import fs from 'fs';
import path from 'path';
import { defineTool, ToolError } from 'libllmorbiter';
import { getStore } from '../db/store.js';
import { isReadOnlyDatabasePath, prepareVfs } from './vfs.js';
import { isSkillPath } from './skill.js';

/**
 * rm — deletes a single file from the virtual filesystem (VFS).
 *
 * This is the tool that makes a SKILL file removable. `reset_vfs` deliberately spares skills
 * so a routine cleanup cannot destroy authored knowledge; `rm` is the explicit, single-file
 * escape hatch for when a skill really should go (it is outdated, wrong, or superseded).
 *
 * Ported from fidoca's `rm`, with three differences forced by this environment:
 *
 *  - **No undo stack.** fidoca has `pushUndo`; dashback has no undo facility, so a delete here
 *    is immediate and final. The tool says so plainly so the model does not describe it as
 *    reversible.
 *  - **Deletes in both places.** fidoca only unlinks from disk. Here the VFS has two halves,
 *    so the database row must go too — otherwise the file reappears on the next
 *    `prepareVfs` hydration, which would make a "successful" delete silently undone.
 *  - **Guards the read-only image space**, matching `patch`, so a delete cannot be used to
 *    remove database images by writing to their path.
 *
 * Directories are refused: deleting a tree recursively is a bulk operation, and
 * `reset_vfs` already covers that case (while still sparing skills).
 */

/**
 * Validates a VFS-relative path and returns what is on disk at it.
 *
 * Performs no deletion itself — the caller sequences the database and disk writes, because
 * the order matters and only the tool wrapper knows about both halves.
 *
 * @param {string} vfsRoot
 * @param {string} relPath VFS-relative path, forward slashes
 * @returns {{ abs: string, size: number }} absolute path and size of the file
 * @throws {Error} on traversal, a missing path, or a directory
 */
export function deleteVfsFile(vfsRoot, relPath) {
    const abs = path.resolve(vfsRoot, relPath);
    const rel = path.relative(vfsRoot, abs);

    // Defence in depth: callers already check, but this helper is exported, so re-check here
    // rather than trusting the caller with a path-traversal primitive.
    if (rel.startsWith('..') || path.isAbsolute(rel)) {
        throw new Error(`Access denied: path "${relPath}" escapes virtual filesystem boundary.`);
    }

    if (!fs.existsSync(abs)) {
        throw new Error(`File not found: "${relPath}"`);
    }
    if (!fs.statSync(abs).isFile()) {
        throw new Error(`"${relPath}" is not a file. Use reset_vfs to clear directories (it keeps SKILL files).`);
    }

    return { abs, size: fs.statSync(abs).size };
}

/**
 * Creates the rm tool bound to a company's virtual filesystem.
 * @param {{ googleAuthId: number }} ctx
 */
export function createRmTool({ googleAuthId }) {
    return defineTool({
        name: 'rm',
        description:
            'Delete a single file from the virtual filesystem (VFS). ' +
            'Use this to remove a SKILL file: reset_vfs intentionally preserves skills, so rm is how a skill is ' +
            'deleted on purpose. Also use it to drop one unwanted artifact. ' +
            'Deletion is immediate and cannot be undone. Use reset_vfs to clear many files or a directory at once.',
        strict: false,
        parameters: {
            type: 'object',
            additionalProperties: false,
            required: ['filename'],
            properties: {
                filename: {
                    type: 'string',
                    description:
                        'File to delete, relative to the VFS root using forward slashes ' +
                        '(e.g. "image-pipeline.SKILL", "notes.md", "labels/sheet1.png").',
                },
            },
        },
        invoke: async ({ filename } = {}) => {
            if (typeof filename !== 'string' || !filename.trim()) {
                throw new ToolError('rm requires a non-empty "filename".');
            }

            const clean = filename.trim().replace(/^([a-zA-Z]:|\/)+/, '').replace(/^\.\/+/, '');
            if (!clean) {
                throw new ToolError('rm requires a non-empty "filename".');
            }

            if (isReadOnlyDatabasePath(clean)) {
                throw new ToolError(
                    `Access denied: "${clean}" matches the read-only database image pattern and cannot be deleted.`
                );
            }

            const vfsRoot = await prepareVfs({ googleAuthId });
            const { abs, size } = deleteVfsFile(vfsRoot, clean);

            // Database first. If this throws, the file is still on disk — recoverable, and the row
            // still exists to describe it. Doing it the other way round would leave a blob on
            // disk that the next prepareVfs hydration would restore, silently undoing the delete.
            const store = await getStore();
            const res = await store.modelvfs.delete(googleAuthId, clean);

            fs.unlinkSync(abs);

            const wasSkill = isSkillPath(clean);
            const result = {
                success: true,
                deleted: res?.deleted !== false,
                filename: clean,
                size,
                message: `Deleted "${clean}" (${size} bytes). This cannot be undone.`,
            };
            if (wasSkill) {
                result.type = 'skill';
                result.note = 'SKILL file deleted. It will not be restored by reset_vfs.';
            }
            return result;
        },
    });
}