import { describe, expect, it } from "vitest";
import { nextSign } from "@/journey/sign-controller";
import type { SignSnapshot } from "@/journey/types";

const passiveSample = (
  distanceVh: number,
  overrides: Partial<Parameters<typeof nextSign>[1]> = {},
): Parameters<typeof nextSign>[1] => ({
  source: "passive-scroll",
  deltaY: 10,
  viewportHeight: 100,
  crossedBoundaries: 0,
  candidateId: "profile",
  distanceVh,
  motionAllowed: true,
  ...overrides,
});

describe("forward-only sign latching", () => {
  it("latches a first eligible candidate at the exact approach boundary", () => {
    expect(nextSign(null, passiveSample(1.2))).toEqual({
      targetId: "profile",
      phase: "approach",
      progress: 0,
    });
  });

  it("maps the literal approach and pass ranges independently", () => {
    expect(nextSign(null, passiveSample(0.875))).toEqual({
      targetId: "profile",
      phase: "approach",
      progress: expect.closeTo(0.5, 14),
    });
    expect(nextSign(null, passiveSample(-0.05))).toEqual({
      targetId: "profile",
      phase: "pass",
      progress: 0.5,
    });
  });

  it("uses exact stabilized, pass, and completion boundaries", () => {
    const latched: SignSnapshot = {
      targetId: "profile",
      phase: "approach",
      progress: 0,
    };

    expect(nextSign(latched, passiveSample(0.55))).toEqual({
      targetId: "profile",
      phase: "stabilized",
      progress: 1,
    });
    expect(nextSign(latched, passiveSample(0.15))).toEqual({
      targetId: "profile",
      phase: "pass",
      progress: 0,
    });
    expect(nextSign(latched, passiveSample(-0.25))).toBeNull();
  });

  it("retains the one latched target while the semantic section advances", () => {
    const latched: SignSnapshot = {
      targetId: "profile",
      phase: "stabilized",
      progress: 1,
    };

    expect(
      nextSign(latched, passiveSample(0.1, { candidateId: "experience" })),
    ).toEqual({
      targetId: "profile",
      phase: "pass",
      progress: expect.closeTo(0.125, 14),
    });
  });

  it.each([
    ["reverse input", { deltaY: -2 }],
    ["zero-direction input", { deltaY: 0 }],
    ["explicit navigation", { source: "explicit-navigation" as const }],
    ["history restoration", { source: "history-restoration" as const }],
    ["initial positioning", { source: "initial" as const }],
    ["more than one activation boundary", { crossedBoundaries: 2 }],
    ["a jump over 0.75 viewport heights", { deltaY: 76 }],
    ["disabled motion", { motionAllowed: false }],
  ])("clears or suppresses signs for %s", (_label, overrides) => {
    const latched: SignSnapshot = {
      targetId: "profile",
      phase: "approach",
      progress: 0.5,
    };
    expect(nextSign(latched, passiveSample(0.5, overrides))).toBeNull();
  });

  it("does not latch before visibility or after a jump directly past completion", () => {
    expect(nextSign(null, passiveSample(1.20001))).toBeNull();
    expect(nextSign(null, passiveSample(-0.25))).toBeNull();
    expect(nextSign(null, passiveSample(-1))).toBeNull();
  });
});