/**
 * RTO.27F — Primary lifecycle surface invariant
 *
 * Tests that exactly one primary surface renders in every meaningful state:
 * no zero, no two.  Exercises the exported predicates from
 * scenario-form.jsx directly to avoid SSR/React-Testing-Library complications.
 */

import { describe, it, expect } from "vitest";
import { hasValidInvestigationContext, derivePrimarySurface } from "@/components/scenario-form";

/* ── Helpers ─────────────────────────────────────────────────────── */

const EMPTY_RESULT = null;
const RESULT_WITH_GRAPH = { situationGraph: {}, selectedQuestion: "q1" };
const SCENARIO_EMPTY = "";
const SCENARIO_SET = "Some situation description";

/* ── hasValidInvestigationContext tests ─────────────────────────── */

describe("hasValidInvestigationContext", () => {
  it("rejects idle + no result + empty scenario", () => {
    expect(hasValidInvestigationContext(EMPTY_RESULT, "idle", SCENARIO_EMPTY)).toBe(false);
  });

  it("rejects loading state", () => {
    expect(hasValidInvestigationContext(EMPTY_RESULT, "loading", SCENARIO_SET)).toBe(false);
  });

  it("accepts result with situationGraph", () => {
    expect(hasValidInvestigationContext(RESULT_WITH_GRAPH, "success", SCENARIO_EMPTY)).toBe(true);
  });

  it("accepts success + non-empty scenario (session restoration)", () => {
    expect(hasValidInvestigationContext(EMPTY_RESULT, "success", SCENARIO_SET)).toBe(true);
  });

  it("rejects success + empty scenario (no investigation data)", () => {
    expect(hasValidInvestigationContext(EMPTY_RESULT, "success", SCENARIO_EMPTY)).toBe(false);
  });

  it("rejects error state even with graph (graph is valid but surface is ERROR)", () => {
    // Note: hasGraph returns true — the derivePrimarySurface function handles this by routing to ERROR_SURFACE first.
    expect(hasValidInvestigationContext(RESULT_WITH_GRAPH, "error", SCENARIO_SET)).toBe(true);
  });

  it("rejects false scenario input (empty string)", () => {
    expect(hasValidInvestigationContext(EMPTY_RESULT, "success", "")).toBe(false);
  });

  it("rejects whitespace-only scenario", () => {
    expect(hasValidInvestigationContext(EMPTY_RESULT, "success", "   ")).toBe(false);
  });
});

/* ── derivePrimarySurface tests (7 required cases) ─────────────── */

describe("derivePrimarySurface — CASE 1: idle / no result / experiment=false", () => {
  it("returns SCENARIO_ENTRY", () => {
    const surface = derivePrimarySurface(EMPTY_RESULT, "idle", false, SCENARIO_EMPTY);
    expect(surface).toBe("SCENARIO_ENTRY");
    expect(surface).not.toBeNull();
    expect(surface).not.toBe("");
  });
});

describe("derivePrimarySurface — CASE 2: idle / no result / experiment=true (stale flag)", () => {
  it("returns SCENARIO_ENTRY (not blank) — this is the RTO.27F critical fix", () => {
    const surface = derivePrimarySurface(EMPTY_RESULT, "idle", true, SCENARIO_EMPTY);
    expect(surface).toBe("SCENARIO_ENTRY");
    expect(surface).not.toBeNull();
    expect(surface).not.toBe("");
  });
});

describe("derivePrimarySurface — CASE 3: valid investigation / experiment=true / branch selected", () => {
  it("returns EXPERIMENT_NOTEBOOK when a branch is active", () => {
    const surface = derivePrimarySurface(RESULT_WITH_GRAPH, "success", true, SCENARIO_SET, "branch-a");
    expect(surface).toBe("EXPERIMENT_NOTEBOOK");
    expect(surface).not.toBeNull();
    expect(surface).not.toBe("");
  });
});

describe("derivePrimarySurface — RTO.28A: branch-selection surface", () => {
  it("returns BRANCH_SELECTION when valid investigation exists but activeBranchId is null", () => {
    const surface = derivePrimarySurface(RESULT_WITH_GRAPH, "success", true, SCENARIO_SET, null);
    expect(surface).toBe("BRANCH_SELECTION");
    expect(surface).not.toBeNull();
    expect(surface).not.toBe("");
  });

  it("returns EXPERIMENT_NOTEBOOK when valid investigation exists and activeBranchId is set", () => {
    const surface = derivePrimarySurface(RESULT_WITH_GRAPH, "success", true, SCENARIO_SET, "branch-a");
    expect(surface).toBe("EXPERIMENT_NOTEBOOK");
    expect(surface).not.toBeNull();
    expect(surface).not.toBe("");
  });

  it("returns EXPERIMENT_NOTEBOOK when valid investigation exists and activeBranchId is branch-b", () => {
    const surface = derivePrimarySurface(RESULT_WITH_GRAPH, "success", true, SCENARIO_SET, "branch-b");
    expect(surface).toBe("EXPERIMENT_NOTEBOOK");
    expect(surface).not.toBeNull();
    expect(surface).not.toBe("");
  });
});

describe("derivePrimarySurface — CASE 4: valid investigation / experiment=false", () => {
  it("returns NORMAL_WORKSPACE", () => {
    const surface = derivePrimarySurface(RESULT_WITH_GRAPH, "success", false, SCENARIO_SET);
    expect(surface).toBe("NORMAL_WORKSPACE");
    expect(surface).not.toBeNull();
    expect(surface).not.toBe("");
  });
});

describe("derivePrimarySurface — CASE 5: loading", () => {
  it("returns LOADING regardless of other flags", () => {
    const surface = derivePrimarySurface(RESULT_WITH_GRAPH, "loading", true, SCENARIO_SET);
    expect(surface).toBe("LOADING");
    expect(surface).not.toBeNull();

    // Even with empty scenario or no graph — loading always wins
    const surface2 = derivePrimarySurface(null, "loading", false, "");
    expect(surface2).toBe("LOADING");
    expect(surface2).not.toBeNull();
  });
});

describe("derivePrimarySurface — CASE 6: error / valid context", () => {
  it("returns ERROR_SURFACE when graph exists", () => {
    const surface = derivePrimarySurface(RESULT_WITH_GRAPH, "error", false, SCENARIO_SET);
    expect(surface).toBe("ERROR_SURFACE");
    expect(surface).not.toBeNull();
  });

  it("returns ERROR_SURFACE even with no graph (safe fallback)", () => {
    const surface = derivePrimarySurface(null, "error", false, SCENARIO_SET);
    expect(surface).toBe("ERROR_SURFACE");
    expect(surface).not.toBeNull();
  });
});

describe("derivePrimarySurface — CASE 7: partial/stale restored session", () => {
  it("returns SCENARIO_ENTRY when no graph and idle (stale experiment flag)", () => {
    const surface = derivePrimarySurface(EMPTY_RESULT, "idle", true, SCENARIO_EMPTY);
    expect(surface).toBe("SCENARIO_ENTRY");
    expect(surface).not.toBeNull();
  });

  it("returns BRANCH_SELECTION when session has scenario + success (valid context, no branch)", () => {
    const surface = derivePrimarySurface(EMPTY_RESULT, "success", true, SCENARIO_SET);
    expect(surface).toBe("BRANCH_SELECTION");
    expect(surface).not.toBeNull();
  });

  it("returns SCENARIO_ENTRY for stale experiment preference without any session data", () => {
    const surface = derivePrimarySurface(EMPTY_RESULT, "idle", true, "");
    expect(surface).toBe("SCENARIO_ENTRY");
    expect(surface).not.toBeNull();
  });
});

/* ── Exhaustive invariant: every state maps to exactly one surface ─ */

describe("PRIMARY_SURFACE_COUNT — exhaustive invariant (zero allowed, two forbidden)", () => {
  const testCases = [
    // idle variants
    { result: null, status: "idle", exp: false, scenario: "", ab: null, expected: "SCENARIO_ENTRY" },
    { result: null, status: "idle", exp: true, scenario: "", ab: null, expected: "SCENARIO_ENTRY" },
    { result: null, status: "idle", exp: false, scenario: "x", ab: null, expected: "SCENARIO_ENTRY" },
    // loading variants
    { result: null, status: "loading", exp: false, scenario: "", ab: null, expected: "LOADING" },
    { result: null, status: "loading", exp: true, scenario: "x", ab: null, expected: "LOADING" },
    { result: RESULT_WITH_GRAPH, status: "loading", exp: false, scenario: "x", ab: null, expected: "LOADING" },
    // error variants
    { result: null, status: "error", exp: false, scenario: "x", ab: null, expected: "ERROR_SURFACE" },
    { result: RESULT_WITH_GRAPH, status: "error", exp: true, scenario: "x", ab: null, expected: "ERROR_SURFACE" },
    // success — no graph, empty scenario (no valid context)
    { result: null, status: "success", exp: false, scenario: "", ab: null, expected: "SCENARIO_ENTRY" },
    { result: null, status: "success", exp: true, scenario: "", ab: null, expected: "SCENARIO_ENTRY" },
    // success — no graph, non-empty scenario (session restored without graph)
    { result: null, status: "success", exp: false, scenario: "x", ab: null, expected: "NORMAL_WORKSPACE" },
    { result: null, status: "success", exp: true, scenario: "x", ab: null, expected: "BRANCH_SELECTION" },
    // success — with graph, no branch → BRANCH_SELECTION
    { result: RESULT_WITH_GRAPH, status: "success", exp: true, scenario: "x", ab: null, expected: "BRANCH_SELECTION" },
    // success — with graph, branch-a selected → EXPERIMENT_NOTEBOOK
    { result: RESULT_WITH_GRAPH, status: "success", exp: true, scenario: "x", ab: "branch-a", expected: "EXPERIMENT_NOTEBOOK" },
    // success — with graph, branch-b selected → EXPERIMENT_NOTEBOOK
    { result: RESULT_WITH_GRAPH, status: "success", exp: true, scenario: "x", ab: "branch-b", expected: "EXPERIMENT_NOTEBOOK" },
    // success — with graph, experiment=false (production)
    { result: RESULT_WITH_GRAPH, status: "success", exp: false, scenario: "x", ab: null, expected: "NORMAL_WORKSPACE" },
  ];

  for (const tc of testCases) {
    it(
      `${tc.status}|exp=${tc.exp}|graph=${!!tc.result?.situationGraph}|ab=${tc.ab}|"${tc.scenario}" → ${tc.expected}`,
      () => {
        const surface = derivePrimarySurface(tc.result, tc.status, tc.exp, tc.scenario, tc.ab);
        expect(surface).toBe(tc.expected);
        // The invariant: exactly one surface, never null/undefined/blank
        expect(surface).not.toBeNull();
        expect(surface).not.toBe("");
        expect(surface).toBeDefined();
      }
    );
  }
});