);
		if (p.parts && p.parts.length > 0) out.push(...flattenParts(p.parts));
	}
	return out;
}

/**
 * Valida los invariantes de un `SemaSpec`.
 *
 * **Invariantes internos** (siempre):
 *  1. `name` único dentro del spec.
 *  2. `event` pertenece al vocabulario canónico.
 *
 * **Invariantes cross-morfo** (sólo si se pasa `morfo`):
 *  3. `spec.kebab === morfo.kebab`.
 *  4. `action.target.target` resuelve a una parte del morfo.
 *  5. `prewrite[].part.target` resuelve.
 *  6. `prewrite[].attr` existe en `data[]` del part destino.
 *  7. `prewrite[].value` ∈ `values[]` si el attr es enumerable.
 *  8. `commits.part.target` resuelve.
 *  9. `commits.value` ∈ `states[]` si `commits.attr === 'data-state'`.
 * 10. `data-last-action.values[]` == unión de prewrites que escriben a ese
 *     attr (ambas direcciones).
 * 11. `sustains[].target.target` y `sustains[].activeWhen.part.target` resuelven.
 */
export function validateSema(spec: SemaSpec, morfo?: MorfoContext): void {
	// 1. Nombres únicos (siempre).
	const actionNames = new Set<string>();
	for (const action of spec.actions) {
		if (actionNames.has(action.name)) {
			throw new SemaInvariantError(
				`sema: duplicate action name "${action.name}" in "${spec.kebab}"`
			);
		}
		actionNames.add(action.name);
	}

	// 2. Eventos canónicos (siempre).
	for (const action of spec.actions) {
		if (!SEMA_EVENT_LABELS.has(action.event)) {
			throw new SemaInvariantError(
				`sema.actions["${action.name}"]: event "${action.event}" is not a valid SemaEventLabel`
			);
		}
	}

	// Resto depende de tener contexto de morfo.
	if (!morfo) return;

	// 3. kebab coincide.
	if (morfo.kebab !== spec.kebab) {
		throw new SemaInvariantError(
			`sema: spec.kebab "${spec.kebab}" does not match morfo.kebab "${morfo.kebab}"`
		);
	}

	const flat = flattenParts(morfo.parts);
	const kebabs = new Set<string>();
	const partByKebab = new Map<string, MorfoPartLike>();
	for (const part of flat) {
		kebabs.add(part.kebab);
		partByKebab.set(part.kebab, part);
	}

	const prewriteDLAByPart = new Map<string, Set<string>>();

	for (const action of spec.actions) {
		const ctx = `sema.actions["${action.name}"]`;

		// 4. target.
		if (!kebabs.has(action.target.target)) {
			throw new SemaInvariantError(
				`${ctx}: target "${action.target.target}" does not match any part in "${morfo.kebab}"`
			);
		}

		// 5-7. prewrites.
		for (const pw of action.prewrite ?? []) {
			const pwCtx = `${ctx}.prewrite[${pw.attr}]`;
			if (!kebabs.has(pw.part.target)) {
				throw new SemaInvariantError(
					`${pwCtx}: part "${pw.part.target}" does not match any part in "${morfo.kebab}"`
				);
			}
			const targetPart = partByKebab.get(pw.part.target);
			if (!targetPart) continue;
			const dataEntry = targetPart.data.find((d) => d.attr === pw.attr);
			if (!dataEntry) {
				throw new SemaInvariantError(
					`${pwCtx}: attr "${pw.attr}" not declared in part "${pw.part.target}"'s data[] (declare it before referencing)`
				);
			}
			if (dataEntry.values && !dataEntry.values.includes(pw.value)) {
				throw new SemaInvariantError(
					`${pwCtx}: value "${pw.value}" not in declared values [${dataEntry.values.join(', ')}]`
				);
			}
			if (pw.attr === 'data-last-action') {
				const s = prewriteDLAByPart.get(pw.part.target) ?? new Set<string>();
				s.add(pw.value);
				prewriteDLAByPart.set(pw.part.target, s);
			}
		}

		// 8-9. commits.
		if (action.commits) {
			const cCtx = `${ctx}.commits`;
			if (!kebabs.has(action.commits.part.target)) {
				throw new SemaInvariantError(
					`${cCtx}: part "${action.commits.part.target}" does not match any part in "${morfo.kebab}"`
				);
			}
			if (action.commits.attr === 'data-state') {
				const targetPart = partByKebab.get(action.commits.part.target);
				const states = targetPart?.states ?? [];
				if (!states.includes(action.commits.value)) {
					throw new SemaInvariantError(
						`${cCtx}: value "${action.commits.value}" not in states of "${action.commits.part.target}" (declared: ${states.join(', ') || '∅'})`
					);
				}
			}
		}
	}

	// 10. data-last-action.values[] == unión de prewrites que lo escriben.
	for (const part of flat) {
		const partKebab = part.kebab;
		const dla = part.data.find((d) => d.attr === 'data-last-action');
		if (!dla?.values) continue;
		const written = prewriteDLAByPart.get(partKebab) ?? new Set<string>();
		const declared = new Set(dla.values);
		for (const v of written) {
			if (!declared.has(v)) {
				throw new SemaInvariantError(
					`sema: prewrite writes "${v}" to data-last-action on "${partKebab}", but the part's values[] does not include it (declared: ${[...declared].join(', ')})`
				);
			}
		}
		for (const v of declared) {
			if (!written.has(v)) {
				throw new SemaInvariantError(
					`sema: part "${partKebab}" declares data-last-action value "${v}" but no sema action prewrites it — values[] must equal the union of prewrites`
				);
			}
		}
	}

	// 11. sustains.
	for (const sustain of spec.sustains ?? []) {
		const ctx = `sema.sustains["${sustain.name}"]`;
		if (!kebabs.has(sustain.target.target)) {
			throw new SemaInvariantError(
				`${ctx}: target "${sustain.target.target}" does not match any part`
			);
		}
		if (!kebabs.has(sustain.activeWhen.part.target)) {
			throw new SemaInvariantError(
				`${ctx}: activeWhen.part "${sustain.activeWhen.part.target}" does not match any part`
			);
		}
	}
}