// Match repeated codes by their unique descriptions when both sets agree.
const EstRowMatch = (() => {
  function identities(original, current, key) {
    const signature = (row) => JSON.stringify([row.Name || "", row.Size || "", row.Unite || ""]);
    const groups = (items) => {
      const result = new Map();
      items.forEach((row, index) => {
        const id = key(row, index),
          values = result.get(id) || [];
        values.push({ index, signature: signature(row) });
        result.set(id, values);
      });
      return result;
    };
    const oldGroups = groups(original),
      newGroups = groups(current),
      oldIds = [],
      currentIds = [];
    for (const id of new Set([...oldGroups.keys(), ...newGroups.keys()])) {
      const oldValues = oldGroups.get(id) || [],
        currentValues = newGroups.get(id) || [];
      if (oldValues.length <= 1 && currentValues.length <= 1) {
        const identity = JSON.stringify([id, "single"]);
        if (oldValues.length) oldIds[oldValues[0].index] = identity;
        if (currentValues.length) currentIds[currentValues[0].index] = identity;
        continue;
      }
      const counts = (values) => {
        const result = new Map();
        for (const value of values)
          result.set(value.signature, (result.get(value.signature) || 0) + 1);
        return result;
      };
      const oldCounts = counts(oldValues),
        currentCounts = counts(currentValues);
      const unique = (value) =>
        oldCounts.get(value.signature) === 1 && currentCounts.get(value.signature) === 1;
      for (const value of oldValues.filter(unique))
        oldIds[value.index] = JSON.stringify([id, "signature", value.signature]);
      for (const value of currentValues.filter(unique))
        currentIds[value.index] = JSON.stringify([id, "signature", value.signature]);
      const changedCount = oldValues.length !== currentValues.length;
      oldValues
        .filter((value) => !unique(value))
        .forEach((value, index) => {
          oldIds[value.index] = JSON.stringify([id, changedCount ? "old" : "remaining", index]);
        });
      currentValues
        .filter((value) => !unique(value))
        .forEach((value, index) => {
          currentIds[value.index] = JSON.stringify([id, changedCount ? "new" : "remaining", index]);
        });
    }
    return { original: oldIds, current: currentIds };
  }
  return { identities };
})();