const DRIVER_COLUMNS = {
  id: ["id", "driver_id", "forar_id"],
  name: ["name", "namn", "driver", "driver_name", "forare", "forarnamn"],
  className: ["class", "klass", "class_name", "klassnamn", "class_id", "klass_id"],
  brand: ["brand", "marke", "team", "sponsor", "model", "modell"],
  transponder: ["transponder", "transponder_id", "transpondernummer", "ponder"],
  speechName: ["spoken_name", "speech_name", "talnamn", "upplasningsnamn"],
  club: ["club", "klubb"],
  country: ["country", "land", "nation"],
  profileId: ["profile_id", "training_profile_id", "profil_id", "traningsprofil_id"],
};

const CAR_COLUMNS = {
  id: ["id", "car_id", "bil_id"],
  name: ["name", "namn", "car", "car_name", "bil", "bilnamn"],
  brand: ["brand", "marke", "model", "modell", "chassis", "chassi"],
  transponder: ["transponder", "transponder_id", "transpondernummer", "ponder"],
};

function normalizeHeader(value) {
  return String(value || "")
    .replace(/^\uFEFF/, "")
    .normalize("NFD")
    .replace(/[\u0300-\u036f]/g, "")
    .trim()
    .toLowerCase()
    .replace(/[^a-z0-9]+/g, "_")
    .replace(/^_+|_+$/g, "");
}

function normalizeMatch(value) {
  return String(value || "").trim().toLocaleLowerCase().replace(/\s+/g, " ");
}

function countDelimiter(line, delimiter) {
  let quoted = false;
  let count = 0;
  for (let index = 0; index < line.length; index += 1) {
    if (line[index] === '"') {
      if (quoted && line[index + 1] === '"') index += 1;
      else quoted = !quoted;
    } else if (!quoted && line[index] === delimiter) {
      count += 1;
    }
  }
  return count;
}

function detectDelimiter(text) {
  const firstLine = String(text || "").split(/\r?\n/).find((line) => line.trim()) || "";
  return [",", ";", "\t"]
    .map((delimiter) => ({ delimiter, count: countDelimiter(firstLine, delimiter) }))
    .sort((left, right) => right.count - left.count)[0]?.delimiter || ",";
}

export function parseCsvRows(text) {
  const source = String(text || "");
  if (!source.trim()) throw new Error("CSV file is empty");
  const delimiter = detectDelimiter(source);
  const rows = [];
  let row = [];
  let field = "";
  let quoted = false;

  for (let index = 0; index < source.length; index += 1) {
    const char = source[index];
    if (quoted) {
      if (char === '"' && source[index + 1] === '"') {
        field += '"';
        index += 1;
      } else if (char === '"') {
        quoted = false;
      } else {
        field += char;
      }
    } else if (char === '"') {
      quoted = true;
    } else if (char === delimiter) {
      row.push(field.trim());
      field = "";
    } else if (char === "\n" || char === "\r") {
      if (char === "\r" && source[index + 1] === "\n") index += 1;
      row.push(field.trim());
      if (row.some((value) => value)) rows.push(row);
      row = [];
      field = "";
    } else {
      field += char;
    }
  }
  if (quoted) throw new Error("CSV file has an unclosed quoted field");
  row.push(field.trim());
  if (row.some((value) => value)) rows.push(row);
  if (rows.length < 2) throw new Error("CSV file has no data rows");

  const headers = rows[0].map(normalizeHeader);
  if (!headers.some(Boolean)) throw new Error("CSV file has no header row");
  return rows.slice(1).map((values, rowIndex) => ({
    rowNumber: rowIndex + 2,
    values: Object.fromEntries(headers.map((header, index) => [header, String(values[index] || "").trim()])),
  }));
}

function readColumn(record, aliases) {
  for (const alias of aliases) {
    const value = record[normalizeHeader(alias)];
    if (value != null && String(value).trim()) return String(value).trim();
  }
  return "";
}

function readMappedRecord(record, columns) {
  return Object.fromEntries(Object.entries(columns).map(([key, aliases]) => [key, readColumn(record, aliases)]));
}

function mergeNonEmpty(current, incoming, fields) {
  const next = { ...current };
  fields.forEach((field) => {
    if (String(incoming[field] ?? "").trim()) next[field] = incoming[field];
  });
  return next;
}

function resolveClass(classValue, classes, uid) {
  const value = String(classValue || "").trim();
  if (!value) return "";
  const existing = classes.find((item) => String(item.id || "") === value || normalizeMatch(item.name) === normalizeMatch(value));
  if (existing) return existing.id;
  const created = { id: uid("class"), name: value };
  classes.push(created);
  return created.id;
}

export function importDriversCsv(text, context) {
  const classes = (context.classes || []).map((item) => ({ ...item }));
  const drivers = (context.drivers || []).map((item) => ({ ...item }));
  const uid = context.uid;
  const parsedRows = parseCsvRows(text);
  let added = 0;
  let updated = 0;
  let skipped = 0;

  parsedRows.forEach(({ values }) => {
    const row = readMappedRecord(values, DRIVER_COLUMNS);
    if (!row.name) {
      skipped += 1;
      return;
    }
    const classId = resolveClass(row.className, classes, uid);
    const normalizedName = normalizeMatch(row.name);
    const byNameAndClass = drivers.filter((item) => (
      normalizeMatch(item.name) === normalizedName && (!classId || String(item.classId || "") === classId)
    ));
    const existing = drivers.find((item) => row.id && String(item.id || "") === row.id)
      || drivers.find((item) => row.transponder && String(item.transponder || "") === row.transponder)
      || (byNameAndClass.length === 1 ? byNameAndClass[0] : null);
    const samePerson = drivers.find((item) => normalizeMatch(item.name) === normalizedName && item.profileId);
    const incoming = {
      id: row.id || uid("driver"),
      name: row.name,
      classId,
      brand: row.brand,
      transponder: row.transponder,
      speechName: row.speechName,
      club: row.club,
      country: row.country,
      profileId: row.profileId || samePerson?.profileId || uid("profile"),
    };
    if (existing) {
      const index = drivers.indexOf(existing);
      drivers[index] = mergeNonEmpty(existing, incoming, ["name", "classId", "brand", "transponder", "speechName", "club", "country", "profileId"]);
      updated += 1;
    } else {
      drivers.push(incoming);
      added += 1;
    }
  });

  return { classes, drivers, added, updated, skipped };
}

export function importCarsCsv(text, context) {
  const cars = (context.cars || []).map((item) => ({ ...item }));
  const uid = context.uid;
  const parsedRows = parseCsvRows(text);
  let added = 0;
  let updated = 0;
  let skipped = 0;

  parsedRows.forEach(({ values }) => {
    const row = readMappedRecord(values, CAR_COLUMNS);
    if (!row.name) {
      skipped += 1;
      return;
    }
    const matchingNames = cars.filter((item) => normalizeMatch(item.name) === normalizeMatch(row.name));
    const existing = cars.find((item) => row.id && String(item.id || "") === row.id)
      || cars.find((item) => row.transponder && String(item.transponder || "") === row.transponder)
      || (matchingNames.length === 1 ? matchingNames[0] : null);
    const incoming = {
      id: row.id || uid("car"),
      name: row.name,
      brand: row.brand,
      transponder: row.transponder,
    };
    if (existing) {
      const index = cars.indexOf(existing);
      cars[index] = mergeNonEmpty(existing, incoming, ["name", "brand", "transponder"]);
      updated += 1;
    } else {
      cars.push(incoming);
      added += 1;
    }
  });

  return { cars, added, updated, skipped };
}