/**
 * installed-surface-resolver.cts — Installed Surface Resolver Module (#2872,
 * ADR-2866, Phase 3 — governed by
 * `.gsd/phase/feat-2872-manifest-scope-runtime/40-design.md`).
 *
 * `resolveInstalledSurfaces(runtime?, opts?)` answers a question no existing
 * module answers: "which surfaces actually exist on THIS machine, across
 * BOTH install scopes, right now?" `capability-state.cts` answers "which
 * capabilities are enabled in THIS config dir" — a different question at a
 * different altitude. This module is a new leaf: it reads two scopes at
 * once, composing three already-shipped, already-tested pieces
 * (`resolveScope`, Phase 1; `resolveTriggerSurface`, Phase 2; and
 * `readInstallManifest`, widened in this same phase) rather than
 * re-implementing any of their rules.
 *
 * ── Probe-not-declared keying ───────────────────────────────────────────────
 * A scope RECORD is keyed by the PROBED scope (`resolveScope`'s own `id`),
 * never by what the manifest itself claims. `manifestVersion`/`runtime`/
 * `scope` recorded inside a v2 manifest are corroboration, not identity: a
 * manifest copied between config dirs, or a `--config-dir` install, must
 * still be reported at the scope this machine actually resolves to.
 *
 * ── Report, don't correct ───────────────────────────────────────────────────
 * When a declared `runtime`/`scope` disagrees with the probe, this module
 * reports the mismatch (`declaredScopeMatchesProbe: false` /
 * `declaredRuntimeMatchesProbe: false`) and otherwise proceeds exactly as it
 * would for an undeclared (v1) manifest. It never silently substitutes the
 * declared value for the probed one, and never throws on a mismatch — see
 * B-row "Postel's Law" discussion in the design doc.
 *
 * ── One trigger call over installed scopes only ─────────────────────────────
 * `resolveTriggerSurface` is called AT MOST once per runtime, with the
 * scopes that are actually installed on this machine (per manifest
 * presence — never per the new corroboration fields, which is what keeps a
 * v1-only install fully functional with no reinstall required). A
 * hypothetical "what if both scopes were installed" answer is deliberately
 * not offered; #2218 is a fact about THIS machine, not a simulation.
 *
 * ── Installed-ness is manifest PRESENCE, never the new fields ───────────────
 * `installed` is `manifestVersion !== null`. A v1 manifest (no
 * `manifestVersion` key at all, `manifestVersion: 1` after normalization) is
 * a correct manifest written by an older GSD — never a broken one, never
 * grounds for `installed: false`, a warning, or a reinstall prompt.
 *
 * ── Stems come from the manifest, not the source tree ───────────────────────
 * `resolveTriggerSurface` needs `stems`. They are derived from the
 * INSTALLED manifest's own `files` keys (see the private stem-derivation
 * helpers below), never from a roster read of the source tree — a global
 * `claude` install ships no `commands/gsd` source, so a roster read would
 * return `[]` in exactly the configuration #2218 is about. The derivation
 * consumes `isNamespacedByDir` and `composeCommandFilename`
 * (`runtime-artifact-layout.cjs`, #2871 Phase 2's exported helpers) rather
 * than re-deriving either rule as a fourth independent copy.
 */

import fs from 'node:fs';
import path from 'node:path';
import { resolveScope, SCOPE_ORDER, type InstallScope } from './install-scope.cjs';
import { posixNormalize } from './shell-command-projection.cjs';

// eslint-disable-next-line @typescript-eslint/no-require-imports
import runtimeArtifactLayoutMod = require('./runtime-artifact-layout.cjs');
const {
  resolveRuntimeArtifactLayout,
  resolveRuntimeArtifactLayoutFromRegistry,
  resolveTriggerSurface,
  isNamespacedByDir,
  composeCommandFilename,
} = runtimeArtifactLayoutMod;

// eslint-disable-next-line @typescript-eslint/no-require-imports
import installerMigrationsMod = require('./installer-migrations.cjs');
const { readInstallManifest, MANIFEST_NAME } = installerMigrationsMod;

// In .cts (CommonJS output) files, `require` is available as a global.
const _require: NodeRequire = require;

// ── Types derived from the two composed modules ────────────────────────────
//
// Neither `TriggerSurface` nor the two modules' private registry shapes are
// exported by name from `runtime-artifact-layout.cts` (only the functions
// are, via its `export =`). Deriving the types with `ReturnType`/
// `Parameters` off the imported function values — rather than duplicating
// the shapes here as a second, driftable copy — is the same pattern already
// used elsewhere in this codebase (e.g. `phase.cts`, `config.cts`).

/** One resolved `/gsd-<name>`-style trigger, as `resolveTriggerSurface`
 *  (`runtime-artifact-layout.cts`, #2871 Phase 2) produces it. */
type TriggerSurface = ReturnType<typeof resolveTriggerSurface>[number];

/** The registry shape `resolveRuntimeArtifactLayoutFromRegistry` accepts as
 *  its first argument — reused so `opts.registry` can be forwarded to it
 *  without a second, independently-typed registry shape. */
type LayoutRegistryLike = Parameters<typeof resolveRuntimeArtifactLayoutFromRegistry>[0];

/** The registry shape `resolveTriggerSurface`'s `opts.registry` accepts. */
type TriggerRegistryLike = NonNullable<Parameters<typeof resolveTriggerSurface>[2]['registry']>;

/** Minimal shape this module needs to enumerate registered runtime ids
 *  (C7) — deliberately narrower than `LayoutRegistryLike`/`TriggerRegistryLike`
 *  above (`Object.keys` needs nothing more than the `runtimes` map itself). */
interface RuntimeEnumerableRegistry {
  runtimes: Record<string, unknown>;
}

// ── Public types ────────────────────────────────────────────────────────

export interface InstalledScopeRecord {
  scope: InstallScope;
  configHome: string;
  installed: boolean;
  manifestVersion: number | null;
  declaredRuntime: string | null;
  declaredScope: InstallScope | null;
  /** `null` when nothing was declared (v1 manifest or not installed). */
  declaredScopeMatchesProbe: boolean | null;
  declaredRuntimeMatchesProbe: boolean | null;
  /** Trigger stems derived from this scope's manifest keys, sorted, deduped. */
  stems: string[];
}

export interface InstalledRuntimeSurface {
  runtime: string;
  scopes: InstalledScopeRecord[];
  /** Resolved across ONLY the installed scopes, in one resolveTriggerSurface
   *  call, so `shadowedBy` describes THIS machine rather than a hypothetical. */
  triggers: TriggerSurface[];
}

export interface ResolveInstalledSurfacesOptions {
  home?: string;
  cwd?: string;
  env?: Record<string, string | undefined>;
  existsSync?: (p: string) => boolean;
  /** Injected for tests, matching `existsSync` above; defaults to
   *  `node:fs`'s `lstatSync`. Used to refuse a manifest read when the
   *  scope's config dir or manifest file is a symlink — see the
   *  `buildScopeRecord` comment for why this is a deliberate hardening,
   *  not an oversight. */
  lstatSync?: (p: string) => { isSymbolicLink(): boolean };
  registry?: unknown;
  /** Injected for tests; defaults to installer-migrations' readInstallManifest. */
  readManifest?: (configDir: string) => {
    manifestVersion: number | null;
    runtime: string | null;
    scope: InstallScope | null;
    files: Record<string, string>;
  };
}

// ── Internals ───────────────────────────────────────────────────────────

/**
 * A trigger stem is a kebab-case token and nothing else. Verified against the
 * real roster: all 71 `commands/gsd/*.md` stems match this, so it has no false
 * negatives today.
 *
 * This is a SECURITY boundary, not cosmetics. A stem is derived from a manifest
 * key — attacker-influenceable text, since a project-local
 * `gsd-file-manifest.json` lives inside a repository a user may merely have
 * cloned — and Phase 4 (#2873) renders it back to the user as `/gsd-<stem>`.
 * Without this, `skills/gsd-../../../x` yields the stem `..`, and control
 * characters, newlines, ANSI escapes and RTL-override codepoints all survive
 * into that rendered trigger. The `commands` branch happened to be protected by
 * its `composeCommandFilename` round-trip; the `skills` branch had no
 * equivalent, so the rule is stated once here and applied to both.
 */
const SAFE_STEM = /^[a-z0-9][a-z0-9-]*$/;

function getDefaultRuntimeRegistry(): RuntimeEnumerableRegistry {
  return _require('./capability-registry.cjs') as RuntimeEnumerableRegistry;
}

/** C7: every registered runtime id, sorted for determinism. Reads
 *  `opts.registry` when provided (so a sweep is assertable without the real
 *  capability registry), else the real one. */
function listRegisteredRuntimeIds(opts: ResolveInstalledSurfacesOptions): string[] {
  const registry = (opts.registry as RuntimeEnumerableRegistry | undefined) ?? getDefaultRuntimeRegistry();
  return Object.keys(registry.runtimes).sort();
}

/**
 * D — the stem inverse for one `commands`/`skills` layout kind entry.
 * Consumes `isNamespacedByDir` (to decide the commands filename shape) and
 * `composeCommandFilename` (to VERIFY a candidate stem round-trips to the
 * exact filename seen) rather than re-deriving either rule locally (design
 * "Rejected" #6). Manifest keys are normalized with an unconditional
 * `.replace(/\\/g, '/')` (D7) — never gated on `path.sep` — matching this
 * repo's recorded path-separator-normalization defect class.
 */
function deriveStemsForKindEntry(
  kind: 'commands' | 'skills',
  destSubpath: string,
  prefix: string,
  fileKeys: readonly string[],
): string[] {
  const destSubpathNorm = posixNormalize(destSubpath);
  const boundary = `${destSubpathNorm}/`;
  const namespacedByDir = isNamespacedByDir(kind, destSubpath, prefix);
  const stems = new Set<string>();

  for (const rawKey of fileKeys) {
    const key = rawKey.replace(/\\/g, '/');
    if (!key.startsWith(boundary)) continue; // D4: key not under this declared subpath
    const rest = key.slice(boundary.length);
    if (rest === '') continue;
    const segments = rest.split('/');

    if (kind === 'skills') {
      const dirSegment = segments[0];
      if (!dirSegment.startsWith(prefix)) continue; // D5: subpath matches, prefix does not
      const stem = dirSegment.slice(prefix.length);
      if (stem === '') continue; // D7/B7: empty stem never emitted
      if (!SAFE_STEM.test(stem)) continue; // security: reject anything but a kebab-case token
      stems.add(stem); // D6: several files under one dir -> one stem
      continue;
    }

    // commands: exactly one path segment — the composed filename itself.
    if (segments.length !== 1) continue;
    const filename = segments[0];
    if (!filename.endsWith('.md')) continue;
    const base = filename.slice(0, -3);
    const candidateStem = namespacedByDir
      ? base
      : (base.startsWith(prefix) ? base.slice(prefix.length) : '');
    if (candidateStem === '') continue;
    if (composeCommandFilename(namespacedByDir, prefix, candidateStem) !== filename) continue;
    if (!SAFE_STEM.test(candidateStem)) continue; // security: reject anything but a kebab-case token
    stems.add(candidateStem);
  }

  return [...stems];
}

/** D — full stem set for one scope: every `commands`/`skills` layout kind
 *  entry, unioned. Empty `files` (C13) short-circuits to `[]` without
 *  resolving a layout at all. */
function deriveStemsFromManifest(
  runtime: string,
  scopeId: InstallScope,
  configHome: string,
  files: Record<string, string>,
  opts: ResolveInstalledSurfacesOptions,
): string[] {
  const fileKeys = Object.keys(files);
  if (fileKeys.length === 0) return [];

  const layout = opts.registry !== undefined
    ? resolveRuntimeArtifactLayoutFromRegistry(opts.registry as LayoutRegistryLike, runtime, configHome, scopeId)
    : resolveRuntimeArtifactLayout(runtime, configHome, scopeId);

  const stems = new Set<string>();
  for (const kindEntry of layout.kinds) {
    if (kindEntry.kind !== 'commands' && kindEntry.kind !== 'skills') continue; // excludes agents/kimi-agents (D4)
    for (const stem of deriveStemsForKindEntry(kindEntry.kind, kindEntry.destSubpath, kindEntry.prefix, fileKeys)) {
      stems.add(stem);
    }
  }
  return [...stems].sort();
}

/**
 * True when `p` is a symlink. An `lstatSync` throw (ENOENT — nothing at this
 * path) is NOT evidence of a symlink; it is treated as "not a symlink" here
 * and left for `readManifest` to classify (it already owns the absent-file
 * case, per C14 above).
 */
function isSymlinkPath(p: string, lstatSync: (p: string) => { isSymbolicLink(): boolean }): boolean {
  try {
    return lstatSync(p).isSymbolicLink();
  } catch {
    return false;
  }
}

/**
 * The shared "not installed" degraded shape (C14's EACCES path, and this
 * phase's new symlink-guard path). A FACTORY, not a module-level constant
 * object: a `const` object spread at each return site would still share the
 * same `stems` ARRAY reference across every call (`...` shallow-copies the
 * object but not the array a property points at), which would violate this
 * module's own "builds fresh arrays/objects on every call" contract (C15) —
 * a caller mutating one degraded record's `stems` must never be visible on
 * another's.
 */
function notInstalledScopeRecordFields(): Pick<
  InstalledScopeRecord,
  'installed' | 'manifestVersion' | 'declaredRuntime' | 'declaredScope' | 'declaredScopeMatchesProbe' | 'declaredRuntimeMatchesProbe' | 'stems'
> {
  return {
    installed: false,
    manifestVersion: null,
    declaredRuntime: null,
    declaredScope: null,
    declaredScopeMatchesProbe: null,
    declaredRuntimeMatchesProbe: null,
    stems: [],
  };
}

/**
 * Build one scope's record. `resolvedConfigHome` has already been probed
 * successfully by the time this is called (a `resolveScope` `TypeError` is
 * handled by the caller, per C8 — it is never this function's concern).
 *
 * Two distinct failure modes are handled with two distinct, narrowly-scoped
 * try/catches — NOT one catch-all around the whole function:
 *
 *  - The manifest READ (`readManifest`) is the only thing that can justify
 *    `installed: false` (C14, e.g. EACCES). A failure here means "we could
 *    not even tell whether this scope is installed".
 *  - The stem DERIVATION (`deriveStemsFromManifest`, which resolves a
 *    runtime artifact layout) is a separate concern. A `TypeError` thrown
 *    while deriving stems is a layout-lookup failure, not evidence the
 *    manifest is absent — the manifest was already read successfully, so
 *    `installed` and every declared/*MatchesProbe field stay exactly as the
 *    manifest reported. Conflating the two would report a genuinely
 *    installed runtime as `installed: false`, hiding a real install from
 *    #2218 shadow detection precisely when this module exists to surface it.
 */
function buildScopeRecord(
  runtime: string,
  scopeId: InstallScope,
  resolvedConfigHome: string,
  opts: ResolveInstalledSurfacesOptions,
): InstalledScopeRecord {
  // Hardening requirement 2 (#2873 design doc, "Hardening requirements
  // claimed from #2873's comment"): `readInstallManifest` -> `readJsonIfPresent`
  // uses `existsSync` + `readFileSync` and therefore FOLLOWS symlinks, and
  // this module resolves `local` against `process.cwd()` — a directory that,
  // as of this phase, becomes reachable from an arbitrary cloned repository
  // (this is the same phase that makes the local scope's manifest a first
  // read target, not merely a write target). The in-tree precedent is
  // `getAgentsDir` (`agent-install-check.cts`), which probes with
  // `fs.lstatSync(...).isDirectory()`/`.isFile()` and deliberately does not
  // follow. #2872 left this resolver's read un-guarded only because the path
  // had zero callers at the time; refusing to follow a symlinked config dir
  // or manifest here closes that asymmetry rather than carrying it forward.
  // Degrading to `installed: false` reuses the SAME shape the EACCES catch
  // below already returns — no new failure shape is introduced.
  const lstatSync = opts.lstatSync ?? fs.lstatSync;
  const manifestPath = path.join(resolvedConfigHome, MANIFEST_NAME);
  if (isSymlinkPath(resolvedConfigHome, lstatSync) || isSymlinkPath(manifestPath, lstatSync)) {
    return { scope: scopeId, configHome: resolvedConfigHome, ...notInstalledScopeRecordFields() };
  }

  let manifest: {
    manifestVersion: number | null;
    runtime: string | null;
    scope: InstallScope | null;
    files: Record<string, string>;
  };
  try {
    const readManifest = opts.readManifest ?? readInstallManifest;
    manifest = readManifest(resolvedConfigHome);
  } catch {
    // C14: manifest read/probe failure degrades to not-installed, never throws.
    // Deliberately a BARE catch, unlike the stem-derivation catch below: any
    // read failure at all (EACCES, ENOENT-after-race, a corrupt filesystem)
    // legitimately means "cannot tell whether installed" (design row C14), so
    // there is no error TYPE here that should instead propagate.
    return { scope: scopeId, configHome: resolvedConfigHome, ...notInstalledScopeRecordFields() };
  }

  const installed = manifest.manifestVersion !== null; // C9: presence, never the new fields
  const declaredRuntime = manifest.runtime;
  const declaredScope = manifest.scope;
  const declaredRuntimeMatchesProbe = declaredRuntime === null ? null : declaredRuntime === runtime;
  const declaredScopeMatchesProbe = declaredScope === null ? null : declaredScope === scopeId;

  let stems: string[] = [];
  if (installed) {
    try {
      stems = deriveStemsFromManifest(runtime, scopeId, resolvedConfigHome, manifest.files, opts);
    } catch (error) {
      if (!(error instanceof TypeError)) throw error;
      // A layout-lookup failure means "we could not enumerate this scope's
      // triggers", NOT "this scope is not installed" — the manifest read
      // already succeeded above, so `installed` and the declared fields
      // stay as reported. Conflating the two would hide a real install.
      // Anything that is not the expected `TypeError` (a genuine bug in
      // `deriveStemsFromManifest`/`resolveRuntimeArtifactLayout`) is
      // rethrown rather than silently degrading to `stems: []` — this
      // matches `resolveInstalledSurfaces`'s own `TypeError` narrowing
      // below, so the two catches cannot drift apart.
      stems = [];
    }
  }

  return {
    scope: scopeId,
    configHome: resolvedConfigHome,
    installed,
    manifestVersion: manifest.manifestVersion,
    declaredRuntime,
    declaredScope,
    declaredScopeMatchesProbe,
    declaredRuntimeMatchesProbe,
    stems,
  };
}

/**
 * Resolve one runtime's full installed surface. A `resolveScope` `TypeError`
 * (unknown runtime, or `configHome.kind === 'none'`, e.g. vscode) propagates
 * from here uncaught — `resolveInstalledSurfaces` decides whether that
 * means "skip" (C7 sweep) or "propagate" (explicit single-runtime ask, C8).
 */
function resolveOneRuntime(runtime: string, opts: ResolveInstalledSurfacesOptions): InstalledRuntimeSurface {
  const scopes: InstalledScopeRecord[] = SCOPE_ORDER.map((scopeId) => {
    const resolved = resolveScope({
      id: scopeId,
      runtime,
      env: opts.env,
      home: opts.home,
      existsSync: opts.existsSync,
      cwd: opts.cwd,
    });
    return buildScopeRecord(runtime, scopeId, resolved.configHome, opts);
  });

  // C12: dedupe by resolved configHome BEFORE the trigger call, keeping the
  // higher-ranked (global, first in SCOPE_ORDER) scope. Both scope RECORDS
  // above are unaffected — only the scope list handed to resolveTriggerSurface
  // is deduped.
  const seenConfigHomes = new Set<string>();
  const triggerScopeIds: InstallScope[] = [];
  for (const record of scopes) {
    if (!record.installed) continue;
    if (seenConfigHomes.has(record.configHome)) continue;
    seenConfigHomes.add(record.configHome);
    triggerScopeIds.push(record.scope);
  }

  const stemUnion = new Set<string>();
  for (const scopeId of triggerScopeIds) {
    const record = scopes.find((s) => s.scope === scopeId);
    for (const stem of record?.stems ?? []) stemUnion.add(stem);
  }

  const triggers: TriggerSurface[] = triggerScopeIds.length > 0
    ? resolveTriggerSurface(runtime, triggerScopeIds, {
      stems: [...stemUnion].sort(),
      registry: opts.registry as TriggerRegistryLike | undefined,
    })
    : [];

  return { runtime, scopes, triggers };
}

/**
 * Read-only. Probes both install scopes for a runtime (or every registered
 * runtime, sorted by id, when `runtime` is omitted), reads each scope's
 * manifest, and resolves the trigger surface across the scopes that are
 * actually installed on this machine. See the module-level comment for the
 * non-obvious choices (probe-not-declared keying, report-don't-correct, one
 * trigger call over installed scopes only).
 *
 * Pure with respect to caller-visible state: builds fresh arrays/objects on
 * every call (C15) and performs no writes. Filesystem reads happen only via
 * `resolveScope`'s injected `existsSync`/`env`/`home`/`cwd` and via
 * `readManifest` (default: `readInstallManifest`).
 *
 * @throws {TypeError} when `runtime` is given explicitly and it is unknown,
 *   or has no installable config directory (`configHome.kind === 'none'`,
 *   e.g. vscode) — same contract `resolveScope` throws. In the all-runtimes
 *   sweep (`runtime` omitted), a runtime that would throw this same
 *   `TypeError` is skipped instead, so one non-installable runtime cannot
 *   kill the sweep (C7/C8). Any other error type is never swallowed here.
 */
export function resolveInstalledSurfaces(
  runtime?: string,
  opts: ResolveInstalledSurfacesOptions = {},
): InstalledRuntimeSurface[] {
  if (typeof runtime === 'string') {
    return [resolveOneRuntime(runtime, opts)];
  }

  const results: InstalledRuntimeSurface[] = [];
  for (const runtimeId of listRegisteredRuntimeIds(opts)) {
    try {
      results.push(resolveOneRuntime(runtimeId, opts));
    } catch (error) {
      if (error instanceof TypeError) continue; // C8: sweep skips, never dies
      throw error;
    }
  }
  return results;
}