/**
 * Collect packages from a games root directory.
 *
 * A games root contains yaml/json/toml files and markdown files with
 * definition code blocks. The loader:
 *
 * 1. Reads real files and extracts virtual files from markdown code blocks
 *    (virtual wins over real files with the same name).
 * 2. Parses each def file into JSON objects.
 * 3. Recognizes `role: package` objects, expands their `$variants`, follows
 *    their `include` patterns, and assembles the package's parts, surfaces,
 *    and setups.
 *
 * See docs/bgm-format.md for the format's concrete behavior.
 */
import * as path from 'node:path';
import picomatch from 'picomatch';
import { collectVirtualFiles } from './markdown.js';
import { parseDefText, readDefFiles } from './parse.js';
import { validatePackage, validatePart, validateSetup, validateSurface } from './schemas.js';
import { expandVariants } from './variants.js';
import {
  BgmError,
  type DefFile,
  type ParsedDef,
  type Package,
  type PackageDef,
  type Part,
  type Role,
  type Setup,
  type Surface,
} from './types.js';

const ROLES = new Set<Role>(['package', 'part', 'surface', 'setup']);

/** Every definition parsed from a def file, keyed by its path-style name. */
export interface DefMap {
  /** All def files (real + virtual), keyed by name. */
  files: Map<string, DefFile[]>;
  /** All parsed definitions, keyed by file name. */
  defs: Map<string, ParsedDef[]>;
}

/**
 * Load a games root into a def map.
 *
 * @param root the path-style name of the root, e.g. `harbor`
 * @param rootDir the absolute path of the games root
 */
export function loadDefs(root: string, rootDir: string): DefMap {
  const realFiles = readDefFiles(rootDir, root);
  const markdownFiles = new Map<string, string>();
  const others: DefFile[] = [];

  for (const file of realFiles) {
    if (file.kind === 'markdown') markdownFiles.set(file.name, file.text);
    else others.push(file);
  }

  const virtualFiles = collectVirtualFiles(markdownFiles);
  const files = new Map<string, DefFile[]>();
  // Real files first, virtual files override (virtual wins per the format).
  for (const file of others) files.set(file.name, [file]);
  for (const [name, list] of virtualFiles) files.set(name, list);

  const defs = new Map<string, ParsedDef[]>();
  for (const [name, list] of files) {
    const parsed: ParsedDef[] = [];
    for (const file of list) parsed.push(...parseDefText(file));
    defs.set(name, parsed);
  }

  return { files, defs };
}

/**
 * Collect all packages from the given def map.
 *
 * @param rootDir the absolute path of the games root; `$variants` file paths
 *   resolve relative to their def file's directory within the root
 */
export function collectPackages(defMap: DefMap, rootDir: string): Package[] {
  const packages = new Map<string, PackageAcc>();
  const byRole = new Map<string, ParsedDef[]>();

  // Group parsed defs by role.
  for (const [file, defs] of defMap.defs) {
    const list: ParsedDef[] = [];
    for (const def of defs) {
      const role = def.value['role'];
      if (role !== undefined && typeof role === 'string' && ROLES.has(role as Role)) {
        list.push(def);
        byRole.set(file, list);
      }
    }
  }

  const accs: PackageAcc[] = [];
  for (const [file, defs] of byRole) {
    for (const def of defs) {
      const role = def.value['role'] as Role;
      if (role === 'package') {
        const pkg = asPackage(def, file);
        const baseDir = path.posix.dirname(file).replace(/^\/+/, '');
        accs.push(new PackageAcc(pkg, defMap, rootDir, baseDir));
      }
    }
  }

  const result: Package[] = [];
  for (const acc of accs) {
    acc.collect();
    result.push(acc.toPackage());
  }
  return result;
}

/** Identity validation: `type#id` must be unique within a package. */
class PackageAcc {
  readonly parts = new Map<string, Part>();
  readonly surfaces = new Map<string, Surface>();
  readonly setups = new Map<string, Setup>();
  readonly byRole = new Map<string, string[]>();

  constructor(
    readonly pkg: PackageDef,
    private readonly defs: DefMap,
    private readonly rootDir: string,
    /** Path-style directory of the package declaration, e.g. `carcassonne`. */
    private readonly baseDir: string,
  ) {}

  collect() {
    const include = this.pkg.include ?? ['./**/*.yaml'];
    const names = this.expandIncludes(include);
    for (const name of names) {
      const fileDefs = this.defs.defs.get(name);
      if (!fileDefs) continue;
      for (const def of fileDefs) {
        const role = def.value['role'];
        if (typeof role !== 'string' || !ROLES.has(role as Role) || role === 'package') continue;
        this.add(role as Role, def, name);
      }
    }
  }

  /** Expand `$variants` on a def object into a list of concrete objects. */
  private expand(obj: Record<string, unknown>, baseName: string, source: string): Record<string, unknown>[] {
    if (!('$variants' in obj)) return [obj];
    const rows = expandVariants(obj['$variants'], baseName, this.defs.files, source);
    const { $variants: _v, ...base } = obj;
    return rows.map((row) => ({ ...base, ...row }));
  }

  private expandIncludes(patterns: string[]): string[] {
    // Match include patterns against the parsed definitions' names, which
    // cover both real files and markdown code blocks. Patterns are relative
    // to the package declaration's own directory (e.g. `./**/*.yaml` means
    // this package's folder and below), so a package never absorbs defs from
    // a sibling game. A leading `/` marks a pattern as root-relative.
    // Def names carry a leading `/` (from the empty games root), so resolved
    // patterns are prefixed to match.
    const names = new Set<string>();
    for (const pattern of patterns) {
      const resolved = pattern.startsWith('/')
        ? pattern
        : `/${path.posix.join(this.baseDir, pattern)}`;
      const matcher = picomatch(resolved, { dot: true });
      for (const name of this.defs.defs.keys()) {
        if (matcher(name)) names.add(name);
      }
    }
    return [...names];
  }

  private add(role: Role, def: ParsedDef, fileName: string) {
    const expanded = this.expand(def.value, def.file, def.source);
    for (const obj of expanded) {
      switch (role) {
        case 'part': {
          const part = asPart(obj, fileName);
          const key = `${part.type}#${part.id}`;
          if (this.parts.has(key)) {
            throw new BgmError(`Duplicate part "${key}"`, fileName);
          }
          this.parts.set(key, part);
          break;
        }
        case 'surface': {
          const surface = asSurface(obj, fileName, this.defs.files);
          const key = `${surface.type}#${surface.id}`;
          if (this.surfaces.has(key)) {
            throw new BgmError(`Duplicate surface "${key}"`, fileName);
          }
          this.surfaces.set(key, surface);
          break;
        }
        case 'setup': {
          const setup = asSetup(obj, fileName);
          const key = `${setup.type}#${setup.id}`;
          if (this.setups.has(key)) {
            throw new BgmError(`Duplicate setup "${key}"`, fileName);
          }
          this.setups.set(key, setup);
          break;
        }
      }
    }
  }

  toPackage(): Package {
    return { meta: metaOf(this.pkg), parts: this.parts, surfaces: this.surfaces, setups: this.setups };
  }
}

function metaOf(pkg: PackageDef) {
  const { role: _role, include: _include, ...meta } = pkg;
  return meta;
}

function asPackage(def: ParsedDef, source: string): PackageDef {
  const obj = def.value;
  try {
    return validatePackage(obj) as unknown as PackageDef;
  } catch (err) {
    throw wrapZod(err, source);
  }
}

function asPart(obj: Record<string, unknown>, source: string): Part {
  try {
    const part = validatePart(obj) as unknown as Part;
    // Resolve relative asset paths against the directory of the source file
    // (path-style name relative to the games root, e.g. `harbor/parts/`).
    // Real files may carry a leading slash from an empty root; strip it.
    const dir = path.posix.dirname(source).replace(/^\/+/, '');
    part.baseUrl = dir ? `${dir}/` : '';
    return part;
  } catch (err) {
    throw wrapZod(err, source);
  }
}

function asSurface(
  obj: Record<string, unknown>,
  source: string,
  defs: Map<string, DefFile[]>,
): Surface {
  const value: Record<string, unknown> = { ...obj };
  delete value['role'];

  // Expand `candidates.$variants` on each route into a concrete array.
  if (Array.isArray(value['layout'])) {
    value['layout'] = value['layout'].map((route) => {
      if (typeof route !== 'object' || route === null) return route;
      const r = route as Record<string, unknown>;
      const cand = r['candidates'];
      if (cand && typeof cand === 'object' && !Array.isArray(cand) && '$variants' in cand) {
        const rows = expandVariants(cand['$variants'], source, defs, source);
        const { $variants: _v, ...base } = cand as Record<string, unknown>;
        return { ...r, candidates: rows.map((row) => ({ ...base, ...row })) };
      }
      return route;
    });
  }
  try {
    return validateSurface(value) as unknown as Surface;
  } catch (err) {
    throw wrapZod(err, source);
  }
}

function asSetup(obj: Record<string, unknown>, source: string): Setup {
  const value: Record<string, unknown> = { ...obj };
  delete value['role'];
  try {
    return validateSetup(value) as unknown as Setup;
  } catch (err) {
    throw wrapZod(err, source);
  }
}

/** Wrap a zod error with the source location. */
function wrapZod(err: unknown, source: string): BgmError {
  const message = err instanceof Error ? err.message : String(err);
  return new BgmError(`Invalid definition: ${message}`, source);
}