export const APP_DIAGNOSTIC_SCHEMA_VERSION = 1 as const;
export const MAX_APP_DIAGNOSTIC_ENTRIES = 200;

export const APP_DIAGNOSTIC_MESSAGES = {
  VIEWPORT_INIT_FAILED: "Viewport: unavailable",
  ACTION_CONFLICT: "Action: another project operation is running",
  ACTION_LOCK_FAILED: "Action: retry required",
  RECENT_PROJECT_LIST_FAILED: "Storage: recent projects unavailable",
  RECENT_PROJECT_REPAIR_FAILED: "Storage: recent project repair failed",
  RECENT_PROJECT_UPDATE_FAILED: "Storage: recent project update failed",
  STORAGE_BUDGET_FAILED: "Storage: budget unavailable",
  STORAGE_CLEANUP_FAILED: "Storage: cleanup failed",
  OPERATION_LOG_FAILED: "Storage: operation log unavailable",
  COMMAND_FAILED: "Engine: command failed",
  IMAGE_IMPORT_FAILED: "Image import failed",
  GREASE_PENCIL_EDIT_FAILED: "Grease Pencil edit failed",
  CURVE_EDIT_FAILED: "Curve edit failed",
  LOD_CACHE_READ_FAILED: "Storage: LOD cache unavailable; generated geometry retained",
  LOD_GENERATION_FAILED: "Engine: LOD generation failed",
  ENGINE_WORKER_TERMINATED: "Engine: Worker stopped; project remains available",
  ENGINE_START_FAILED: "Engine: unavailable",
  MANIFEST_REJECTED: "Manifest: rejected",
  STORAGE_WORKER_TERMINATED: "Storage: Worker stopped; project remains available",
  STORAGE_START_FAILED: "Storage: unavailable",
  PBR_ASSET_INVALID: "PBR asset unavailable",
  BLEND_OPEN_FAILED: "Engine: .blend open failed",
  POST_COMMIT_MAINTENANCE_FAILED: "Storage: post-commit maintenance failed",
  PROJECT_RECOVERY_FAILED: "Recovery: project could not be restored",
  WORKER_RECOVERY_FAILED: "Recovery: Worker restart failed",
  BLEND_SAVE_FAILED: "Engine: .blend save failed",
  BLEND_DOWNLOAD_FAILED: "Engine: .blend download failed",
  GLB_PROJECT_UNAVAILABLE: "GLB: no open project",
  GLB_EXPORT_BLOCKED: "GLB: export blocked",
  GLB_EXPORT_FAILED: "GLB: export failed",
  AUTOSAVE_FAILED: "Engine: autosave failed",
} as const;

export type AppDiagnosticCode = keyof typeof APP_DIAGNOSTIC_MESSAGES;
export type AppDiagnosticArea = "ACTION" | "ENGINE" | "STORAGE" | "VIEWPORT" | "EXPORT" | "RUNTIME";
export type AppDiagnosticContextValue = string | number | boolean | null;

export interface AppDiagnosticEntry {
  schemaVersion: typeof APP_DIAGNOSTIC_SCHEMA_VERSION;
  sequence: number;
  occurredAt: string;
  area: AppDiagnosticArea;
  code: AppDiagnosticCode;
  summary: string;
  detail: string;
  sourceCode?: string;
  stack?: string;
  cause?: string;
  context?: Record<string, AppDiagnosticContextValue>;
}

export interface AppDiagnosticReport {
  schemaVersion: typeof APP_DIAGNOSTIC_SCHEMA_VERSION;
  product: "Web Blender Modeler V1";
  generatedAt: string;
  runtime: {
    url: string;
    userAgent: string;
    language: string;
    crossOriginIsolated: boolean;
  };
  project: {
    projectId: string;
    revision: number;
  };
  entries: AppDiagnosticEntry[];
}

function objectString(value: unknown): string | undefined {
  if (typeof value !== "object" || value === null) return undefined;
  try {
    const seen = new WeakSet<object>();
    return JSON.stringify(value, (_key, candidate: unknown) => {
      if (candidate instanceof Error) {
        return { name: candidate.name, message: candidate.message, stack: candidate.stack, cause: candidate.cause };
      }
      if (typeof candidate === "object" && candidate !== null) {
        if (seen.has(candidate)) return "[Circular]";
        seen.add(candidate);
      }
      return candidate;
    });
  }
  catch {
    return "[Unserializable diagnostic detail]";
  }
}

function propertyString(value: unknown, property: string): string | undefined {
  if (typeof value !== "object" || value === null || !(property in value)) return undefined;
  const candidate = (value as Record<string, unknown>)[property];
  return typeof candidate === "string" && candidate ? candidate : undefined;
}

function diagnosticDetail(error: unknown): Pick<AppDiagnosticEntry, "detail" | "sourceCode" | "stack" | "cause"> {
  if (error instanceof Error) {
    return {
      detail: error.message || error.name,
      sourceCode: propertyString(error, "code"),
      stack: error.stack,
      cause: error.cause instanceof Error ? error.cause.message : typeof error.cause === "string" ? error.cause : objectString(error.cause),
    };
  }
  if (typeof error === "string") return { detail: error };
  const message = propertyString(error, "message");
  const extraDetail = propertyString(error, "detail");
  return {
    detail: [message, extraDetail].filter(Boolean).join("; ") || objectString(error) || String(error),
    sourceCode: propertyString(error, "code"),
    stack: propertyString(error, "stack"),
    cause: propertyString(error, "cause"),
  };
}

export function createAppDiagnosticEntry(input: {
  sequence: number;
  occurredAt: string;
  area: AppDiagnosticArea;
  code: AppDiagnosticCode;
  error: unknown;
  context?: Record<string, AppDiagnosticContextValue>;
}): AppDiagnosticEntry {
  if (!Number.isSafeInteger(input.sequence) || input.sequence <= 0) throw new Error("APP_DIAGNOSTIC_SEQUENCE_INVALID");
  if (!Number.isFinite(Date.parse(input.occurredAt)) || new Date(input.occurredAt).toISOString() !== input.occurredAt) throw new Error("APP_DIAGNOSTIC_TIMESTAMP_INVALID");
  const detail = diagnosticDetail(input.error);
  return {
    schemaVersion: APP_DIAGNOSTIC_SCHEMA_VERSION,
    sequence: input.sequence,
    occurredAt: input.occurredAt,
    area: input.area,
    code: input.code,
    summary: APP_DIAGNOSTIC_MESSAGES[input.code],
    detail: detail.detail,
    ...(detail.sourceCode ? { sourceCode: detail.sourceCode } : {}),
    ...(detail.stack ? { stack: detail.stack } : {}),
    ...(detail.cause ? { cause: detail.cause } : {}),
    ...(input.context ? { context: { ...input.context } } : {}),
  };
}

export function appendAppDiagnostic(entries: readonly AppDiagnosticEntry[], entry: AppDiagnosticEntry, limit = MAX_APP_DIAGNOSTIC_ENTRIES): AppDiagnosticEntry[] {
  if (!Number.isSafeInteger(limit) || limit <= 0) throw new Error("APP_DIAGNOSTIC_LIMIT_INVALID");
  return [...entries, entry].slice(-limit);
}

export function createAppDiagnosticReport(input: Omit<AppDiagnosticReport, "schemaVersion" | "product" | "entries"> & { entries: readonly AppDiagnosticEntry[] }): AppDiagnosticReport {
  if (!Number.isFinite(Date.parse(input.generatedAt)) || new Date(input.generatedAt).toISOString() !== input.generatedAt) throw new Error("APP_DIAGNOSTIC_REPORT_TIMESTAMP_INVALID");
  return {
    schemaVersion: APP_DIAGNOSTIC_SCHEMA_VERSION,
    product: "Web Blender Modeler V1",
    generatedAt: input.generatedAt,
    runtime: { ...input.runtime },
    project: { ...input.project },
    entries: [...input.entries].sort((left, right) => left.sequence - right.sequence),
  };
}