import type { FileNode, FsSlice, SaveV1 } from "./types";

import { DESKTOP_ID, baseNodes, initialFsSlice } from "./state";

/** Playable levels are 0..3; 4 means finished. */
export const LAST_PLAYABLE = 3;

function withDesktop(children: Omit<FileNode, "parentId">[]): FileNode[] {
  const nodes = baseNodes();
  for (const c of children) {
    nodes.push({ ...c, parentId: DESKTOP_ID });
  }
  return nodes;
}

function level0Nodes(): FileNode[] {
  return withDesktop([
    { id: "fld-docs", name: "Documents", kind: "folder" },
    { id: "fld-games", name: "Games", kind: "folder" },
    { id: "file-readme", name: "READ_ME.txt", kind: "file" },
  ]);
}

function level1Nodes(): FileNode[] {
  return withDesktop([
    { id: "fld-pics", name: "Pictures", kind: "folder" },
    { id: "fld-school", name: "School", kind: "folder" },
    { id: "file-cat", name: "cat.png", kind: "file" },
    { id: "file-hw", name: "homework.txt", kind: "file" },
  ]);
}

function level2Nodes(): FileNode[] {
  const nodes = baseNodes();
  nodes.push(
    { id: "fld-photos", name: "Photos", parentId: DESKTOP_ID, kind: "folder" },
    { id: "fld-work", name: "Work", parentId: DESKTOP_ID, kind: "folder" },
    {
      id: "fld-installers",
      name: "Installers",
      kind: "folder",
      parentId: DESKTOP_ID,
    },
    {
      id: "fld-downloads",
      name: "Downloads",
      kind: "folder",
      parentId: DESKTOP_ID,
    },
    {
      id: "f-beach",
      name: "beach.jpg",
      kind: "file",
      parentId: "fld-downloads",
    },
    {
      id: "f-budget",
      name: "budget.xlsx",
      kind: "file",
      parentId: "fld-downloads",
    },
    {
      id: "f-game",
      name: "game-installer.msi",
      kind: "file",
      parentId: "fld-downloads",
    },
  );
  return nodes;
}

export function buildInitialFs(levelIndex: number): FsSlice {
  switch (levelIndex) {
    case 0:
      return initialFsSlice(level0Nodes());
    case 1:
      return initialFsSlice(level1Nodes());
    case 2:
      return initialFsSlice(level2Nodes());
    case 3:
      return initialFsSlice(
        withDesktop([{ id: "fld-docs", name: "Documents", kind: "folder" }]),
      );
    default:
      return initialFsSlice(level0Nodes());
  }
}

export function freshSave(levelIndex: number): SaveV1 {
  return {
    version: 1,
    levelIndex,
    subIndex: 0,
    fs: buildInitialFs(Math.min(levelIndex, LAST_PLAYABLE)),
    quizChoiceId: null,
  };
}

function parentOf(fs: FsSlice, fileId: string) {
  return fs.nodes.find((n) => n.id === fileId)?.parentId;
}

/** How many sub-challenges this main level has (quiz = 1). */
export function subCount(levelIndex: number): number {
  switch (levelIndex) {
    case 0:
      return 2;
    case 1:
      return 2;
    case 2:
      return 3;
    case 3:
      return 1;
    default:
      return 1;
  }
}

/**
 * Align subIndex with filesystem progress (fixes older saves without `subIndex`).
 */
export function migrateSubIndex(
  levelIndex: number,
  fs: FsSlice,
  _storedSub: number | undefined,
): number {
  const n = subCount(levelIndex);
  for (let i = 0; i < n; i++) {
    if (!isSubComplete(levelIndex, i, fs)) return i;
  }
  return Math.max(0, n - 1);
}

export function isSubComplete(
  levelIndex: number,
  subIndex: number,
  fs: FsSlice,
): boolean {
  switch (levelIndex) {
    case 0:
      if (subIndex === 0) return fs.visitedFolderIds.includes("fld-games");
      if (subIndex === 1) return fs.visitedFolderIds.includes("fld-docs");
      return false;
    case 1:
      if (subIndex === 0) return parentOf(fs, "file-cat") === "fld-pics";
      if (subIndex === 1) return parentOf(fs, "file-hw") === "fld-school";
      return false;
    case 2:
      if (subIndex === 0) return parentOf(fs, "f-beach") === "fld-photos";
      if (subIndex === 1) return parentOf(fs, "f-budget") === "fld-work";
      if (subIndex === 2) return parentOf(fs, "f-game") === "fld-installers";
      return false;
    default:
      return false;
  }
}

export function isFsLevelComplete(levelIndex: number, fs: FsSlice): boolean {
  const n = subCount(levelIndex);
  for (let i = 0; i < n; i++) {
    if (!isSubComplete(levelIndex, i, fs)) return false;
  }
  return true;
}

export const QUIZ_CORRECT_ID = "opt-docs";

export function isQuizComplete(choiceId: string | null) {
  return choiceId === QUIZ_CORRECT_ID;
}

export function levelTitle(levelIndex: number): string {
  switch (levelIndex) {
    case 0:
      return "Find Documents";
    case 1:
      return "Put files away";
    case 2:
      return "Rescue Downloads";
    case 3:
      return "Safe saving";
    default:
      return "Complete";
  }
}

/** Short context for the whole level. */
export function levelBlurb(levelIndex: number): string {
  switch (levelIndex) {
    case 0:
      return "Folders are like drawers—open them with a click. Use Back to return to the folder above.";
    case 1:
      return "Drag a file onto a folder to move it—or tap a file, then tap a folder below.";
    case 2:
      return "Drag one file at a time onto the right folder (or use tap + folder buttons).";
    case 3:
      return "Where should you save homework so you can find it later?";
    default:
      return "";
  }
}

/** Current sub-challenge instruction. */
export function subBlurb(levelIndex: number, subIndex: number): string {
  switch (levelIndex) {
    case 0:
      if (subIndex === 0)
        return "First: click the Games folder to open it. Then use Back to return to the Desktop.";
      return "Next: open the Documents folder the same way.";
    case 1:
      if (subIndex === 0)
        return "Drag cat.png onto the Pictures folder (or select it, then pick Pictures).";
      return "Drag homework.txt onto the School folder.";
    case 2:
      if (subIndex === 0) return "Drag beach.jpg onto Photos.";
      if (subIndex === 1) return "Drag budget.xlsx onto Work.";
      return "Drag game-installer.msi onto Installers.";
    case 3:
      return levelBlurb(3);
    default:
      return "";
  }
}