/**
 * checks/registry.ts — pluggable check registry.
 *
 * A `CheckDefinition` describes one hygiene check (e.g. `comments`, `complexity`).
 * The registry is a module-level `Map` so that adding a check only requires a
 * new file in `src/checks/` plus one `registerCheck(def)` call — no changes to
 * `index.ts` command wiring. At startup, `index.ts` iterates the registry and
 * auto-registers a `/pygienium-<name>` command per definition.
 *
 * Lifecycle of a single check run (orchestrated by `src/modes/check-runner.ts`):
 *   Q0 recon (shared) → analysis sub-agent (buildScanTask) →
 *   fix sub-agent (buildFixTask, only with --fix) → verify gate → cleanup.
 *
 * @module pygienium/checks/registry
 */

/**
 * Scope passed to scan/fix task builders. Resolved from the command args:
 * a positional path (absolute or relative to `cwd`) plus parsed flags.
 */
export interface CheckScope {
	/** Absolute working directory the check operates on. */
	cwd: string;
	/** Target path (absolute) the check scans; defaults to `cwd` when none given. */
	target: string;
	/** Whether fixes should be applied (the `--fix` flag). */
	fix: boolean;
	/** Remaining raw tokens after flag parsing, for check-specific use. */
	rest: string[];
}

/**
 * Verifies preconditions before a check runs its analysis phase. Returns an
 * error string when the check cannot proceed (e.g. no source files match),
 * or `undefined` when the gate passes. Implemented per-check so generic
 * checks can bail early without spawning an agent.
 */
export type CheckGate = (
	cwd: string,
) => Promise<string | undefined> | string | undefined;

/**
 * Optional post-analysis (+ optional fix) verify hook. Confirms the check
 * actually produced its artifacts (e.g. `findings.md`/`changes.md`). Returns an
 * error string to fail the verify phase, or `undefined` to pass. When omitted,
 * the verify phase falls back to re-running {@link CheckDefinition.gate},
 * preserving the historical behaviour for checks that have nothing to verify.
 */
export type CheckVerify = (
	scope: CheckScope,
) => Promise<string | undefined> | string | undefined;

/**
 * The structured task string handed to a sub-agent. `buildScanTask` produces
 * the analysis prompt; `buildFixTask` consumes the findings text the scan
 * agent emitted and produces a fix prompt.
 *
 * Task builders may be async: a check can pre-compute deterministic candidates
 * (e.g. an import-graph scan) before assembling the prompt, so the sub-agent's
 * job is to verify/refine rather than re-derive everything from scratch.
 */
export type BuildScanTask = (
	cwd: string,
	scope: CheckScope,
) => string | Promise<string>;
export type BuildFixTask = (
	cwd: string,
	scope: CheckScope,
	findings: string,
) => string | Promise<string>;

/**
 * Definition of a single pluggable hygiene check.
 */
export interface CheckDefinition {
	/** Lowercase kebab command suffix → `/pygienium-<name>`. Must be unique. */
	name: string;
	/** Human label shown in help and status strips. */
	label: string;
	/** One-line description for `/pygienium-help`. */
	description: string;
	/**
	 * Name of the agent definition (from `agents/*.md`) used for the analysis
	 * phase. The fix phase uses the `fixer` agent unless `fixAgentName`
	 * overrides it.
	 */
	agentName: string;
	/** Optional override for the fix-phase agent (defaults to `fixer`). */
	fixAgentName?: string;
	/** Identifier of the phase-strip phase this check belongs to (task 05). */
	phaseId: string;
	/** Builds the analysis sub-agent task. */
	buildScanTask: BuildScanTask;
	/** Builds the fix sub-agent task from scan findings. */
	buildFixTask: BuildFixTask;
	/**
	 * Precondition gate. Returning a string skips the check (recorded as
	 * `skipped`); returning `undefined` proceeds normally.
	 */
	gate: CheckGate;
	/**
	 * Optional verify hook confirming artifacts landed (see {@link CheckVerify}).
	 * Falls back to re-running `gate` when omitted.
	 */
	verify?: CheckVerify;
}

const registry = new Map<string, CheckDefinition>();

/**
 * Register a check. Throws on duplicate names so wiring mistakes surface
 * loudly at startup rather than silently shadowing a command.
 */
export function registerCheck(def: CheckDefinition): void {
	if (!def.name || !/^[a-z0-9][a-z0-9-]*$/.test(def.name)) {
		throw new Error(
			`Invalid check name "${def.name}": must be lowercase kebab (e.g. "comments").`,
		);
	}
	if (registry.has(def.name)) {
		throw new Error(`Duplicate pygienium check name: "${def.name}".`);
	}
	registry.set(def.name, def);
}

/** Look up a registered check by name. */
export function getCheck(name: string): CheckDefinition | undefined {
	return registry.get(name);
}

/** All registered checks in insertion order. */
export function getAllChecks(): CheckDefinition[] {
	return [...registry.values()];
}

/** Test-only: reset the registry between tests. */
export function clearChecks(): void {
	registry.clear();
}