import path from 'node:path';
import type { TeacherRequest, TeacherSourceContext } from '../../shared/coding-teacher';
import { CodingProjectFileService } from '../coding-projects/project-files';
import { excerptTeacherText, teacherHistoryMessages } from './context';
import { readInteger, readPage, textChunks } from './read-page';

export const TEACHER_READ_PROTOCOL = 2;
export const TEACHER_READ_ROUNDS = 12;
export const TEACHER_READ_BYTES = 64 * 1024;
export const TEACHER_READ_PAGE_BYTES = 8 * 1024;
export const TEACHER_READ_MIN_BYTES = 512;

export interface TeacherReadAccess {
  projectPath: string;
  source: TeacherSourceContext;
  history?: TeacherRequest[];
  assertCurrent(): void;
}

const lineParameters = {
  start_line: { type: 'integer', minimum: 1, description: 'First line, default 1.' },
  start_column: { type: 'integer', minimum: 1, description: 'Unicode character column, default 1. Copy next from the previous page to continue.' },
  line_count: { type: 'integer', minimum: 1, maximum: 400, description: 'Maximum lines, default 120. Output is bounded; use next for the exact continuation.' },
};
export const teacherReadToolDefinitions = [
  { type: 'function', function: {
    name: 'list_project_files', description: 'List a bounded project tree. Start with path "."; use relevant subdirectories for deeper exploration. Files unchanged during a page sequence have stable line order.',
    parameters: { type: 'object', properties: { path: { type: 'string' }, depth: { type: 'integer', minimum: 1, maximum: 6, description: 'Tree depth, default 4. Directories at the depth boundary can be listed separately.' }, ...lineParameters }, required: ['path'], additionalProperties: false },
  } },
  { type: 'function', function: {
    name: 'read_project_file', description: 'Read UTF-8 source from a current-project relative path, including .makelore/project.json metadata. Read only; no commands or edits.',
    parameters: { type: 'object', properties: { path: { type: 'string' }, ...lineParameters }, required: ['path'], additionalProperties: false },
  } },
  { type: 'function', function: {
    name: 'read_conversation', description: 'Read the captured active coding conversation and current teacher topic. Omit message_id to list messages; supply it to read continuous original text. Results give start_line/start_column and next; do not reread unchanged ranges.',
    parameters: { type: 'object', properties: { message_id: { type: 'string' }, ...lineParameters }, additionalProperties: false },
  } },
];

function projectPath(value: unknown): string {
  if (typeof value !== 'string' || !value.trim()) throw new Error('A relative project path is required.');
  const normalized = path.posix.normalize(value.trim().replaceAll('\\', '/'));
  if (normalized.toLowerCase() !== '.makelore/project.json'
    && normalized.split('/').some(part => ['.makelore', '.git'].includes(part.toLowerCase()))) {
    throw new Error('Application history and Git internals are not project source files.');
  }
  return normalized;
}

export function createTeacherReadTools(access: TeacherReadAccess) {
  const files = new CodingProjectFileService();
  const messages = [...access.source.messages, ...teacherHistoryMessages(access.history ?? [])];
  return {
    definitions: teacherReadToolDefinitions,
    async execute(name: string, rawArguments: string, signal: AbortSignal, maxBytes = TEACHER_READ_PAGE_BYTES): Promise<string> {
      return (await this.executeResult(name, rawArguments, signal, maxBytes)).content;
    },
    async executeResult(name: string, rawArguments: string, signal: AbortSignal, maxBytes = TEACHER_READ_PAGE_BYTES): Promise<{ status: 'success' | 'error'; content: string; truncated: boolean }> {
      signal.throwIfAborted();
      access.assertCurrent();
      let result: string;
      let status: 'success' | 'error' = 'success';
      let truncated = false;
      try {
        const args = JSON.parse(rawArguments) as Record<string, unknown>;
        if (!args || typeof args !== 'object' || Array.isArray(args)) throw new Error('Expected an object.');
        switch (name) {
          case 'list_project_files': {
            const root = projectPath(args.path);
            const depth = readInteger(args.depth, 4, 6);
            async function* tree(): AsyncGenerator<string> {
              const directories = [{ path: root, level: 1 }];
              let found = false;
              for (let i = 0; i < directories.length; i++) {
                signal.throwIfAborted();
                access.assertCurrent();
                const directory = directories[i];
                for (const entry of await files.directory(access.projectPath, directory.path)) {
                  if (['.makelore', '.git', '.gradle'].includes(entry.name.toLowerCase())) continue;
                  found = true;
                  yield entry.path + (entry.type === 'directory' ? '/' : '') + '\n';
                  if (entry.type === 'directory' && directory.level < depth)
                    directories.push({ path: entry.path, level: directory.level + 1 });
                }
              }
              if (!found) yield '(empty directory)';
            }
            ({ content: result, truncated } = await readPage(root + ' (tree depth ' + depth + ')',
              tree(), args, maxBytes));
            break;
          }
          case 'read_project_file': {
            const target = projectPath(args.path);
            ({ content: result, truncated } = await readPage(target,
              files.textChunks(access.projectPath, target, signal), args, maxBytes));
            break;
          }
          case 'read_conversation': {
            const message = args.message_id === undefined ? undefined : messages.find(item => item.id === args.message_id);
            if (args.message_id !== undefined && !message) throw new Error('Message is not in the current conversation.');
            const text = message?.text ?? (messages.map(item =>
              `${item.id} ${item.role}: ${excerptTeacherText(item.text, 180).replaceAll('\n', ' ')}`).join('\n')
              || '(no completed text messages in this conversation)');
            ({ content: result, truncated } = await readPage(message ? message.id + ' ' + message.role : 'conversation message index (snippets)',
              textChunks(text), args, maxBytes));
            break;
          }
          default:
            throw new Error('Only list_project_files, read_project_file and read_conversation are available.');
        }
      } catch (error) {
        status = 'error';
        // Keep local OS paths and unrelated application data out of model errors.
        result = 'Read failed. Check the relative path, message id and line range. '
          + (error instanceof SyntaxError ? 'Tool arguments must be valid JSON.' : 'Only current-project text files and current-conversation messages are available.');
      }
      signal.throwIfAborted();
      access.assertCurrent();
      // Only the generic error can need truncation; source pages already fit exactly.
      const content = status === 'error' ? excerptTeacherText(result, maxBytes) : result;
      return { status, content, truncated: truncated || content !== result };
    },
  };
}

export type TeacherReadTools = ReturnType<typeof createTeacherReadTools>;