import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest';
import { importModule } from '../../src/esm';
import logger from '../../src/logger';
import { runPython } from '../../src/python/pythonUtils';
import {
  FILE_TRANSFORM_LABEL,
  getTransformErrorMessage,
  getTransformLabel,
  INLINE_FUNCTION_LABEL,
  INLINE_STRING_LABEL,
  TransformInputType,
  transform,
} from '../../src/util/transform';

import type { TransformFunction } from '../../src/types/transform';

vi.mock('../../src/esm', () => ({
  importModule: vi.fn(),
  getDirectory: vi.fn().mockReturnValue('/test/dir'),
}));

vi.mock('../../src/logger', () => ({
  default: {
    error: vi.fn(),
    warn: vi.fn(),
    info: vi.fn(),
    debug: vi.fn(),
  },
}));

vi.mock('../../src/python/pythonUtils', () => ({
  runPython: vi.fn().mockImplementation(async (_filePath, _functionName, args) => {
    const [output] = args;
    return output.toUpperCase() + ' FROM PYTHON';
  }),
}));

vi.mock('fs', () => ({
  unlink: vi.fn(),
}));

vi.mock('glob', () => ({
  globSync: vi.fn(),
}));

vi.mock('../../src/database', () => ({
  getDb: vi.fn(),
}));

const mockedImportModule = vi.mocked(importModule);

describe('util', () => {
  beforeEach(() => {
    vi.clearAllMocks();
  });

  describe('transform', () => {
    afterEach(() => {
      vi.clearAllMocks();
      vi.resetModules();
    });

    it('transforms output using a direct function', async () => {
      const output = 'original output';
      const context = { vars: { key: 'value' }, prompt: { id: '123' } };
      const transformFunction = 'output.toUpperCase()';
      const transformedOutput = await transform(transformFunction, output, context);
      expect(transformedOutput).toBe('ORIGINAL OUTPUT');
    });

    it('transforms vars using a direct function', async () => {
      const vars = { key: 'value' };
      const context = { vars: {}, prompt: { id: '123' } };
      const transformFunction = 'JSON.stringify(vars)';
      const transformedOutput = await transform(
        transformFunction,
        vars,
        context,
        true,
        TransformInputType.VARS,
      );
      expect(transformedOutput).toBe('{"key":"value"}');
    });

    it('transforms output using an imported function from a file', async () => {
      const output = 'hello';
      const context = { vars: { key: 'value' }, prompt: { id: '123' } };
      mockedImportModule.mockResolvedValueOnce((output: string) => output.toUpperCase());

      const transformFunctionPath = 'file://transform.js';
      const transformedOutput = await transform(transformFunctionPath, output, context);
      expect(transformedOutput).toBe('HELLO');
    });

    it('transforms vars using a direct function from a file', async () => {
      const vars = { key: 'value' };
      const context = { vars: {}, prompt: {} };
      mockedImportModule.mockResolvedValueOnce((vars: any) => ({
        ...vars,
        key: 'transformed',
      }));
      const transformFunctionPath = 'file://transform.js';
      const transformedOutput = await transform(
        transformFunctionPath,
        vars,
        context,
        true,
        TransformInputType.VARS,
      );
      expect(transformedOutput).toEqual({ key: 'transformed' });
    });

    it('throws error if transform function does not return a value', async () => {
      const output = 'test';
      const context = { vars: {}, prompt: {} };
      const transformFunction = ''; // Empty function, returns undefined
      await expect(transform(transformFunction, output, context)).rejects.toThrow(
        'Transform function did not return a value',
      );
    });

    it('throws error if file does not export a function', async () => {
      const output = 'test';
      const context = { vars: {}, prompt: {} };
      mockedImportModule.mockResolvedValueOnce('banana');
      const transformFunctionPath = 'file://transform.js';
      await expect(transform(transformFunctionPath, output, context)).rejects.toThrow(
        'Transform transform.js must export a function, have a default export as a function, or export the specified function "undefined"',
      );
      expect(logger.error).toHaveBeenCalledWith(
        'Error loading transform function from file',
        expect.objectContaining({
          transform: FILE_TRANSFORM_LABEL,
        }),
      );
    });

    it('transforms output using a Python file', async () => {
      const output = 'hello';
      const context = { vars: { key: 'value' }, prompt: { id: '123' } };
      const pythonFilePath = 'file://transform.py';

      const transformedOutput = await transform(pythonFilePath, output, context);
      expect(transformedOutput).toBe('HELLO FROM PYTHON');
    });

    it('throws error for unsupported file format', async () => {
      const output = 'test';
      const context = { vars: {}, prompt: {} };
      const unsupportedFilePath = 'file://transform.txt';

      await expect(transform(unsupportedFilePath, output, context)).rejects.toThrow(
        'Unsupported transform file format: file://transform.txt',
      );
      expect(logger.error).toHaveBeenCalledWith(
        'Error loading transform function from file',
        expect.objectContaining({
          message: 'Unsupported transform file format: file://transform.txt',
          transform: FILE_TRANSFORM_LABEL,
        }),
      );
    });

    it('transforms output using a multi-line function', async () => {
      const output = 'hello';
      const context = { vars: { key: 'value' }, prompt: { id: '123' } };
      const multiLineFunction = `
        const uppercased = output.toUpperCase();
        return uppercased + ' WORLD';
      `;

      const transformedOutput = await transform(multiLineFunction, output, context);
      expect(transformedOutput).toBe('HELLO WORLD');
    });

    it('transforms output using a default export function from a file', async () => {
      const output = 'hello';
      const context = { vars: { key: 'value' }, prompt: { id: '123' } };
      mockedImportModule.mockResolvedValueOnce(
        (output: string) => output.toUpperCase() + ' DEFAULT',
      );

      const transformFunctionPath = 'file://transform.js';
      const transformedOutput = await transform(transformFunctionPath, output, context);
      expect(transformedOutput).toBe('HELLO DEFAULT');
    });

    it('transforms output using a named function from a JavaScript file', async () => {
      const output = 'hello';
      const context = { vars: { key: 'value' }, prompt: { id: '123' } };
      // When a function name is specified, importModule returns that specific function
      mockedImportModule.mockResolvedValueOnce((output: string) => output.toUpperCase() + ' NAMED');

      const transformFunctionPath = 'file://transform.js:namedFunction';
      const transformedOutput = await transform(transformFunctionPath, output, context);
      expect(transformedOutput).toBe('HELLO NAMED');
    });

    it('transforms output using a named function from a Python file', async () => {
      const output = 'hello';
      const context = { vars: { key: 'value' }, prompt: { id: '123' } };
      const pythonFilePath = 'file://transform.py:custom_transform';

      const transformedOutput = await transform(pythonFilePath, output, context);
      expect(transformedOutput).toBe('HELLO FROM PYTHON');
      expect(runPython).toHaveBeenCalledWith(
        expect.stringContaining('transform.py'),
        'custom_transform',
        [output, expect.any(Object)],
      );
    });

    it('falls back to get_transform for Python files when no function name is provided', async () => {
      const output = 'hello';
      const context = { vars: { key: 'value' }, prompt: { id: '123' } };
      const pythonFilePath = 'file://transform.py';

      const transformedOutput = await transform(pythonFilePath, output, context);
      expect(transformedOutput).toBe('HELLO FROM PYTHON');
      expect(runPython).toHaveBeenCalledWith(
        expect.stringContaining('transform.py'),
        'get_transform',
        [output, expect.any(Object)],
      );
    });

    it('does not throw error when validateReturn is false and function returns undefined', async () => {
      const output = 'test';
      const context = { vars: {}, prompt: {} };
      const transformFunction = ''; // Empty function, returns undefined
      const result = await transform(transformFunction, output, context, false);
      expect(result).toBeUndefined();
    });

    it('throws error when validateReturn is true and function returns undefined', async () => {
      const output = 'test';
      const context = { vars: {}, prompt: {} };
      const transformFunction = ''; // Empty function, returns undefined
      await expect(transform(transformFunction, output, context, true)).rejects.toThrow(
        'Transform function did not return a value',
      );
    });

    it('does not throw error when validateReturn is false and function returns null', async () => {
      const output = 'test';
      const context = { vars: {}, prompt: {} };
      const transformFunction = 'null'; // Will be wrapped with "return" automatically
      const result = await transform(transformFunction, output, context, false);
      expect(result).toBeNull();
    });

    it('throws error when validateReturn is true and function returns null', async () => {
      const output = 'test';
      const context = { vars: {}, prompt: {} };
      const transformFunction = 'null'; // Will be wrapped with "return" automatically
      await expect(transform(transformFunction, output, context, true)).rejects.toThrow(
        'Transform function did not return a value',
      );
    });

    it('handles file transform function errors gracefully', async () => {
      const output = 'test';
      const context = { vars: {}, prompt: {} };
      const errorMessage = 'File not found';

      mockedImportModule.mockRejectedValueOnce(new Error(errorMessage));

      const transformFunctionPath = 'file://transform.js';
      await expect(transform(transformFunctionPath, output, context)).rejects.toThrow(errorMessage);
      expect(logger.error).toHaveBeenCalledWith(
        'Error loading transform function from file',
        expect.objectContaining({
          message: errorMessage,
          transform: FILE_TRANSFORM_LABEL,
        }),
      );
    });

    it('handles inline transform function errors gracefully', async () => {
      const output = 'test';
      const context = { vars: {}, prompt: {} };
      const invalidFunction = 'invalid javascript code {';

      await expect(transform(invalidFunction, output, context)).rejects.toThrow(
        'Unexpected identifier',
      );
      expect(logger.error).toHaveBeenCalledWith(
        'Error creating inline transform function',
        expect.objectContaining({
          transform: expect.stringContaining(INLINE_STRING_LABEL),
        }),
      );
    });

    describe('ESM compatibility', () => {
      it('provides process.mainModule.require for backwards compatibility with CommonJS patterns', async () => {
        const output = 'test';
        const context = { vars: {}, prompt: {} };
        // This is the exact pattern users were using before ESM migration
        // const require = process.mainModule.require;
        const transformFunction = `
          const require = process.mainModule.require;
          const path = require('node:path');
          return path.basename('/foo/bar/baz.txt');
        `;
        const result = await transform(transformFunction, output, context);
        expect(result).toBe('baz.txt');
      });

      it('allows direct use of process.mainModule.require without assignment', async () => {
        const output = 'hello';
        const context = { vars: {}, prompt: {} };
        const transformFunction = `
          const fs = process.mainModule.require('node:fs');
          const os = process.mainModule.require('node:os');
          return typeof fs.existsSync === 'function' && typeof os.homedir === 'function' ? output.toUpperCase() : output;
        `;
        const result = await transform(transformFunction, output, context);
        expect(result).toBe('HELLO');
      });

      it('preserves other process properties like process.env', async () => {
        const output = 'test';
        const context = { vars: {}, prompt: {} };
        const transformFunction = `
          // process.env should still work
          const env = process.env;
          return typeof env === 'object' ? 'env-works' : 'env-broken';
        `;
        const result = await transform(transformFunction, output, context);
        expect(result).toBe('env-works');
      });
    });

    describe('file path handling', () => {
      it('handles absolute paths in transform files', async () => {
        const output = 'hello';
        const context = { vars: { key: 'value' }, prompt: { id: '123' } };

        mockedImportModule.mockResolvedValueOnce((output: string) => output.toUpperCase());

        const transformFunctionPath = 'file://transform.js';
        const transformedOutput = await transform(transformFunctionPath, output, context);
        expect(transformedOutput).toBe('HELLO');
      });

      it('handles file URLs in transform files', async () => {
        const output = 'hello';
        const context = { vars: { key: 'value' }, prompt: { id: '123' } };

        mockedImportModule.mockResolvedValueOnce((output: string) => output.toUpperCase());

        const transformFunctionPath = 'file://transform.js';
        const transformedOutput = await transform(transformFunctionPath, output, context);
        expect(transformedOutput).toBe('HELLO');
      });

      it('handles Python files with absolute paths', async () => {
        const output = 'hello';
        const context = { vars: { key: 'value' }, prompt: { id: '123' } };
        const pythonFilePath = 'file://transform.py';

        const transformedOutput = await transform(pythonFilePath, output, context);
        expect(transformedOutput).toBe('HELLO FROM PYTHON');
        expect(runPython).toHaveBeenCalledWith(
          expect.stringContaining('transform.py'),
          'get_transform',
          [output, expect.any(Object)],
        );
      });

      it('handles complex nested paths', async () => {
        const output = 'hello';
        const context = { vars: { key: 'value' }, prompt: { id: '123' } };

        mockedImportModule.mockResolvedValueOnce((output: string) => output.toUpperCase());

        const transformFunctionPath = 'file://deeply/nested/path/with spaces/transform.js';
        const transformedOutput = await transform(transformFunctionPath, output, context);
        expect(transformedOutput).toBe('HELLO');
      });

      it('handles paths with special characters', async () => {
        const output = 'hello';
        const context = { vars: { key: 'value' }, prompt: { id: '123' } };

        mockedImportModule.mockResolvedValueOnce((output: string) => output.toUpperCase());

        const transformFunctionPath = 'file://path/with-hyphens/and_underscores/transform.js';
        const transformedOutput = await transform(transformFunctionPath, output, context);
        expect(transformedOutput).toBe('HELLO');
      });
    });

    describe('inline function transforms (Node.js package)', () => {
      it('transforms output using a directly passed function', async () => {
        const output = 'hello world';
        const context = { vars: { key: 'value' }, prompt: { id: '123' } };
        const fn: TransformFunction = (output) => String(output).toUpperCase();

        const result = await transform(fn, output, context);
        expect(result).toBe('HELLO WORLD');
      });

      it('transforms output using an async function', async () => {
        const output = 'hello';
        const context = { vars: {}, prompt: {} };
        const fn: TransformFunction = async (output) => {
          return output + ' async';
        };

        const result = await transform(fn, output, context);
        expect(result).toBe('hello async');
      });

      it('passes context to the function', async () => {
        const output = 'test';
        const context = { vars: { name: 'Alice' }, prompt: { label: 'greeting' } };
        const fn: TransformFunction = (output, ctx: any) => `${output} for ${ctx.vars.name}`;

        const result = await transform(fn, output, context);
        expect(result).toBe('test for Alice');
      });

      it('transforms vars using a directly passed function', async () => {
        const vars = { key: 'value', other: 'data' };
        const context = { vars: {}, prompt: {} };
        const fn: TransformFunction = (vars: any) => ({ ...vars, key: vars.key.toUpperCase() });

        const result = await transform(fn, vars, context, true, TransformInputType.VARS);
        expect(result).toEqual({ key: 'VALUE', other: 'data' });
      });

      it('throws when inline function returns undefined and validateReturn is true', async () => {
        const output = 'test';
        const context = { vars: {}, prompt: {} };
        const fn: TransformFunction = () => undefined as any;

        await expect(transform(fn, output, context, true)).rejects.toThrow(
          'Transform function did not return a value',
        );
      });

      it('does not throw when inline function returns undefined and validateReturn is false', async () => {
        const output = 'test';
        const context = { vars: {}, prompt: {} };
        const fn: TransformFunction = () => undefined as any;

        const result = await transform(fn, output, context, false);
        expect(result).toBeUndefined();
      });

      it('handles function that accesses metadata from context', async () => {
        const output = 'raw output';
        const context = {
          vars: {},
          prompt: {},
          metadata: { toolCalls: [{ name: 'search' }, { name: 'calculate' }] },
        };
        const fn: TransformFunction = (_output, ctx: any) => {
          const tools = ctx.metadata?.toolCalls ?? [];
          return tools.map((t: any) => t.name).join(', ');
        };

        const result = await transform(fn, output, context);
        expect(result).toBe('search, calculate');
      });

      it('propagates errors thrown by inline functions', async () => {
        const fn: TransformFunction = () => {
          throw new Error('user transform error');
        };

        await expect(transform(fn, 'test', { vars: {}, prompt: {} })).rejects.toThrow(
          'user transform error',
        );
        expect(logger.error).toHaveBeenCalledWith(
          'Error in transform function',
          expect.objectContaining({
            message: 'user transform error',
            transform: expect.stringContaining(INLINE_FUNCTION_LABEL),
          }),
        );
      });

      it('wraps thrown errors with the transform label and preserves the original via cause', async () => {
        const original = new Error('raw user error');
        const fn: TransformFunction = () => {
          throw original;
        };

        try {
          await transform(fn, 'test', { vars: {}, prompt: {} });
          throw new Error('expected transform to throw');
        } catch (err) {
          expect(err).toBeInstanceOf(Error);
          const e = err as Error & { cause?: unknown };
          // Wrapped message includes the label AND the original error text.
          expect(e.message).toContain('Transform failed (');
          expect(e.message).toContain(INLINE_FUNCTION_LABEL);
          expect(e.message).toContain('raw user error');
          // The original error is attached via the standard `cause` chain.
          expect(e.cause).toBe(original);
        }
      });

      it('resolves thenables returned by inline functions', async () => {
        // Bare thenable built via Object.defineProperty to dodge the `noThenProperty`
        // lint rule; verifies `transform()` awaits anything Promise-like.
        const thenable = Object.defineProperty({}, 'then', {
          value: (resolve: (value: unknown) => void) => resolve('thenable-resolved'),
          enumerable: true,
        }) as unknown as Promise<string>;
        const fn: TransformFunction = () => thenable;

        const result = await transform(fn, 'ignored', { vars: {}, prompt: {} });
        expect(result).toBe('thenable-resolved');
      });
    });

    describe('getTransformErrorMessage', () => {
      it('returns the raw message from a transform-wrapped Error via .cause', () => {
        const raw = new Error('underlying boom');
        const wrapped = new Error('Transform failed ([inline function]: fn): underlying boom');
        (wrapped as Error & { cause?: unknown }).cause = raw;
        expect(getTransformErrorMessage(wrapped)).toBe('underlying boom');
      });

      it('falls back to the error message when there is no cause', () => {
        expect(getTransformErrorMessage(new Error('plain'))).toBe('plain');
      });

      it('stringifies non-Error throw values', () => {
        expect(getTransformErrorMessage('just a string')).toBe('just a string');
        expect(getTransformErrorMessage(42)).toBe('42');
      });

      it('returns the outer message when the cause is not an Error', () => {
        const wrapped = new Error('outer');
        (wrapped as Error & { cause?: unknown }).cause = 'a string cause';
        expect(getTransformErrorMessage(wrapped)).toBe('outer');
      });
    });

    describe('getTransformLabel', () => {
      it('shows inline string transforms verbatim', () => {
        expect(getTransformLabel('output.toUpperCase()')).toBe(
          `${INLINE_STRING_LABEL}: output.toUpperCase()`,
        );
      });

      it('collapses whitespace in multi-line inline strings', () => {
        expect(getTransformLabel('const x = output;\n  return x.trim();')).toBe(
          `${INLINE_STRING_LABEL}: const x = output; return x.trim();`,
        );
      });

      it('truncates long inline string transforms', () => {
        const longExpr = 'output.' + 'a'.repeat(200);
        const label = getTransformLabel(longExpr);
        expect(label.startsWith(`${INLINE_STRING_LABEL}: `)).toBe(true);
        expect(label.endsWith('…')).toBe(true);
        expect(label.length).toBeLessThan(longExpr.length);
      });

      it('does not truncate an inline string exactly at the max length', () => {
        const exprAtLimit = 'a'.repeat(80);
        expect(getTransformLabel(exprAtLimit)).toBe(`${INLINE_STRING_LABEL}: ${exprAtLimit}`);
      });

      it('truncates an inline string one character over the max length', () => {
        const exprOverLimit = 'a'.repeat(81);
        const label = getTransformLabel(exprOverLimit);
        // Label body is 79 chars + ellipsis → total 80 chars after the prefix.
        expect(label).toBe(`${INLINE_STRING_LABEL}: ${'a'.repeat(79)}…`);
      });

      it('redacts file transform paths', () => {
        expect(getTransformLabel('file://transform.js')).toBe(FILE_TRANSFORM_LABEL);
      });

      it('does not render function source in error labels', async () => {
        const secretFn = function SECRET_SHOULD_NOT_APPEAR_IN_LABEL() {
          return undefined;
        };
        await expect(transform(secretFn as any, 'test', { vars: {}, prompt: {} })).rejects.toThrow(
          `Transform function did not return a value\n\n${INLINE_FUNCTION_LABEL}: SECRET_SHOULD_NOT_APPEAR_IN_LABEL`,
        );
      });

      it('returns [inline function] for anonymous functions', () => {
        expect(getTransformLabel(() => 'x')).toBe(INLINE_FUNCTION_LABEL);
      });

      it('includes function name for named functions', () => {
        function myTransform() {
          return 'x';
        }
        expect(getTransformLabel(myTransform)).toBe(`${INLINE_FUNCTION_LABEL}: myTransform`);
      });

      it('falls back to inline label for null or undefined inputs', () => {
        expect(getTransformLabel(undefined)).toBe(INLINE_STRING_LABEL);
        expect(getTransformLabel(null)).toBe(INLINE_STRING_LABEL);
      });
    });
  });
});