package de.neitzel.fxdesigner.contracts;

import java.util.*;

/** One named undo transaction. All UTF-16 ranges address the same expected revision. */
public record EditBatch(long expectedRevision, String name, List<Replacement> replacements) {
  public record Replacement(int start, int end, String text) {
    public Replacement {
      if (start < 0 || end < start) throw new IllegalArgumentException("Invalid range");
      Objects.requireNonNull(text);
    }
  }

  public EditBatch {
    if (expectedRevision < 0) throw new IllegalArgumentException("Negative revision");
    if (name == null || name.isBlank()) throw new IllegalArgumentException("Missing command name");
    replacements = List.copyOf(replacements);
  }

  /** Validates every range before computing a result; never partially edits a host draft. */
  public String applyTo(DocumentSnapshot draft) {
    if (!draft.writable()) throw new IllegalStateException("Document is read-only");
    if (draft.revision() != expectedRevision)
      throw new ConcurrentModificationException("Stale document revision");
    var ordered = new ArrayList<>(replacements);
    ordered.sort(Comparator.comparingInt(Replacement::start));
    int previousEnd = -1;
    for (var r : ordered) {
      if (r.end() > draft.text().length() || r.start() < previousEnd)
        throw new IllegalArgumentException("Overlapping/out-of-bounds edits");
      previousEnd = r.end();
    }
    var result = new StringBuilder(draft.text());
    for (int i = ordered.size() - 1; i >= 0; i--) {
      var r = ordered.get(i);
      result.replace(r.start(), r.end(), r.text());
    }
    return result.toString();
  }
}