// Large-course mode — Layer 1: course framework generation agent.
//
// Takes a single requirement (optionally with PDF text and web-search research
// context) and produces a CourseFramework: course title, teaching-language
// directive, summary, and 4–15 modules. Each module must be a self-contained
// teaching unit that the Layer-2 single-courseware agent will turn into a full
// courseware. Prompt lives in lib/prompts/templates/course-framework/.

import { buildPrompt, PROMPT_IDS } from '@/lib/prompts';
import { parseJsonResponse } from '@openmaic/generation';
import { createLogger } from '@/lib/logger';
import type { CourseFramework } from './types';

const log = createLogger('CourseFramework');

export interface CourseFrameworkInput {
  requirement: string;
  pdfText?: string;
  researchContext?: string;
}

export interface CourseFrameworkGenerationResult {
  success: boolean;
  data?: CourseFramework;
  error?: string;
}

export type FrameworkAICallFn = (systemPrompt: string, userPrompt: string) => Promise<string>;

export const MIN_COURSE_MODULES = 4;
export const MAX_COURSE_MODULES = 15;

function readRequiredString(value: unknown): string {
  return typeof value === 'string' ? value.trim() : '';
}

function readStringArray(value: unknown): string[] | null {
  if (!Array.isArray(value)) return null;
  const items = value.map((item) => readRequiredString(item));
  return items.some((item) => !item) ? null : items;
}

function buildUserPrompt(input: CourseFrameworkInput): string {
  const pdfSection = input.pdfText
    ? `\n\n## 参考文档（PDF 提取文本）\n\n${input.pdfText.slice(0, 6000)}`
    : '';
  const researchSection = input.researchContext
    ? `\n\n## 联网研究资料（供参考）\n\n${input.researchContext.slice(0, 8000)}`
    : '';
  return (
    buildPrompt(PROMPT_IDS.COURSE_FRAMEWORK, {
      requirement: input.requirement,
      pdfSection,
      researchSection,
    })?.user ?? ''
  );
}

/** Validate a raw parsed framework; returns a normalized framework or a reason. */
export function validateCourseFramework(raw: unknown): CourseFramework | null {
  if (!raw || typeof raw !== 'object' || Array.isArray(raw)) return null;
  const obj = raw as Record<string, unknown>;

  const courseTitle = readRequiredString(obj.courseTitle);
  const languageDirective = readRequiredString(obj.languageDirective);
  const targetAudience = readRequiredString(obj.targetAudience);
  const summary = readRequiredString(obj.summary);
  const courseGoals = readStringArray(obj.courseGoals);
  const continuity =
    obj.continuityContract &&
    typeof obj.continuityContract === 'object' &&
    !Array.isArray(obj.continuityContract)
      ? (obj.continuityContract as Record<string, unknown>)
      : null;
  const terminology = readStringArray(continuity?.terminology);
  const teachingStyle = readRequiredString(continuity?.teachingStyle);
  const difficultyProgression = readRequiredString(continuity?.difficultyProgression);
  const assessmentStrategy = readRequiredString(continuity?.assessmentStrategy);
  if (
    !courseTitle ||
    !languageDirective ||
    !targetAudience ||
    !summary ||
    !courseGoals?.length ||
    !terminology?.length ||
    !teachingStyle ||
    !difficultyProgression ||
    !assessmentStrategy
  ) {
    return null;
  }
  if (courseTitle.length > 60) return null;

  if (!Array.isArray(obj.modules) || obj.modules.length === 0) return null;
  if (obj.modules.length < MIN_COURSE_MODULES || obj.modules.length > MAX_COURSE_MODULES) {
    return null;
  }

  const modules = obj.modules.map((m, i) => {
    if (!m || typeof m !== 'object' || Array.isArray(m)) return null;
    const mod = m as Record<string, unknown>;
    const title = readRequiredString(mod.title);
    const description = readRequiredString(mod.description);
    const objectives = readStringArray(mod.learningObjectives);
    const generationPrompt = readRequiredString(mod.generationPrompt);
    const incomingKnowledge = readStringArray(mod.incomingKnowledge);
    const outgoingKnowledge = readStringArray(mod.outgoingKnowledge);
    const excludedTopics = readStringArray(mod.excludedTopics);
    if (
      !title ||
      title.length > 60 ||
      !description ||
      !objectives?.length ||
      !generationPrompt ||
      !incomingKnowledge ||
      !outgoingKnowledge?.length ||
      !excludedTopics
    ) {
      return null;
    }
    const prerequisites =
      typeof mod.prerequisites === 'string' && mod.prerequisites.trim()
        ? mod.prerequisites.trim()
        : undefined;
    if (typeof mod.estimatedMinutes !== 'number' || !Number.isFinite(mod.estimatedMinutes)) {
      return null;
    }
    const estimatedMinutes = Math.min(Math.max(Math.round(mod.estimatedMinutes), 5), 60);
    return {
      index: i + 1,
      title,
      description,
      learningObjectives: objectives,
      generationPrompt,
      ...(prerequisites ? { prerequisites } : {}),
      incomingKnowledge,
      outgoingKnowledge,
      excludedTopics,
      estimatedMinutes,
    };
  });

  if (modules.some((m) => m === null)) return null;

  return {
    courseTitle,
    languageDirective,
    targetAudience,
    summary,
    courseGoals,
    continuityContract: {
      terminology,
      teachingStyle,
      difficultyProgression,
      assessmentStrategy,
    },
    modules: modules as NonNullable<(typeof modules)[number]>[],
  };
}

/**
 * Run the Layer-1 framework generation with one retry on parse/validation
 * failure. The retry re-sends the model's own raw output as a correction hint
 * so the second call can fix its JSON.
 */
export async function generateCourseFramework(
  input: CourseFrameworkInput,
  aiCall: FrameworkAICallFn,
  options: { maxAttempts?: number } = {},
): Promise<CourseFrameworkGenerationResult> {
  const maxAttempts = options.maxAttempts ?? 2;
  const system =
    buildPrompt(PROMPT_IDS.COURSE_FRAMEWORK, {
      requirement: input.requirement,
      pdfSection: '',
      researchSection: '',
    })?.system ?? '';
  const userBase = buildUserPrompt(input);

  let lastError = 'unknown error';
  for (let attempt = 1; attempt <= maxAttempts; attempt += 1) {
    const user =
      attempt === 1
        ? userBase
        : `${userBase}\n\n上一次输出无法解析：${lastError}\n请只输出符合要求的 JSON。`;
    const response = await aiCall(system, user);
    if (!response.trim()) {
      lastError = 'empty model response';
      continue;
    }
    const parsed = parseJsonResponse<unknown>(response);
    if (!parsed) {
      lastError = 'output is not valid JSON';
      log.warn(`Course framework attempt ${attempt}/${maxAttempts}: invalid JSON`);
      continue;
    }
    const framework = validateCourseFramework(parsed);
    if (!framework) {
      lastError =
        'JSON failed validation (module count outside 4–15, or missing course goals, continuity contract, module generation prompt, knowledge boundaries, or duration)';
      log.warn(`Course framework attempt ${attempt}/${maxAttempts}: validation failed`);
      continue;
    }
    log.info(
      `Course framework generated: "${framework.courseTitle}" with ${framework.modules.length} modules`,
    );
    return { success: true, data: framework };
  }
  return { success: false, error: lastError };
}