import { describe, test, expect } from "vitest";
import { decorationPlan } from "../src/trackChangesModel";

describe("decorationPlan (INV-49)", () => {
  test("derives insertion ranges + deletion hints from original→replacement", () => {
    // anchorStart 10; original 'the brown fox' → 'the red fox'
    const plan = decorationPlan(10, "the brown fox", "the red fox");
    // one changed run: 'brown ' → 'red ' (word-level); insertion 'red ' tinted,
    // deletion hint 'brown ' shown at the run start.
    expect(plan.insertions.length).toBeGreaterThan(0);
    expect(plan.deletions.length).toBeGreaterThan(0);
    // insertion offsets are in buffer coords (>= anchorStart) and lie within the applied text
    for (const ins of plan.insertions) {
      expect(ins.start).toBeGreaterThanOrEqual(10);
      expect(ins.end).toBeLessThanOrEqual(10 + "the red fox".length);
    }
    // a deletion hint carries the struck original text at a buffer offset
    expect(plan.deletions[0].text).toContain("brown");
  });

  test("pure insertion (no deletion) yields an insertion range and no deletion hint", () => {
    // 'hello' → 'hello world': ' world' is a pure word-level insertion (no removed tokens)
    const plan = decorationPlan(0, "hello", "hello world");
    expect(plan.insertions.length).toBe(1);
    expect(plan.deletions.length).toBe(0);
  });
});