import { OpenAICompatibleClient } from "./client";
import { GenerationError } from "./errors";
import { parseAiJsonResponse } from "./parse-response";
import {
  getPassageJsonSchemaDescription,
  getValidationJsonSchemaDescription,
  getSelfValidationJsonSchemaDescription,
} from "./schema-to-prompt";
import {
  getGenericQuestionJsonSchemaDescription,
  repairAndParseQuestions,
} from "./repair";
import { regenerateQuestions, buildRegenerationContext } from "./regenerate-questions";
import { OPTION_QUALITY_RULES } from "./prompts";
import {
  getTargetLanguage,
  buildContentLanguageRules,
  buildExplanationLanguageRule,
} from "./language-rules";
import { type GenerationInput, type GenerationResult } from "./schemas";

interface AgenticStep {
  step: string;
  status: "running" | "done" | "error" | "pending";
  message?: string;
  output?: string;
}

export interface AgenticProgress {
  steps: AgenticStep[];
  currentStep: number;
}

export type AgenticGenerationStrategy = "full" | "lean";

export interface AgenticGenerationOptions {
  strategy?: AgenticGenerationStrategy;
  maxRegenerateAttempts?: number;
}

function getSystemPrompt(): string {
  return "You are a precise exam question generator. You always return valid JSON. You never include markdown formatting around the JSON.";
}

export { getTargetLanguage };

/** Estimate max tokens needed per step to avoid truncation. */
function calculateMaxTokens(
  userMax: number,
  step: "passage" | "validate" | "questions" | "self_validate" | "regenerate",
  questionCount: number,
): number {
  const base = userMax > 0 ? userMax : 16_384;
  switch (step) {
    case "passage":
      return Math.min(Math.max(base, 6_000), 16_384);
    case "validate":
      return Math.min(base, 4_096);
    case "self_validate":
      return Math.min(base, 4_096);
    case "questions":
      // Rough estimate: ~500 tokens per question JSON + overhead
      return Math.min(Math.max(base, 2_000 + questionCount * 600), 64_000);
    case "regenerate":
      return Math.min(Math.max(base, 2_000 + questionCount * 600), 64_000);
    default:
      return base;
  }
}

function parseJsonResponse(content: string): unknown {
  return parseAiJsonResponse(content);
}

async function step1GeneratePassage(
  client: OpenAICompatibleClient,
  input: GenerationInput,
  onToken?: (token: string) => void,
): Promise<{ passage: string; title: string; tokensUsed: number }> {
  const schema = getPassageJsonSchemaDescription();
  const prompt = `Generate an authentic, high-quality reading passage for ${input.examType} ${input.section.toLowerCase()} section at difficulty level ${input.difficulty}/5.

Requirements:
- Language: ${getTargetLanguage(input.examType)}
- Topics: ${input.topics.join(", ")}
- Difficulty: ${input.difficulty}/5
- The passage should be natural, well-structured, and appropriate for the exam level
- Length should be suitable for ${input.questionCount} comprehension questions

Return ONLY valid JSON conforming to this schema:
${schema}`;

  const result = await client.chatCompletion(
    {
      model: input.apiKeyConfig.model,
      messages: [
        { role: "system", content: getSystemPrompt() },
        { role: "user", content: prompt },
      ],
      temperature: 0.7,
      max_tokens: calculateMaxTokens(input.apiKeyConfig.maxTokens, "passage", input.questionCount),
      response_format: { type: "json_object" },
    },
    onToken ? { onToken } : undefined,
  );

  const parsed = parseJsonResponse(result.content) as Record<string, unknown>;
  if (!parsed.passage || typeof parsed.passage !== "string") {
    throw new Error("Invalid passage generation response");
  }
  return {
    passage: parsed.passage,
    title: typeof parsed.title === "string" ? parsed.title : "Untitled Passage",
    tokensUsed: result.usage?.total_tokens ?? 0,
  };
}

async function step2ValidatePassage(
  client: OpenAICompatibleClient,
  input: GenerationInput,
  passage: string,
  onToken?: (token: string) => void,
): Promise<{ isValid: boolean; feedback: string; tokensUsed: number }> {
  const schema = getValidationJsonSchemaDescription();
  const prompt = `Validate this reading passage for a ${input.examType} exam at difficulty ${input.difficulty}/5.

Passage:
"""
${passage}
"""

Check:
1. Grammar and spelling correctness
2. Difficulty appropriateness (${input.difficulty}/5)
3. Length sufficiency for ${input.questionCount} questions
4. Topic relevance: ${input.topics.join(", ")}
5. Natural flow and coherence

Return ONLY valid JSON conforming to this schema:
${schema}`;

  const result = await client.chatCompletion(
    {
      model: input.apiKeyConfig.model,
      messages: [
        { role: "system", content: getSystemPrompt() },
        { role: "user", content: prompt },
      ],
      temperature: 0.3,
      max_tokens: calculateMaxTokens(input.apiKeyConfig.maxTokens, "validate", input.questionCount),
      response_format: { type: "json_object" },
    },
    onToken ? { onToken } : undefined,
  );

  const parsed = parseJsonResponse(result.content) as Record<string, unknown>;
  return {
    isValid: !!parsed.isValid,
    feedback: typeof parsed.feedback === "string" ? parsed.feedback : "No feedback",
    tokensUsed: result.usage?.total_tokens ?? 0,
  };
}

async function step3GenerateQuestions(
  client: OpenAICompatibleClient,
  input: GenerationInput,
  passage: string,
  count: number,
  onToken?: (token: string) => void,
): Promise<{ questions: Array<Record<string, unknown>>; tokensUsed: number }> {
  const schema = getGenericQuestionJsonSchemaDescription();

  const prompt = `Using the following passage, generate ${count} reading comprehension questions for ${input.examType} exam.

Passage:
"""
${passage}
"""

Formats to generate: ${input.formats.join(", ")}

Rules:
- Each question must be directly answerable from the passage
- Use "passageText" field with the relevant excerpt from the passage (or full passage if needed)
- Questions should test real comprehension, not surface recall
- For multiple choice: always provide 5 options (A, B, C, D, E) with one clearly correct answer
- Options must be plausible distractors
${OPTION_QUALITY_RULES}
${buildContentLanguageRules(input.examType)}
${buildExplanationLanguageRule(input.examType)}
- For true_false_not_given: correctAnswer must be exactly TRUE, FALSE, or NOT_GIVEN (uppercase)
- For author_view: correctAnswer must be exactly YES, NO, or NOT_GIVEN (uppercase)
- For matching_pairs: options are {key, text} pairs. correctAnswer is serialized mapping like "A:1,B:2".
- For error_recognition: options are error segments. correctAnswer is key of segment with error.
- For text_insertion: options are position markers. correctAnswer is best position key.

Question schema:
${schema}

Return ONLY valid JSON conforming to this schema.`;

  const result = await client.chatCompletion(
    {
      model: input.apiKeyConfig.model,
      messages: [
        { role: "system", content: getSystemPrompt() },
        { role: "user", content: prompt },
      ],
      temperature: 0.7,
      max_tokens: calculateMaxTokens(input.apiKeyConfig.maxTokens, "questions", count),
      response_format: { type: "json_object" },
    },
    onToken ? { onToken } : undefined,
  );

  const parsed = parseJsonResponse(result.content) as Record<string, unknown>;
  if (!Array.isArray(parsed.questions)) {
    throw new Error("Missing questions array in AI response");
  }
  return {
    questions: parsed.questions as Array<Record<string, unknown>>,
    tokensUsed: result.usage?.total_tokens ?? 0,
  };
}

function formatQuestionForValidation(q: Record<string, unknown>, index: number): string {
  const lines = [`Q${index + 1}: ${q.questionText}`];
  if (Array.isArray(q.options) && q.options.length > 0) {
    const optionLines = q.options
      .map((o) => {
        const opt = o as Record<string, unknown>;
        const key = opt.key ?? opt.left ?? "?";
        const text = opt.text ?? opt.right ?? "";
        return `  ${key}: ${text}`;
      })
      .join("\n");
    lines.push(`Options:\n${optionLines}`);
  }
  lines.push(`Claimed answer: ${q.correctAnswer}`);
  return lines.join("\n");
}

async function step4SelfValidate(
  client: OpenAICompatibleClient,
  input: GenerationInput,
  passage: string,
  questions: Array<Record<string, unknown>>,
  onToken?: (token: string) => void,
): Promise<{ confidence: number; issues: unknown[]; tokensUsed: number }> {
  const qaPairs = questions
    .map((q, i) => formatQuestionForValidation(q, i))
    .join("\n\n");

  const schema = getSelfValidationJsonSchemaDescription();
  const prompt = `You are a strict exam validator. Review these questions against the passage and identify any errors.

Passage:
"""
${passage}
"""

Questions & Claimed Answers:
${qaPairs}

For each question, verify:
1. Is the claimed answer truly correct based on the passage?
2. Are there any ambiguous questions?
3. Are distractors plausible but clearly wrong?
4. Are all option texts meaningful (not generic placeholders like "Option A")?

Return ONLY valid JSON conforming to this schema:
${schema}`;

  const result = await client.chatCompletion(
    {
      model: input.apiKeyConfig.model,
      messages: [
        { role: "system", content: getSystemPrompt() },
        { role: "user", content: prompt },
      ],
      temperature: 0.3,
      max_tokens: calculateMaxTokens(input.apiKeyConfig.maxTokens, "self_validate", input.questionCount),
      response_format: { type: "json_object" },
    },
    onToken ? { onToken } : undefined,
  );

  const parsed = parseJsonResponse(result.content) as Record<string, unknown>;
  const confidence = typeof parsed.overallConfidence === "number" ? parsed.overallConfidence : 75;
  const issues = Array.isArray(parsed.issues) ? parsed.issues : [];

  return { confidence, issues, tokensUsed: result.usage?.total_tokens ?? 0 };
}

export async function generatePassageForInput(
  input: GenerationInput,
  onToken?: (token: string) => void,
): Promise<{ passage: string; title: string; tokensUsed: number }> {
  const client = new OpenAICompatibleClient(
    input.apiKeyConfig.baseUrl,
    input.apiKeyConfig.apiKey,
  );
  return step1GeneratePassage(client, input, onToken);
}

/** Generate + validate questions from an existing passage (skips passage generation). */
export async function generateQuestionsAgenticFromPassage(
  input: GenerationInput,
  passage: string,
  onProgress?: (progress: AgenticProgress) => void,
  onToken?: (token: string) => void,
  options?: AgenticGenerationOptions,
): Promise<GenerationResult> {
  const start = Date.now();
  const strategy = options?.strategy ?? "full";
  const maxRegenAttempts = Math.max(0, options?.maxRegenerateAttempts ?? (strategy === "lean" ? 1 : 2));
  const client = new OpenAICompatibleClient(
    input.apiKeyConfig.baseUrl,
    input.apiKeyConfig.apiKey,
  );

  const steps: [AgenticStep, AgenticStep, AgenticStep, AgenticStep] = [
    { step: "generate_passage", status: "done", message: "Using shared passage" },
    { step: "validate_passage", status: "done", message: "Skipped (shared passage)" },
    { step: "generate_questions", status: "running" },
    { step: "self_validate", status: "pending" as any },
  ];

  const report = (current: number, extraMsg?: string) => {
    if (extraMsg && steps[current]) {
      steps[current]!.message = extraMsg;
    }
    if (onProgress) {
      onProgress({ steps, currentStep: current });
    }
  };

  let accumulatedTokens = 0;
  return runAgenticQuestionPipeline({
    client,
    input,
    passage,
    steps,
    report,
    strategy,
    maxRegenAttempts,
    onToken,
    start,
    accumulatedTokens,
  });
}

async function runAgenticQuestionPipeline(ctx: {
  client: OpenAICompatibleClient;
  input: GenerationInput;
  passage: string;
  steps: [AgenticStep, AgenticStep, AgenticStep, AgenticStep];
  report: (current: number, extraMsg?: string) => void;
  strategy: AgenticGenerationStrategy;
  maxRegenAttempts: number;
  onToken?: (token: string) => void;
  start: number;
  accumulatedTokens: number;
}): Promise<GenerationResult> {
  const {
    client,
    input,
    passage,
    steps,
    report,
    strategy,
    maxRegenAttempts,
    onToken,
    start,
  } = ctx;
  let accumulatedTokens = ctx.accumulatedTokens;

  steps[2]!.status = "running";
  report(2, `Generating ${input.questionCount} questions...`);
  let rawQuestions: Array<Record<string, unknown>>;
  try {
    const s3 = await step3GenerateQuestions(client, input, passage, input.questionCount, onToken);
    rawQuestions = s3.questions;
    accumulatedTokens += s3.tokensUsed;
    steps[2]!.status = "done";
    steps[2]!.message = `Generated ${rawQuestions.length} questions`;
    steps[2]!.output = rawQuestions.map((q, i) => `${i + 1}. [${q.format}] ${q.questionText}`).join("\n");
    report(2);
  } catch (err: any) {
    steps[2]!.status = "error";
    steps[2]!.message = err.message ?? "Question generation failed";
    throw new GenerationError(`Step 3 failed: ${err.message}`, { tokensUsed: accumulatedTokens });
  }

  steps[3]!.status = "running";
  report(3, "Validating & repairing questions...");

  let validQuestions: any[] = [];
  let allRepairLogs: string[] = [];

  try {
    let selfValidationConfidence = 0;
    if (strategy === "full") {
      const s4 = await step4SelfValidate(client, input, passage, rawQuestions, onToken);
      accumulatedTokens += s4.tokensUsed;
      selfValidationConfidence = s4.confidence;
    }

    let { valid, invalid, repairLog } = repairAndParseQuestions(rawQuestions, passage, {
      examType: input.examType,
      strictExplanation: strategy === "full",
    });

    validQuestions = valid;
    invalid = [...invalid];
    allRepairLogs.push(...repairLog);

    let regenerationAttempts = 0;

    while (invalid.length > 0 && regenerationAttempts < maxRegenAttempts && validQuestions.length < input.questionCount) {
      regenerationAttempts++;
      const regenCount = Math.min(invalid.length, input.questionCount - validQuestions.length);
      const context = buildRegenerationContext(invalid.slice(0, regenCount));

      report(3, `Regenerating ${regenCount} invalid question(s) (attempt ${regenerationAttempts}/${maxRegenAttempts})...`);

      const regen = await regenerateQuestions(client, input, passage, regenCount, context, onToken);
      accumulatedTokens += regen.tokensUsed;

      const regenResult = repairAndParseQuestions(regen.questions, passage, {
        examType: input.examType,
        strictExplanation: strategy === "full",
      });
      validQuestions.push(...regenResult.valid);
      allRepairLogs.push(...regenResult.repairLog.map((l) => `[Regen ${regenerationAttempts}] ${l}`));

      if (regenResult.valid.length > 0) {
        invalid = invalid.slice(regenResult.valid.length);
      } else {
        break;
      }
    }

    if (validQuestions.length < input.questionCount) {
      const needMore = input.questionCount - validQuestions.length;
      report(3, `Generating ${needMore} additional question(s)...`);
      const extra = await regenerateQuestions(
        client, input, passage, needMore,
        `Need ${needMore} more valid questions to reach target of ${input.questionCount}.`,
        onToken,
      );
      accumulatedTokens += extra.tokensUsed;
      const extraResult = repairAndParseQuestions(extra.questions, passage, {
        examType: input.examType,
        strictExplanation: strategy === "full",
      });
      validQuestions.push(...extraResult.valid);
      allRepairLogs.push(...extraResult.repairLog.map((l) => `[Extra] ${l}`));
    }

    steps[3]!.status = "done";
    steps[3]!.message =
      strategy === "full"
        ? `Validated ${validQuestions.length}/${input.questionCount} questions. Confidence: ${selfValidationConfidence}%`
        : `Lean validation completed: ${validQuestions.length}/${input.questionCount} valid`;
    steps[3]!.output = [
      `Strategy: ${strategy}`,
      ...(strategy === "full" ? [`Overall Confidence: ${selfValidationConfidence}%`] : []),
      `Valid Questions: ${validQuestions.length}/${input.questionCount}`,
      `Repair Log:`,
      ...allRepairLogs,
    ].join("\n");
    report(3);
  } catch (err: any) {
    steps[3]!.status = "error";
    steps[3]!.message = err.message ?? "Self-validation failed";
    throw new GenerationError(`Step 4 failed: ${err.message}`, { tokensUsed: accumulatedTokens });
  }

  if (validQuestions.length === 0) {
    throw new GenerationError("No valid questions generated after agentic validation", {
      tokensUsed: accumulatedTokens,
    });
  }

  const finalQuestions = validQuestions.slice(0, input.questionCount);

  return {
    questions: finalQuestions,
    meta: {
      model: input.apiKeyConfig.model,
      durationMs: Date.now() - start,
      mode: "agentic",
      tokensUsed: accumulatedTokens,
    },
  };
}

export async function generateQuestionsAgentic(
  input: GenerationInput,
  onProgress?: (progress: AgenticProgress) => void,
  onToken?: (token: string) => void,
  options?: AgenticGenerationOptions,
): Promise<GenerationResult> {
  const start = Date.now();
  const strategy = options?.strategy ?? "full";
  const maxRegenAttempts = Math.max(0, options?.maxRegenerateAttempts ?? (strategy === "lean" ? 1 : 2));
  const client = new OpenAICompatibleClient(
    input.apiKeyConfig.baseUrl,
    input.apiKeyConfig.apiKey,
  );

  const steps: [AgenticStep, AgenticStep, AgenticStep, AgenticStep] = [
    { step: "generate_passage", status: "running" },
    { step: "validate_passage", status: "pending" as any },
    { step: "generate_questions", status: "pending" as any },
    { step: "self_validate", status: "pending" as any },
  ];

  const report = (current: number, extraMsg?: string) => {
    if (extraMsg && steps[current]) {
      steps[current]!.message = extraMsg;
    }
    if (onProgress) {
      onProgress({ steps, currentStep: current });
    }
  };

  let accumulatedTokens = 0;

  // ── Step 1: Generate passage ────────────────────────────
  report(0);
  let passage: string;
  let title: string;
  try {
    const s1 = await step1GeneratePassage(client, input, onToken);
    passage = s1.passage;
    title = s1.title;
    accumulatedTokens += s1.tokensUsed;
    steps[0].status = "done";
    steps[0].message = `Generated: ${title}`;
    steps[0].output = passage;
    report(0);
  } catch (err: any) {
    steps[0].status = "error";
    steps[0].message = err.message ?? "Passage generation failed";
    throw new GenerationError(`Step 1 failed: ${err.message}`, { tokensUsed: accumulatedTokens });
  }

  // ── Step 2: Validate passage ────────────────────────────
  if (strategy === "full") {
    steps[1].status = "running";
    report(1);
    try {
      const s2 = await step2ValidatePassage(client, input, passage, onToken);
      accumulatedTokens += s2.tokensUsed;
      steps[1].status = s2.isValid ? "done" : "error";
      steps[1].message = s2.feedback;
      steps[1].output = JSON.stringify({ isValid: s2.isValid, feedback: s2.feedback }, null, 2);
      report(1);
    } catch (err: any) {
      steps[1].status = "error";
      steps[1].message = err.message ?? "Passage validation failed";
      throw new GenerationError(`Step 2 failed: ${err.message}`, { tokensUsed: accumulatedTokens });
    }
  } else {
    steps[1].status = "done";
    steps[1].message = "Skipped in lean strategy";
    report(1, steps[1].message);
  }

  return runAgenticQuestionPipeline({
    client,
    input,
    passage,
    steps,
    report,
    strategy,
    maxRegenAttempts,
    onToken,
    start,
    accumulatedTokens,
  });
}