const fs = require("fs");
const path = require("path");
const { resolveData } = require("./paths");

class TrainingExporter {
  constructor({ feedback, corrections, outputDir }) {
    this.feedback = feedback;
    this.corrections = corrections;
    this.outputDir = outputDir || resolveData("exports");
  }

  export(format) {
    if (!["instruction", "dpo"].includes(format)) throw new Error("Unknown training export format.");
    const examples = approvedExamples(this.feedback.all(), this.corrections.all());
    const timestamp = new Date().toISOString().replace(/[:.]/g, "-");
    const filename = `lumi-ai-${format}-${timestamp}.jsonl`;
    const file = path.join(this.outputDir, filename);
    const rows = examples.map((entry) => format === "dpo"
      ? {
          prompt: entry.prompt,
          preferred_answer: entry.preferred_answer,
          rejected_answer: entry.rejected_answer
        }
      : {
          instruction: entry.prompt,
          input: "",
          output: entry.preferred_answer
        });
    fs.writeFileSync(file, rows.map((row) => JSON.stringify(row)).join("\n") + (rows.length ? "\n" : ""));
    return { file, filename: path.basename(file), count: rows.length, format };
  }
}

function approvedExamples(feedbackRows, correctionRows) {
  const byFeedback = new Map(
    correctionRows
      .filter((entry) => entry.approved && entry.corrected_answer)
      .map((entry) => [entry.source_feedback_id, entry])
  );
  return feedbackRows
    .filter((entry) => entry.export_approved && entry.status === "approved")
    .map((entry) => {
      const correction = byFeedback.get(entry.id);
      const preferred = correction?.corrected_answer || entry.optional_correction;
      if (!preferred) return null;
      return {
        prompt: entry.user_message,
        preferred_answer: preferred,
        rejected_answer: entry.assistant_answer
      };
    })
    .filter(Boolean);
}

module.exports = { TrainingExporter, approvedExamples };