const http = require("http");
const fs = require("fs");
const path = require("path");
const XLSX = require("xlsx");
const formidable = require("formidable");

const PORT = process.env.PORT || 3000;

function readExcelFile(filePath) {
  const wb = XLSX.readFile(filePath);
  const sheets = {};
  wb.SheetNames.forEach(function (name) {
    const data = XLSX.utils.sheet_to_json(wb.Sheets[name], { header: 1, defval: "" });
    sheets[name] = data;
  });
  return { name: path.basename(filePath), sheets: sheets, sheetNames: wb.SheetNames };
}

function compareFiles(fileA, fileB) {
  const a = readExcelFile(fileA);
  const b = readExcelFile(fileB);
  var report = [];
  report.push("Сравнение: " + a.name + "  vs  " + b.name);
  report.push("=".repeat(60));
  report.push("");

  var allSheets = Array.from(new Set(a.sheetNames.concat(b.sheetNames)));

  allSheets.forEach(function (sheetName) {
    var inA = a.sheetNames.indexOf(sheetName) >= 0;
    var inB = b.sheetNames.indexOf(sheetName) >= 0;

    if (!inA) {
      report.push("Лист «" + sheetName + "»: есть ТОЛЬКО во втором файле (" + b.name + ")");
      report.push("  Строк: " + (b.sheets[sheetName] ? b.sheets[sheetName].length : 0));
      report.push("");
      return;
    }
    if (!inB) {
      report.push("Лист «" + sheetName + "»: есть ТОЛЬКО в первом файле (" + a.name + ")");
      report.push("  Строк: " + (a.sheets[sheetName] ? a.sheets[sheetName].length : 0));
      report.push("");
      return;
    }

    var rowsA = a.sheets[sheetName];
    var rowsB = b.sheets[sheetName];
    var maxRows = Math.max(rowsA.length, rowsB.length);
    var maxCols = 0;
    rowsA.forEach(function (r) { if (r.length > maxCols) maxCols = r.length; });
    rowsB.forEach(function (r) { if (r.length > maxCols) maxCols = r.length; });

    var changes = [];
    var added = 0, removed = 0, modified = 0;

    for (var i = 0; i < maxRows; i++) {
      var rowA = rowsA[i] || [];
      var rowB = rowsB[i] || [];
      var maxC = Math.max(rowA.length, rowB.length);
      for (var j = 0; j < maxC; j++) {
        var valA = String(rowA[j] != null ? rowA[j] : "").trim();
        var valB = String(rowB[j] != null ? rowB[j] : "").trim();
        if (valA === valB) continue;
        var colLetter = String.fromCharCode(65 + (j % 26));
        if (j >= 26) colLetter = String.fromCharCode(64 + Math.floor(j / 26)) + colLetter;
        var cellRef = colLetter + (i + 1);
        if (valA === "" && valB !== "") {
          changes.push("  + " + cellRef + ": «" + valB + "»");
          added++;
        } else if (valA !== "" && valB === "") {
          changes.push("  - " + cellRef + ": было «" + valA + "»");
          removed++;
        } else {
          changes.push("  ~ " + cellRef + ": «" + valA + "» → «" + valB + "»");
          modified++;
        }
      }
    }

    report.push("Лист «" + sheetName + "» — " + rowsA.length + "×" + rowsA[0].length + " vs " + rowsB.length + "×" + (rowsB[0] ? rowsB[0].length : 0));
    if (changes.length === 0) {
      report.push("  Отличий нет.");
    } else {
      report.push("  Изменений: " + (added + removed + modified) + " (+" + added + " / -" + removed + " / ~" + modified + ")");
      report.push("");
      report.push.apply(report, changes);
    }
    report.push("");
  });

  return {
    fileNameA: a.name,
    fileNameB: b.name,
    sheetsA: a.sheetNames.length,
    sheetsB: b.sheetNames.length,
    report: report.join("\n")
  };
}

http.createServer(function (req, res) {
  if (req.method === "POST" && req.url === "/api/compare") {
    var form = formidable({ uploadDir: __dirname, keepExtensions: true, maxFileSize: 100 * 1024 * 1024 });
    form.parse(req, function (err, fields, files) {
      if (err) {
        res.writeHead(400, { "Content-Type": "application/json" });
        return res.end(JSON.stringify({ ok: false, error: "Ошибка загрузки: " + err.message }));
      }
      var f1 = files.file1 && files.file1[0];
      var f2 = files.file2 && files.file2[0];
      if (!f1 || !f2) {
        res.writeHead(400, { "Content-Type": "application/json" });
        return res.end(JSON.stringify({ ok: false, error: "Загрузите оба файла" }));
      }
      try {
        var result = compareFiles(f1.filepath, f2.filepath);
        try { fs.unlinkSync(f1.filepath); } catch (e) {}
        try { fs.unlinkSync(f2.filepath); } catch (e) {}
        res.writeHead(200, { "Content-Type": "application/json" });
        res.end(JSON.stringify({ ok: true, data: result }));
      } catch (e) {
        res.writeHead(500, { "Content-Type": "application/json" });
        res.end(JSON.stringify({ ok: false, error: "Ошибка чтения файла: " + e.message }));
      }
    });
    return;
  }

  if (req.method === "POST" && req.url === "/api/analyze") {
    var form2 = formidable({ uploadDir: __dirname, keepExtensions: true, maxFileSize: 100 * 1024 * 1024 });
    form2.parse(req, function (err, fields, files) {
      if (err) {
        res.writeHead(400, { "Content-Type": "application/json" });
        return res.end(JSON.stringify({ ok: false, error: "Ошибка загрузки: " + err.message }));
      }
      var f = files.file && files.file[0];
      if (!f) {
        res.writeHead(400, { "Content-Type": "application/json" });
        return res.end(JSON.stringify({ ok: false, error: "Загрузите файл" }));
      }
      try {
        var wb = XLSX.readFile(f.filepath);
        var analysis = [];
        analysis.push("Анализ файла: " + path.basename(f.filepath));
        analysis.push("=".repeat(60));
        analysis.push("Листов: " + wb.SheetNames.length);
        analysis.push("Имена листов: " + wb.SheetNames.join(", "));
        analysis.push("");

        wb.SheetNames.forEach(function (name) {
          var data = XLSX.utils.sheet_to_json(wb.Sheets[name], { header: 1, defval: "" });
          var rows = data.length;
          var cols = 0;
          data.forEach(function (r) { if (r.length > cols) cols = r.length; });
          var nonEmpty = 0;
          data.forEach(function (r) {
            r.forEach(function (c) { if (String(c).trim() !== "") nonEmpty++; });
          });
          analysis.push("Лист «" + name + "»:");
          analysis.push("  Размер: " + rows + " строк × " + cols + " столбцов");
          analysis.push("  Заполненных ячеек: " + nonEmpty);
          if (rows > 0 && cols > 0) {
            analysis.push("  Заголовок (строка 1): " + data[0].map(function (c) { return String(c).trim(); }).filter(Boolean).join(" | "));
          }
          analysis.push("");
        });

        try { fs.unlinkSync(f.filepath); } catch (e) {}
        res.writeHead(200, { "Content-Type": "application/json" });
        res.end(JSON.stringify({ ok: true, data: { report: analysis.join("\n") } }));
      } catch (e) {
        res.writeHead(500, { "Content-Type": "application/json" });
        res.end(JSON.stringify({ ok: false, error: "Ошибка чтения файла: " + e.message }));
      }
    });
    return;
  }

  var file = req.url === "/" ? "/index.html" : req.url.split("?")[0];
  var full = path.join(__dirname, file);
  if (full.startsWith(__dirname) && fs.existsSync(full) && fs.statSync(full).isFile()) {
    var ext = path.extname(full);
    var type = ext === ".css" ? "text/css" : ext === ".js" ? "application/javascript" : "text/html";
    res.writeHead(200, { "Content-Type": type + "; charset=utf-8" });
    return res.end(fs.readFileSync(full));
  }
  res.writeHead(404);
  res.end("Not found");
}).listen(PORT, function () {
  console.log("Сервер на порту " + PORT);
});