import { AnthropicError } from '../core/error';

// Standard Schema spec types, copied from `@standard-schema/spec@1.1.0` (MIT) as the spec
// recommends. See https://standardschema.dev

/** The Standard Typed interface. This is a base type extended by other specs. */
export interface StandardTypedV1<Input = unknown, Output = Input> {
  /** The Standard properties. */
  readonly '~standard': StandardTypedV1.Props<Input, Output>;
}

export declare namespace StandardTypedV1 {
  /** The Standard Typed properties interface. */
  interface Props<Input = unknown, Output = Input> {
    /** The version number of the standard. */
    readonly version: 1;
    /** The vendor name of the schema library. */
    readonly vendor: string;
    /** Inferred types associated with the schema. */
    readonly types?: Types<Input, Output> | undefined;
  }

  /** The Standard Typed types interface. */
  interface Types<Input = unknown, Output = Input> {
    /** The input type of the schema. */
    readonly input: Input;
    /** The output type of the schema. */
    readonly output: Output;
  }

  /** Infers the input type of a Standard Typed. */
  type InferInput<Schema extends StandardTypedV1> = NonNullable<Schema['~standard']['types']>['input'];

  /** Infers the output type of a Standard Typed. */
  type InferOutput<Schema extends StandardTypedV1> = NonNullable<Schema['~standard']['types']>['output'];
}

/** The Standard Schema interface. */
export interface StandardSchemaV1<Input = unknown, Output = Input> {
  /** The Standard Schema properties. */
  readonly '~standard': StandardSchemaV1.Props<Input, Output>;
}

export declare namespace StandardSchemaV1 {
  /** The Standard Schema properties interface. */
  interface Props<Input = unknown, Output = Input> extends StandardTypedV1.Props<Input, Output> {
    /** Validates unknown input values. */
    readonly validate: (
      value: unknown,
      options?: StandardSchemaV1.Options | undefined,
    ) => Result<Output> | Promise<Result<Output>>;
  }

  /** The result interface of the validate function. */
  type Result<Output> = SuccessResult<Output> | FailureResult;

  /** The result interface if validation succeeds. */
  interface SuccessResult<Output> {
    /** The typed output value. */
    readonly value: Output;
    /** A falsy value for `issues` indicates success. */
    readonly issues?: undefined;
  }

  interface Options {
    /** Explicit support for additional vendor-specific parameters, if needed. */
    readonly libraryOptions?: Record<string, unknown> | undefined;
  }

  /** The result interface if validation fails. */
  interface FailureResult {
    /** The issues of failed validation. */
    readonly issues: ReadonlyArray<Issue>;
  }

  /** The issue interface of the failure output. */
  interface Issue {
    /** The error message of the issue. */
    readonly message: string;
    /** The path of the issue, if any. */
    readonly path?: ReadonlyArray<PropertyKey | PathSegment> | undefined;
  }

  /** The path segment interface of the issue. */
  interface PathSegment {
    /** The key representing a path segment. */
    readonly key: PropertyKey;
  }

  /** The Standard types interface. */
  interface Types<Input = unknown, Output = Input> extends StandardTypedV1.Types<Input, Output> {}

  /** Infers the input type of a Standard. */
  type InferInput<Schema extends StandardTypedV1> = StandardTypedV1.InferInput<Schema>;

  /** Infers the output type of a Standard. */
  type InferOutput<Schema extends StandardTypedV1> = StandardTypedV1.InferOutput<Schema>;
}

/** The Standard JSON Schema interface. */
export interface StandardJSONSchemaV1<Input = unknown, Output = Input> {
  /** The Standard JSON Schema properties. */
  readonly '~standard': StandardJSONSchemaV1.Props<Input, Output>;
}

export declare namespace StandardJSONSchemaV1 {
  /** The Standard JSON Schema properties interface. */
  interface Props<Input = unknown, Output = Input> extends StandardTypedV1.Props<Input, Output> {
    /** Methods for generating the input/output JSON Schema. */
    readonly jsonSchema: StandardJSONSchemaV1.Converter;
  }

  /** The Standard JSON Schema converter interface. */
  interface Converter {
    /** Converts the input type to JSON Schema. May throw if conversion is not supported. */
    readonly input: (options: StandardJSONSchemaV1.Options) => Record<string, unknown>;
    /** Converts the output type to JSON Schema. May throw if conversion is not supported. */
    readonly output: (options: StandardJSONSchemaV1.Options) => Record<string, unknown>;
  }

  /**
   * The target version of the generated JSON Schema.
   *
   * It is *strongly recommended* that implementers support `"draft-2020-12"` and `"draft-07"`, as they
   * are both in wide use. All other targets can be implemented on a best-effort basis. Libraries should
   * throw if they don't support a specified target.
   *
   * The `"openapi-3.0"` target is intended as a standardized specifier for OpenAPI 3.0 which is a
   * superset of JSON Schema `"draft-04"`.
   */
  type Target = 'draft-2020-12' | 'draft-07' | 'openapi-3.0' | ({} & string);

  /** The options for the input/output methods. */
  interface Options {
    /** Specifies the target version of the generated JSON Schema. Support for all versions is on a best-effort basis. If a given version is not supported, the library should throw. */
    readonly target: Target;
    /** Explicit support for additional vendor-specific parameters, if needed. */
    readonly libraryOptions?: Record<string, unknown> | undefined;
  }

  /** The Standard types interface. */
  interface Types<Input = unknown, Output = Input> extends StandardTypedV1.Types<Input, Output> {}

  /** Infers the input type of a Standard. */
  type InferInput<Schema extends StandardTypedV1> = StandardTypedV1.InferInput<Schema>;

  /** Infers the output type of a Standard. */
  type InferOutput<Schema extends StandardTypedV1> = StandardTypedV1.InferOutput<Schema>;
}

/**
 * Returns `jsonSchema` if given, otherwise the schema's Standard JSON Schema `input`
 * representation (the model produces the value that the validator consumes).
 */
export function standardSchemaToJSONSchema(
  schema: StandardSchemaV1,
  jsonSchema?: Record<string, unknown> | undefined,
): Record<string, unknown> {
  if (jsonSchema) {
    return jsonSchema;
  }

  const std: StandardSchemaV1.Props & Partial<StandardJSONSchemaV1.Props> = schema['~standard'];
  if (std.jsonSchema) {
    return std.jsonSchema.input({ target: 'draft-2020-12' });
  }

  throw new AnthropicError(
    `Could not derive a JSON Schema from this ${std.vendor} schema as it does not implement Standard JSON Schema (\`~standard.jsonSchema\`). Pass the \`jsonSchema\` option, or use a library version that implements it (e.g. zod >= 4.2, or valibot via \`toStandardJsonSchema()\`).`,
  );
}

/**
 * Validates `value` with `~standard.validate` and returns the typed output, throwing an
 * `AnthropicError` on issues. Validation must be synchronous because `parse` hooks are.
 */
export function parseWithStandardSchema<Schema extends StandardSchemaV1>(
  schema: Schema,
  value: unknown,
): StandardSchemaV1.InferOutput<Schema> {
  const result = schema['~standard'].validate(value);

  if (result instanceof Promise) {
    // avoid an unhandled rejection from the discarded result
    result.catch(() => {});
    throw new AnthropicError(
      `Async validation is not supported: the ${schema['~standard'].vendor} schema's \`~standard.validate()\` returned a Promise.`,
    );
  }

  if (result.issues) {
    const formattedIssues = result.issues.slice(0, 5).map(formatIssue).join('\n');
    const issueCount = result.issues.length;
    const suffix = issueCount > 5 ? `\n  ... and ${issueCount - 5} more issue(s)` : '';

    throw new AnthropicError(
      `Schema validation failed with ${issueCount} issue(s):\n${formattedIssues}${suffix}`,
    );
  }

  return result.value;
}

function formatIssue(issue: StandardSchemaV1.Issue): string {
  const path = (issue.path ?? [])
    .map((segment) => String(typeof segment === 'object' ? segment.key : segment))
    .join('.');
  return path ? `  - ${path}: ${issue.message}` : `  - ${issue.message}`;
}