// IMP-52 u6 — vitest coverage for restore-on-reopen helpers used by
// `Home.tsx` to layer persisted `user_overrides.json` payloads onto the
// in-memory `UserSelection` and `slidePlan`.
//
// Scope (Stage 2 unit u6 contract):
//   1) deriveUserOverridesKey(filename) — MDX-stem key derivation that
//      matches backend u2 fallback's `Path(args.mdx_path).stem`. Strips
//      `.mdx` case-insensitively; preserves everything else.
//   2) applyPersistedNonFrameOverrides(selection, persisted) — layers
//      layout / zone_geometries / zone_sections onto an existing selection.
//      Frames are NOT layered here (unit_id key requires slidePlan).
//      Foreign / unrecognized payloads degrade silently (no throw, no
//      partial mutation).
//   3) remapPersistedFramesToZoneFrames(slidePlan, framesByUnitId) —
//      remaps frames (unit_id → template_id) to zone_frames (region.id →
//      template_id). Stale unit_ids (no matching zone) drop silently;
//      zones without internal_regions[0] or without section_ids are
//      skipped without throwing.
//
// All helpers are pure; tests run in vitest's default node environment
// without RTL / jsdom. Home.tsx wiring sites (handleFileUpload pre-Generate
// seed + handleGenerate post-loadRun frame remap) are 1-line call sites that
// these helpers cover end-to-end.

import { describe, it, expect } from "vitest";
import type {
  LayoutPresetId,
  SlidePlan,
  UserSelection,
  Zone,
} from "../src/types/designAgent";
import {
  applyPersistedNonFrameOverrides,
  deriveUserOverridesKey,
  remapPersistedFramesToZoneFrames,
} from "../src/utils/slidePlanUtils";

// ─── Fixtures ───────────────────────────────────────────────────────────────

function makeSelection(overrides?: Partial<UserSelection["overrides"]>): UserSelection {
  return {
    selectedSectionId: null,
    selectedZoneId: null,
    selectedRegionId: null,
    overrides: {
      layout_preset: undefined,
      zone_frames: {},
      zone_sections: {},
      zone_sizes: {},
      zone_geometries: {},
      ...overrides,
    },
  };
}

function makeZone(
  partial: { id: string; zone_id: string; section_ids: string[]; region_id?: string },
): Zone {
  return {
    id: partial.id,
    zone_id: partial.zone_id,
    section_ids: partial.section_ids,
    position: { x: 0, y: 0, width: 1, height: 1 },
    internal_regions: [
      {
        id: partial.region_id ?? `${partial.id}-r0`,
        region_id: "region-single",
        role: "primary",
        content_type: "text_block",
        ratio_estimate: 1,
        content_unit_ids: [],
        frame_match_strategy: {
          kind: "frame_match",
          frame_id: null,
          display_strategy: "inline_full",
        },
        frame_candidates: [],
      },
    ],
  };
}

function makeSlidePlan(zones: Zone[], layout: LayoutPresetId = "single"): SlidePlan {
  return {
    id: "plan-1",
    title: "test plan",
    layout_preset: layout,
    zones,
  };
}

// ─── deriveUserOverridesKey ─────────────────────────────────────────────────

describe("deriveUserOverridesKey (IMP-52 u6)", () => {
  it("strips trailing .mdx", () => {
    expect(deriveUserOverridesKey("03__DX_BIM_value_chain.mdx")).toBe(
      "03__DX_BIM_value_chain",
    );
  });

  it("strips .MDX case-insensitively", () => {
    expect(deriveUserOverridesKey("04_demo.MDX")).toBe("04_demo");
    expect(deriveUserOverridesKey("05_intro.Mdx")).toBe("05_intro");
  });

  it("returns the filename unchanged when no .mdx suffix", () => {
    expect(deriveUserOverridesKey("03__DX_BIM_value_chain")).toBe(
      "03__DX_BIM_value_chain",
    );
    expect(deriveUserOverridesKey("notes.txt")).toBe("notes.txt");
  });

  it("only strips the final .mdx, preserves dots inside the stem", () => {
    expect(deriveUserOverridesKey("05.2_layer.mdx")).toBe("05.2_layer");
  });

  it("returns empty string for empty input", () => {
    expect(deriveUserOverridesKey("")).toBe("");
  });

  it("matches backend Path(args.mdx_path).stem for the canonical demo MDXs", () => {
    // These are the three canonical samples loaded by /api/sample-mdx; the
    // key on both ends must agree so a write from frontend (PUT) is found
    // by backend (u2 fallback on next pipeline run).
    expect(deriveUserOverridesKey("03_demo.mdx")).toBe("03_demo");
    expect(deriveUserOverridesKey("04_demo.mdx")).toBe("04_demo");
    expect(deriveUserOverridesKey("05_demo.mdx")).toBe("05_demo");
  });
});

// ─── applyPersistedNonFrameOverrides ────────────────────────────────────────

describe("applyPersistedNonFrameOverrides (IMP-52 u6)", () => {
  it("layers layout / zone_geometries / zone_sections", () => {
    const sel = makeSelection();
    const persisted = {
      layout: "horizontal-2",
      zone_geometries: { top: { x: 0, y: 0, w: 1, h: 0.4 } },
      zone_sections: { top: ["03-1"], bottom: ["03-2"] },
    } as const;
    const next = applyPersistedNonFrameOverrides(sel, persisted);
    expect(next.overrides.layout_preset).toBe("horizontal-2");
    expect(next.overrides.zone_geometries).toEqual({
      top: { x: 0, y: 0, w: 1, h: 0.4 },
    });
    expect(next.overrides.zone_sections).toEqual({
      top: ["03-1"],
      bottom: ["03-2"],
    });
  });

  it("does NOT layer frames (frames need post-loadRun remap)", () => {
    const sel = makeSelection({ zone_frames: { "r-existing": "tpl-existing" } });
    const persisted = {
      frames: { "03-1+03-2": "tpl-persisted" },
    };
    const next = applyPersistedNonFrameOverrides(sel, persisted);
    // zone_frames is untouched here; the post-loadRun remap step owns it.
    expect(next.overrides.zone_frames).toEqual({ "r-existing": "tpl-existing" });
  });

  it("rejects layout values outside the 8 known preset ids", () => {
    const sel = makeSelection({ layout_preset: "single" });
    const next = applyPersistedNonFrameOverrides(sel, {
      layout: "rogue-layout" as unknown as string,
    });
    // Stays at the original — preset whitelist guards against hand-edited
    // files or future schema drift.
    expect(next.overrides.layout_preset).toBe("single");
  });

  it("ignores zone_geometries when the payload axis is an array", () => {
    const sel = makeSelection({ zone_geometries: { top: { x: 0, y: 0, w: 1, h: 0.5 } } });
    const next = applyPersistedNonFrameOverrides(sel, {
      zone_geometries: [] as unknown as Record<string, { x: number; y: number; w: number; h: number }>,
    });
    expect(next.overrides.zone_geometries).toEqual({
      top: { x: 0, y: 0, w: 1, h: 0.5 },
    });
  });

  it("returns the selection unchanged when persisted is null / undefined / non-object", () => {
    const sel = makeSelection({ layout_preset: "single" });
    expect(applyPersistedNonFrameOverrides(sel, null)).toEqual(sel);
    expect(applyPersistedNonFrameOverrides(sel, undefined)).toEqual(sel);
  });

  it("returns the selection unchanged when persisted is empty {}", () => {
    const sel = makeSelection({ layout_preset: "single" });
    const next = applyPersistedNonFrameOverrides(sel, {});
    expect(next.overrides.layout_preset).toBe("single");
    expect(next.overrides.zone_geometries).toEqual({});
    expect(next.overrides.zone_sections).toEqual({});
  });

  it("returns a NEW selection object (no mutation of input)", () => {
    const sel = makeSelection();
    const next = applyPersistedNonFrameOverrides(sel, { layout: "vertical-2" });
    expect(next).not.toBe(sel);
    expect(next.overrides).not.toBe(sel.overrides);
    // Input still pristine.
    expect(sel.overrides.layout_preset).toBeUndefined();
  });
});

// ─── remapPersistedFramesToZoneFrames ───────────────────────────────────────

describe("remapPersistedFramesToZoneFrames (IMP-52 u6)", () => {
  it("maps unit_id (section_ids joined by +) to region.id", () => {
    const plan = makeSlidePlan([
      makeZone({ id: "z-top", zone_id: "top", section_ids: ["03-1"], region_id: "r-top" }),
      makeZone({ id: "z-bot", zone_id: "bottom", section_ids: ["03-2", "03-3"], region_id: "r-bot" }),
    ]);
    const remapped = remapPersistedFramesToZoneFrames(plan, {
      "03-1": "tpl-a",
      "03-2+03-3": "tpl-b",
    });
    expect(remapped).toEqual({
      "r-top": "tpl-a",
      "r-bot": "tpl-b",
    });
  });

  it("silently drops persisted entries whose unit_id matches no zone", () => {
    const plan = makeSlidePlan([
      makeZone({ id: "z-top", zone_id: "top", section_ids: ["03-1"], region_id: "r-top" }),
    ]);
    const remapped = remapPersistedFramesToZoneFrames(plan, {
      "03-1": "tpl-a",
      "stale-section-id": "tpl-stale", // user changed zone_sections between sessions
    });
    expect(remapped).toEqual({ "r-top": "tpl-a" });
  });

  it("returns {} when slidePlan is null / undefined", () => {
    expect(remapPersistedFramesToZoneFrames(null, { "03-1": "tpl-a" })).toEqual({});
    expect(remapPersistedFramesToZoneFrames(undefined, { "03-1": "tpl-a" })).toEqual({});
  });

  it("returns {} when framesByUnitId is null / undefined / {}", () => {
    const plan = makeSlidePlan([
      makeZone({ id: "z-top", zone_id: "top", section_ids: ["03-1"], region_id: "r-top" }),
    ]);
    expect(remapPersistedFramesToZoneFrames(plan, null)).toEqual({});
    expect(remapPersistedFramesToZoneFrames(plan, undefined)).toEqual({});
    expect(remapPersistedFramesToZoneFrames(plan, {})).toEqual({});
  });

  it("skips zones with empty section_ids (no unit_id to derive)", () => {
    const plan = makeSlidePlan([
      makeZone({ id: "z-empty", zone_id: "empty", section_ids: [], region_id: "r-empty" }),
      makeZone({ id: "z-top", zone_id: "top", section_ids: ["03-1"], region_id: "r-top" }),
    ]);
    const remapped = remapPersistedFramesToZoneFrames(plan, {
      "": "tpl-should-not-match-empty-join",
      "03-1": "tpl-a",
    });
    expect(remapped).toEqual({ "r-top": "tpl-a" });
  });

  it("skips zones without internal_regions[0]", () => {
    const plan: SlidePlan = {
      id: "plan-x",
      title: "no regions",
      layout_preset: "single",
      zones: [
        {
          id: "z-bare",
          zone_id: "bare",
          section_ids: ["03-1"],
          position: { x: 0, y: 0, width: 1, height: 1 },
          internal_regions: [],
        },
      ],
    };
    expect(remapPersistedFramesToZoneFrames(plan, { "03-1": "tpl-a" })).toEqual({});
  });

  it("ignores persisted entries with empty / non-string template_id", () => {
    const plan = makeSlidePlan([
      makeZone({ id: "z-top", zone_id: "top", section_ids: ["03-1"], region_id: "r-top" }),
    ]);
    const remapped = remapPersistedFramesToZoneFrames(plan, {
      "03-1": "" as unknown as string,
    });
    expect(remapped).toEqual({});
  });

  it("preserves the user-selected template even when slidePlan layout would imply a different default", () => {
    // Backend u2 fallback should already have applied the user's frame
    // override via CLI args, but if the plan's default frame_match_strategy
    // disagrees, the post-loadRun remap still surfaces the user's choice
    // for the SlideCanvas override-vs-default preview indicator.
    const plan = makeSlidePlan([
      makeZone({ id: "z-top", zone_id: "top", section_ids: ["03-1"], region_id: "r-top" }),
    ]);
    const remapped = remapPersistedFramesToZoneFrames(plan, {
      "03-1": "user-chosen-tpl",
    });
    expect(remapped["r-top"]).toBe("user-chosen-tpl");
  });
});