/** Shared contract for the Pascal compiler service (tutorial section 27).
 *
 *  The frontend never spawns the compiler directly: it calls this service
 *  over RPC and the backend runs `fpc` asynchronously.
 *  Other compilers can implement the same interface without changing the rest of the IDE.
 */

export const PascalCompilerServicePath = '/services/pascal-compiler';
export const PascalCompiler = Symbol('PascalCompiler');

export type BuildSeverity = 'error' | 'warning' | 'info';

export interface BuildDiagnostic {
  /** File path as reported by the compiler (relative to the project root). */
  file: string;
  /** Zero-based line and character. */
  line: number;
  character: number;
  message: string;
  severity: BuildSeverity;
}

export interface BuildResult {
  success: boolean;
  exitCode: number;
  /** Exact command line that was executed (for transparency). */
  command: string;
  /** Combined stdout/stderr of the compiler. */
  output: string;
  diagnostics: BuildDiagnostic[];
  /** Project source statistics and output size (present on success). */
  stats?: BuildStats;
}

/** Source census for the build report dialog. */
export interface BuildStats {
  /** Number of `.pas`/`.pp` files under the project root. */
  files: number;
  /** Total lines across those files. */
  lines: number;
  /** Built executable size in bytes (-1 when unavailable). */
  outputSize: number;
}

/** Human-readable byte count (`45.2 KB`, `3.1 MB`). Pure and testable. */
export function formatBytes(bytes: number): string {
  if (!Number.isFinite(bytes) || bytes < 0) return '—';
  if (bytes < 1024) return `${bytes} B`;
  const kb = bytes / 1024;
  if (kb < 1024) return `${kb.toFixed(1)} KB`;
  return `${(kb / 1024).toFixed(1)} MB`;
}

export type CompilerType = 'fpc' | 'blaise';

export interface CompilerOptions {
  /** Compiler backend: "fpc" (default) or the Blaise compiler. */
  type?: CompilerType;
  /** Compiler executable, e.g. "fpc" or an absolute path. */
  path: string;
  options: string[];
}

export interface PascalProject {
  name: string;
  /** Absolute workspace folder containing pascal.json. */
  root: string;
  /** Main file, relative to root (e.g. "src/Main.pas"). */
  main: string;
  /** Built executable, relative to root. Defaults to bin/<name>. */
  output?: string;
  compiler: CompilerOptions;
  /** True when pascal.json sets an explicit compiler path. */
  compilerPathExplicit: boolean;
}

export interface CompilerInfo {
  path: string;
  /** First line of `fpc --version`. */
  version: string;
}

export interface PascalCompiler {
  /** Probe a compiler executable; undefined when it cannot be run. */
  detect(compilerPath?: string): Promise<CompilerInfo | undefined>;
  /** Compile (and link) the project main file. */
  build(project: PascalProject): Promise<BuildResult>;
  /** Remove build outputs (best-effort). */
  clean(project: PascalProject): Promise<void>;
  /** Build, then execute the produced program and capture its output. */
  run(project: PascalProject): Promise<BuildResult>;
}

/** Minimal `pascal.json` reader (tutorial sections 23/33). Pure and testable. */
export function parseProjectFile(root: string, jsonText: string): PascalProject {
  const raw = JSON.parse(jsonText) as {
    name?: unknown; main?: unknown; output?: unknown;
    compiler?: { type?: unknown; path?: unknown; options?: unknown };
  };
  if (typeof raw.name !== 'string' || raw.name.length === 0) {
    throw new Error('pascal.json: missing "name".');
  }
  if (typeof raw.main !== 'string' || raw.main.length === 0) {
    throw new Error('pascal.json: missing "main".');
  }
  const compiler = raw.compiler ?? {};
  const type = compiler.type === 'blaise' ? 'blaise' as const : 'fpc' as const;
  const options = Array.isArray(compiler.options)
    ? compiler.options.filter((o): o is string => typeof o === 'string')
    : [];
  const explicitPath = typeof compiler.path === 'string' && compiler.path.length > 0;
  return {
    name: raw.name,
    root,
    main: raw.main,
    output: typeof raw.output === 'string' ? raw.output : undefined,
    compiler: {
      type,
      path: explicitPath ? (compiler.path as string) : (type === 'blaise' ? 'blaise' : 'fpc'),
      options,
    },
    compilerPathExplicit: explicitPath,
  };
}

/** Default executable path for a project (bin/<name> under root). */
export function defaultOutput(project: PascalProject): string {
  return project.output ?? `bin/${project.name}`;
}

export interface ProvidedTask {
  label: string;
  group?: { kind: 'build' | 'rebuild'; isDefault?: boolean } | 'clean';
  command: string;
  args: string[];
  dependsOn?: string;
}

/** Pure task list for a project (tested headlessly; the Theia provider wraps these). */
export function buildProvidedTasks(project: PascalProject): ProvidedTask[] {
  const out = defaultOutput(project);
  const buildArgs = project.compiler.type === 'blaise'
    ? ['--source', project.main, '--output', out, ...project.compiler.options]
    : ['-g', ...project.compiler.options, '-o' + out, project.main];
  return [
    { label: 'Pascal: Build', group: { kind: 'build', isDefault: true }, command: project.compiler.path, args: buildArgs },
    { label: 'Pascal: Clean', group: 'clean', command: 'rm', args: ['-f', out] },
    { label: 'Pascal: Rebuild', group: { kind: 'rebuild' }, command: project.compiler.path, args: buildArgs },
    { label: 'Pascal: Run', command: `./${out}`, args: [], dependsOn: 'Pascal: Build' },
  ];
}