#!/usr/bin/env python3
"""
test-suite-generator.py — Auto-generate pytest tests for uncovered functions.

Scans Python files in a repo, identifies public functions/methods without tests,
and generates pytest test stubs with edge cases.

Usage:
    python3 scripts/test-suite-generator.py --repo ~/repos/my-project
    python3 scripts/test-suite-generator.py --repo ~/repos/my-project --output tests/test_genome_generated.py
    python3 scripts/test-suite-generator.py --repo ~/repos/my-project --dry-run
"""

import ast
import argparse
import os
import sys
from pathlib import Path
from dataclasses import dataclass, field
from typing import Optional

SKIP_DIRS = {"node_modules", ".git", "__pycache__", "venv", ".venv", "dist", "build", ".tox", ".mypy_cache"}
SKIP_FILES = {"test_", "conftest", "setup", "__init__", "manage", "wsgi", "asgi"}


@dataclass
class FunctionInfo:
    name: str
    file_path: str
    line_number: int
    class_name: Optional[str] = None
    args: list = field(default_factory=list)
    is_async: bool = False
    docstring: Optional[str] = None
    has_return: bool = False
    has_try_except: bool = False
    decorators: list = field(default_factory=list)


def scan_file(filepath: Path) -> list[FunctionInfo]:
    """Extract function definitions from a Python file."""
    try:
        source = filepath.read_text(errors="ignore")
        tree = ast.parse(source, filename=str(filepath))
    except (SyntaxError, UnicodeDecodeError):
        return []

    functions = []
    current_class = None

    for node in ast.walk(tree):
        if isinstance(node, ast.ClassDef):
            current_class = node.name
            continue

        if not isinstance(node, (ast.FunctionDef, ast.AsyncFunctionDef)):
            continue

        # Skip private/internal functions
        if node.name.startswith("_") and node.name != "__init__":
            continue

        # Extract args (skip 'self')
        args = [arg.arg for arg in node.args.args if arg.arg != "self"]

        # Check for return statements
        has_return = any(
            isinstance(n, ast.Return) and n.value is not None
            for n in ast.walk(node)
        )

        # Check for try/except
        has_try_except = any(
            isinstance(n, ast.Try)
            for n in ast.walk(node)
        )

        # Extract decorators
        decorators = []
        for dec in node.decorator_list:
            if isinstance(dec, ast.Name):
                decorators.append(dec.id)
            elif isinstance(dec, ast.Attribute):
                decorators.append(dec.attr)

        # Docstring
        docstring = ast.get_docstring(node)

        functions.append(FunctionInfo(
            name=node.name,
            file_path=str(filepath),
            line_number=node.lineno,
            class_name=current_class,
            args=args,
            is_async=isinstance(node, ast.AsyncFunctionDef),
            docstring=docstring,
            has_return=has_return,
            has_try_except=has_try_except,
            decorators=decorators,
        ))

        current_class = None  # Reset after function

    return functions


def scan_repo(repo_path: Path) -> list[FunctionInfo]:
    """Scan all Python files in a repo."""
    all_functions = []

    for root, dirs, files in os.walk(repo_path):
        dirs[:] = [d for d in dirs if d not in SKIP_DIRS]
        for fname in sorted(files):
            if not fname.endswith(".py"):
                continue
            if any(fname.startswith(skip) for skip in SKIP_FILES):
                continue

            filepath = Path(root) / fname
            functions = scan_file(filepath)
            all_functions.extend(functions)

    return all_functions


def find_existing_tests(repo_path: Path) -> set[str]:
    """Find function names that already have test coverage."""
    tested = set()

    for root, dirs, files in os.walk(repo_path):
        dirs[:] = [d for d in dirs if d not in SKIP_DIRS]
        for fname in files:
            if not fname.startswith("test_") or not fname.endswith(".py"):
                continue
            filepath = Path(root) / fname
            try:
                source = filepath.read_text(errors="ignore")
                # Look for test_functionname patterns
                import re
                for match in re.finditer(r"def test_(\w+)", source):
                    tested.add(match.group(1))
            except OSError:
                pass

    return tested


def generate_test(func: FunctionInfo, repo_path: Path) -> str:
    """Generate a pytest test for a function."""
    rel_path = Path(func.file_path).relative_to(repo_path)
    module_path = str(rel_path).replace("/", ".").replace(".py", "")

    # Build import
    if func.class_name:
        import_line = f"from {module_path} import {func.class_name}"
        call_prefix = f"{func.class_name}()."
    else:
        import_line = f"from {module_path} import {func.name}"
        call_prefix = ""

    func_qualified = f"{call_prefix}{func.name}"
    test_name = f"test_{func.name}"
    if func.class_name:
        test_name = f"test_{func.class_name}_{func.name}"

    lines = []
    lines.append(f"")
    lines.append(f"def {test_name}():")
    if func.docstring:
        lines.append(f'    """Auto-generated test for {func.name}."""')
    else:
        lines.append(f'    """Auto-generated test."""')

    # Build args
    arg_strs = []
    for arg in func.args:
        if arg in ("self", "cls"):
            continue
        if arg in ("text", "content", "message", "data", "input", "name", "path", "url"):
            arg_strs.append(f'"{arg}_value"')
        elif arg in ("count", "n", "limit", "size", "length", "index", "port", "timeout"):
            arg_strs.append("1")
        elif arg in ("items", "values", "args", "kwargs", "options", "params"):
            arg_strs.append("{}")
        elif arg in ("enabled", "verbose", "quiet", "force", "debug", "dry_run"):
            arg_strs.append("False")
        else:
            arg_strs.append("None")

    args_joined = ", ".join(arg_strs)

    # Generate test body
    if func.has_try_except:
        lines.append(f"    # Function has try/except — test error handling")
        lines.append(f"    try:")
        lines.append(f"        result = {func_qualified}({args_joined})")
        lines.append(f"    except Exception:")
        lines.append(f"        pass  # Expected behavior for edge case input")
    elif func.has_return:
        lines.append(f"    result = {func_qualified}({args_joined})")
        lines.append(f"    assert result is not None or result is None  # Placeholder — refine with domain knowledge")
    elif func.is_async:
        lines.append(f"    import asyncio")
        lines.append(f"    # result = asyncio.run({func_qualified}({args_joined}))")
        lines.append(f"    pass  # Async function — needs proper test setup")
    else:
        lines.append(f"    # Function returns None — test it doesn't raise")
        lines.append(f"    {func_qualified}({args_joined})")

    lines.append("")
    return "\n".join(lines)


def generate_test_file(functions: list[FunctionInfo], repo_path: Path) -> str:
    """Generate a complete test file."""
    lines = []
    lines.append('"""Auto-generated tests by test-suite-generator.py.')
    lines.append("")
    lines.append("These tests are stubs — they verify functions don't crash on basic inputs.")
    lines.append("Refine with domain-specific assertions for real coverage.")
    lines.append("")
    lines.append(f"Generated: {len(functions)} test stubs")
    lines.append('"""')
    lines.append("")
    lines.append("import pytest")
    lines.append("")

    # Collect unique imports
    imports = set()
    for func in functions:
        rel_path = Path(func.file_path).relative_to(repo_path)
        module_path = str(rel_path).replace("/", ".").replace(".py", "")
        if func.class_name:
            imports.add(f"from {module_path} import {func.class_name}")
        else:
            imports.add(f"from {module_path} import {func.name}")

    for imp in sorted(imports):
        lines.append(imp)

    # Generate tests grouped by file
    current_file = None
    for func in sorted(functions, key=lambda f: (f.file_path, f.line_number)):
        if func.file_path != current_file:
            rel = Path(func.file_path).relative_to(repo_path)
            lines.append("")
            lines.append(f"# --- Tests for {rel} ---")
            current_file = func.file_path

        lines.append(generate_test(func, repo_path))

    return "\n".join(lines)


def main():
    parser = argparse.ArgumentParser(description="Generate pytest tests for uncovered functions")
    parser.add_argument("--repo", required=True, help="Path to repo to scan")
    parser.add_argument("--output", default=None, help="Output file path")
    parser.add_argument("--dry-run", action="store_true", help="Show what would be generated")
    args = parser.parse_args()

    repo_path = Path(args.repo).resolve()
    if not repo_path.exists():
        print(f"Error: {repo_path} not found", file=sys.stderr)
        sys.exit(1)

    print(f"Scanning {repo_path}...", file=sys.stderr)
    all_functions = scan_repo(repo_path)
    tested = find_existing_tests(repo_path)

    untested = [f for f in all_functions if f.name not in tested]
    print(f"Found {len(all_functions)} functions, {len(tested)} already tested, {len(untested)} untested", file=sys.stderr)

    if not untested:
        print("All functions have test coverage!", file=sys.stderr)
        sys.exit(0)

    if args.dry_run:
        print(f"\nWould generate {len(untested)} test stubs:")
        for func in untested[:20]:
            rel = Path(func.file_path).relative_to(repo_path)
            cls = f"{func.class_name}." if func.class_name else ""
            print(f"  {rel}:{func.line_number} {cls}{func.name}({', '.join(func.args)})")
        if len(untested) > 20:
            print(f"  ... and {len(untested) - 20} more")
        sys.exit(0)

    # Generate
    test_content = generate_test_file(untested, repo_path)

    output_path = args.output or str(repo_path / "tests" / "test_genome_generated.py")
    os.makedirs(os.path.dirname(output_path), exist_ok=True)
    Path(output_path).write_text(test_content)
    print(f"Generated {len(untested)} test stubs → {output_path}", file=sys.stderr)


if __name__ == "__main__":
    main()