import { execFileSync } from 'node:child_process';
import { existsSync } from 'node:fs';
import { join } from 'node:path';
import type { Plugin } from 'vite';

/**
 * ersatztv#819: hands `web/src/api/pageSizeCallSites.guard.test.ts` — the one SPA guard that derives a
 * file population — the set of files under `src/` that git actually tracks.
 *
 * That guard asserts EXACT completeness over the files it discovers, so its population has to be
 * the git index — `testing.guard-derives-population-from-source`. A directory walk is not an
 * authoritative source: an untracked `.ts`/`.tsx` under `web/src/` (a scratch file, a half-finished
 * component, an editor dropping) enters the population and fails as unregistered on that checkout
 * while CI, which only ever sees tracked files, stays green. That is the developer-red / CI-green
 * shape #778 named and #806 removed from every other guard here.
 *
 * Why a Vite plugin rather than `node:child_process` in the guard itself: `@types/node` is
 * deliberately absent from `tsconfig.app.json`, which covers production browser code too, and
 * wiring it in was tried and reverted — under `tsc -b`'s single-program compilation it leaked
 * Node's ambient `setTimeout` into the whole app project and broke three unrelated
 * `window.setTimeout` mocks expecting the DOM signature. A plugin runs in Vite's own Node context,
 * where `@types/node` is already available via `tsconfig.node.json`, and hands the result to the
 * app project as plain data. No app-project type change, no `/// <reference types="node" />`.
 *
 * SCOPE: the pathspec is `src/` only. A future guard over `web/e2e`, `web/scripts` or
 * `web/vite-plugins` must not import this module expecting its own files — it would receive a
 * silently truncated population, which is the defect this exists to remove. Widen the pathspec
 * (and say so here) rather than reusing it out of scope.
 */
export const TRACKED_SOURCE_FILES_ID = 'virtual:etv-tracked-source-files';

/** Rollup convention: a resolved virtual id is `\0`-prefixed so no other plugin claims it. */
const RESOLVED_ID = `\0${TRACKED_SOURCE_FILES_ID}`;

export interface TrackedSources {
  /** Tracked paths under `src/`, relative to the Vite root (`web/`), e.g. `src/api/pageSizeScan.ts`. */
  tracked: string[];
  /**
   * The subset of `tracked` with NO READABLE FILE at that path. Usually a working-tree deletion
   * that is not yet staged, which is the case the consumer tolerates — but the test is
   * `existsSync`, so it also covers a tracked BROKEN SYMLINK (a committed, permanent state, not a
   * mid-edit one), a sparse checkout that excludes the path, and an unreadable parent directory.
   * Named for what it measures rather than for the common cause, because a consumer subtracts this
   * set and a wrong name there licenses subtracting more than intended.
   *
   * Reported rather than silently removed: the consumer needs to tell these apart from a tracked
   * file the WALK cannot see, which is a real hole. Collapsing the two is how a population shrinks
   * without anyone noticing.
   */
  absentFromDisk: string[];
  /**
   * Paths under `src/` that git reports as UNTRACKED (ignored ones included), from a SEPARATE
   * `ls-files --others` query.
   *
   * This exists so the consumer can catch a narrowing of `tracked` itself (#819). Every
   * comparison the guard makes is between two things derived from `tracked`, so a filter applied
   * HERE shrinks both sides and cancels — real files leave the population with the whole suite
   * green, and the guard goes blind rather than merely quiet. `tracked ∪ others` is what is on
   * disk under `src/`, so a path the walk sees that is in NEITHER is the signal, and it is a signal
   * this list cannot suppress: narrowing `tracked` does not add anything to `others`.
   */
  others: string[];
}

/** Injectable so `resolveTrackedSourceFiles` is testable without a real repository. */
export type GitRunner = (args: readonly string[]) => string;
/** Injectable for the same reason; defaults to a real on-disk existence check. */
export type FileExists = (path: string) => boolean;

const runGitDefault: GitRunner = (args) =>
  execFileSync('git', [...args], {
    encoding: 'utf8',
    maxBuffer: 64 * 1024 * 1024,
    // Keep git's own `fatal: not a git repository` off the terminal so the framed error below is
    // the only message a reader sees.
    stdio: ['ignore', 'pipe', 'pipe']
  });

export function resolveTrackedSourceFiles(
  root: string,
  runGit: GitRunner = runGitDefault,
  fileExists: FileExists = existsSync
): TrackedSources {
  let raw: string;
  try {
    raw = runGit(['-C', root, 'ls-files', '-z', '--', 'src']);
  } catch (cause) {
    // FAIL, never degrade to the unfiltered walk. "Could not tell" is a third outcome distinct from
    // pass and fail, and a check that answers it by falling back to the population it exists to
    // replace is a permanent no-op that reports green — the shape ersatztv#772 was filed for.
    throw new Error(
      `${TRACKED_SOURCE_FILES_ID}: could not read the git index under ${root}. The SPA guard derives ` +
        `its population from it and must not fall back to a filesystem walk — fix the checkout ` +
        `rather than the guard.`,
      { cause }
    );
  }

  // `-z` rather than plain `ls-files`: git applies `core.quotePath` to non-ASCII names by default
  // and would hand back a C-quoted string that no longer matches the path Vite reports, silently
  // dropping that file from the population. NUL-separated output is never quoted.
  // Deduplicated: during a merge conflict `git ls-files` emits an unmerged path once per STAGE —
  // two for a both-added conflict, three for a content conflict. Nothing downstream needs the
  // repetition. It is tidiness rather than a fix: the ratio the floor computes uses the same list
  // on both sides, so duplicates cancel out of it (measured green with and without this).
  const tracked = [...new Set(raw.split('\0').filter((path) => path.length > 0))];
  if (tracked.length === 0) {
    // Anti-vacuity at the source. An empty population makes every completeness claim downstream
    // pass while proving nothing, which is the characteristic failure of a completeness check.
    throw new Error(
      `${TRACKED_SOURCE_FILES_ID}: git reported ZERO tracked files under ${root}/src. That is never ` +
        `true of this repository, so it means the index was not readable rather than that the ` +
        `population is genuinely empty.`
    );
  }

  let rawOthers: string;
  try {
    // Deliberately WITHOUT `--exclude-standard`: an ignored file is still a file on disk, and the
    // consumer's question is "is this path accounted for", not "should git have tracked it".
    rawOthers = runGit(['-C', root, 'ls-files', '-z', '--others', '--', 'src']);
  } catch (cause) {
    throw new Error(
      `${TRACKED_SOURCE_FILES_ID}: could not enumerate untracked files under ${root}. This list is ` +
        `what lets the consumer tell a narrowed index from a genuinely absent file, so it fails ` +
        `rather than degrading to an empty set.`,
      { cause }
    );
  }

  return {
    tracked,
    absentFromDisk: tracked.filter((path) => !fileExists(join(root, path))),
    others: rawOthers.split('\0').filter((path) => path.length > 0)
  };
}

export function trackedSourceFilesPlugin(runGit?: GitRunner, fileExists?: FileExists): Plugin {
  // Deliberately NOT seeded with `process.cwd()`. A wrong root is a silent wrong answer — git would
  // report zero files and the anti-vacuity throw would fire, but only by luck of this repo's
  // layout. Refusing is the honest outcome.
  let root: string | undefined;

  return {
    name: 'etv:tracked-source-files',
    configResolved(config) {
      root = config.root;
    },
    resolveId(id) {
      return id === TRACKED_SOURCE_FILES_ID ? RESOLVED_ID : undefined;
    },
    // Deliberately LAZY: git runs only when something imports the virtual module. `vite build`
    // never resolves this id and so never shells out to git. LOAD-BEARING FOR THE IMAGE BUILD since
    // ersatztv#887: `docker/Dockerfile`'s web-build stage runs `npm run build` in a stage with no git
    // binary, so making this eager would break every image build for #887's original root cause.
    load(id) {
      if (id !== RESOLVED_ID) {
        return undefined;
      }
      if (root === undefined) {
        throw new Error(
          `${TRACKED_SOURCE_FILES_ID}: the plugin's \`configResolved\` hook never ran, so the Vite ` +
            `root is unknown. Refusing to guess a root rather than derive a population from the wrong one.`
        );
      }
      return `export default ${JSON.stringify(resolveTrackedSourceFiles(root, runGit, fileExists))};\n`;
    }
  };
}