'use strict';

/**
 * File-browser helpers for prompt file mentions.
 *
 * Pure, terminal-free helpers used by the in-prompt file browser in
 * `autocomplete-input.js`. Keeping them here means the listing, mention
 * formatting and range math can be unit-tested without a TTY.
 *
 * Everything path-related stays relative to `ROOT_DIR` and uses forward
 * slashes, matching the rest of the system (`list_files`, `read_file`,
 * `ripgrep`). File reads are constrained to the workspace via `resolveSafe`.
 */

import fs from 'fs';
import path from 'path';

import { ROOT_DIR } from './config.js';
import { listDir } from './dir-listing.js';
import { resolveSafe } from './sandbox.js';

/** Normalize a workspace-relative path to forward slashes, no trailing slash. */
function normalizeRel(rel) {
    return String(rel || '').replace(/\\/g, '/').replace(/\/+$/, '');
}

/** Return the parent of a workspace-relative directory path ('' at the root). */
export function parentOf(cwd) {
    const rel = normalizeRel(cwd);
    if (!rel) return '';
    const idx = rel.lastIndexOf('/');
    return idx === -1 ? '' : rel.slice(0, idx);
}

/** Basename of a workspace-relative path. */
export function baseOf(rel) {
    const clean = normalizeRel(rel);
    const idx = clean.lastIndexOf('/');
    return idx === -1 ? clean : clean.slice(idx + 1);
}

/**
 * List the entries of a workspace-relative directory for the browser.
 *
 * Directories come first (then files), each alphabetically. A synthetic
 * `..` entry is prepended unless we are already at the workspace root.
 * Respects `.gitignore` and hides dot-directories by delegating to `listDir`.
 *
 * Returns an array of `{ name, rel, type }` where `type` is one of
 * `'parent' | 'd' | 'f'` and `rel` is relative to `ROOT_DIR` (no trailing
 * slash; '' for the parent entry at depth 1).
 */
export function listEntries(cwd = '') {
    const rel = normalizeRel(cwd);
    const dir = rel ? path.join(ROOT_DIR, rel) : ROOT_DIR;
    const { entries } = listDir(dir, { seek: 0, limit: Number.MAX_SAFE_INTEGER });

    const dirs = entries.filter((e) => e.type === 'd');
    const files = entries.filter((e) => e.type === 'f');
    const byName = (a, b) => a.path.localeCompare(b.path);
    dirs.sort(byName);
    files.sort(byName);

    const out = [];
    if (rel) out.push({ name: '..', rel: parentOf(rel), type: 'parent' });
    for (const e of dirs) {
        const childRel = normalizeRel(e.path);
        out.push({ name: baseOf(childRel), rel: childRel, type: 'd' });
    }
    for (const e of files) {
        const childRel = normalizeRel(e.path);
        out.push({ name: baseOf(childRel), rel: childRel, type: 'f' });
    }
    return out;
}

/**
 * Read a workspace-relative file as an array of lines (split on `\n`).
 *
 * Returns `{ lines, binary }`. An empty file yields `[]`. A file containing a
 * NUL byte in its first 8000 bytes is reported as binary with no lines, so the
 * line selector can fall back to a whole-file mention without garbling output.
 * Read/permission errors yield `{ lines: [], binary: false, error: true }`
 * rather than throwing, so the browser can refresh and keep going.
 */
export function readLines(relPath) {
    let abs;
    try {
        abs = resolveSafe(relPath);
    } catch {
        return { lines: [], binary: false, error: true };
    }
    let buf;
    try {
        buf = fs.readFileSync(abs);
    } catch {
        return { lines: [], binary: false, error: true };
    }
    if (buf.subarray(0, 8000).includes(0)) {
        return { lines: [], binary: true };
    }
    const text = buf.toString('utf8');
    const lines = text.length === 0 ? [] : text.split('\n');
    return { lines, binary: false };
}

/**
 * Format a mention for insertion into the prompt.
 *
 *   formatMention('a/b.js')          -> '@a/b.js'
 *   formatMention('a/b.js', 10, 10)  -> '@a/b.js:10'
 *   formatMention('a/b.js', 10, 20)  -> '@a/b.js:10-20'
 */
export function formatMention(relPath, start, end) {
    const p = normalizeRel(relPath);
    if (start === undefined || start === null) return `@${p}`;
    if (end === undefined || end === null || end === start) return `@${p}:${start}`;
    return `@${p}:${start}-${end}`;
}

/**
 * Normalize a marked range from two 0-based line indices to the 1-based
 * `{ start, end }` shown to the user (start <= end).
 */
export function normalizeRange(anchor, cursor) {
    const a = Math.min(anchor, cursor);
    const b = Math.max(anchor, cursor);
    return { start: a + 1, end: b + 1 };
}

/**
 * Top index of the visible window of `size` rows that keeps `cursor` in view.
 * Returns 0 when everything fits.
 */
export function windowStart(cursor, total, size) {
    if (total <= size) return 0;
    let start = cursor - Math.floor(size / 2);
    if (start < 0) start = 0;
    if (start + size > total) start = total - size;
    return start;
}