esphome/script/determine-jobs.py

#!/usr/bin/env python3
"""Determine which CI jobs should run based on changed files.

This script is a centralized way to determine which CI jobs need to run based on
what files have changed. It outputs JSON with the following structure:

{
  "integration_tests": true/false,
  "clang_tidy": true/false,
  "clang_format": true/false,
  "python_linters": true/false,
  "changed_components": ["component1", "component2", ...],
  "component_test_count": 5,
  "memory_impact": {
    "should_run": "true/false",
    "components": ["component1", "component2", ...],
    "platform": "esp32-idf",
    "use_merged_config": "true"
  }
}

The CI workflow uses this information to:
- Skip or run integration tests
- Skip or run clang-tidy (and whether to do a full scan)
- Skip or run clang-format
- Skip or run Python linters (ruff, flake8, pylint, pyupgrade)
- Determine which components to test individually
- Decide how to split component tests (if there are many)
- Run memory impact analysis whenever there are changed components (merged config), and also for core-only changes

Usage:
  python script/determine-jobs.py [-b BRANCH]

Options:
  -b, --branch BRANCH  Branch to compare against (default: dev)
"""

from __future__ import annotations

import argparse
from collections import Counter
from enum import StrEnum
from functools import cache
import json
import os
from pathlib import Path
import subprocess
import sys
from typing import Any

from helpers import (
    CPP_FILE_EXTENSIONS,
    ESPHOME_TESTS_COMPONENTS_PATH,
    PYTHON_FILE_EXTENSIONS,
    changed_files,
    core_changed,
    filter_component_and_test_cpp_files,
    filter_component_and_test_files,
    get_all_dependencies,
    get_changed_components,
    get_component_from_path,
    get_component_test_files,
    get_components_from_integration_fixtures,
    get_components_with_dependencies,
    get_cpp_changed_components,
    git_ls_files,
    parse_test_filename,
    root_path,
)
from split_components_for_ci import create_intelligent_batches

# Threshold for splitting clang-tidy jobs
# For small PRs (< 65 files), use nosplit for faster CI
# For large PRs (>= 65 files), use split for better parallelization
CLANG_TIDY_SPLIT_THRESHOLD = 65

# Component test batch size (weighted)
# Isolated components count as 10x, groupable components count as 1x
COMPONENT_TEST_BATCH_SIZE = 40


class Platform(StrEnum):
    """Platform identifiers for memory impact analysis."""

    ESP8266_ARD = "esp8266-ard"
    ESP32_IDF = "esp32-idf"
    ESP32_C3_IDF = "esp32-c3-idf"
    ESP32_C6_IDF = "esp32-c6-idf"
    ESP32_S2_IDF = "esp32-s2-idf"
    ESP32_S3_IDF = "esp32-s3-idf"


# Memory impact analysis constants
MEMORY_IMPACT_FALLBACK_COMPONENT = "api"  # Representative component for core changes
MEMORY_IMPACT_FALLBACK_PLATFORM = Platform.ESP32_IDF  # Most representative platform

# Platform preference order for memory impact analysis
# This order is used when no platform-specific hints are detected from filenames
# Priority rationale:
# 1. ESP32-C6 IDF - Newest platform, supports Thread/Zigbee
# 2. ESP8266 Arduino - Most memory constrained (best for detecting memory impact),
#                      fastest build times, most sensitive to code size changes
# 3. ESP32 IDF - Primary ESP32 platform, most representative of modern ESPHome
# 4-6. Other ESP32 variants - Less commonly used but still supported
MEMORY_IMPACT_PLATFORM_PREFERENCE = [
    Platform.ESP32_C6_IDF,  # ESP32-C6 IDF (newest, supports Thread/Zigbee)
    Platform.ESP8266_ARD,  # ESP8266 Arduino (most memory constrained, fastest builds)
    Platform.ESP32_IDF,  # ESP32 IDF platform (primary ESP32 platform, most representative)
    Platform.ESP32_C3_IDF,  # ESP32-C3 IDF
    Platform.ESP32_S2_IDF,  # ESP32-S2 IDF
    Platform.ESP32_S3_IDF,  # ESP32-S3 IDF
]


def should_run_integration_tests(branch: str | None = None) -> bool:
    """Determine if integration tests should run based on changed files.

    This function is used by the CI workflow to intelligently skip integration tests when they're
    not needed, saving significant CI time and resources.

    Integration tests will run when ANY of the following conditions are met:

    1. Core C++ files changed (esphome/core/*)
       - Any .cpp, .h, .tcc files in the core directory
       - These files contain fundamental functionality used throughout ESPHome
       - Examples: esphome/core/component.cpp, esphome/core/application.h

    2. Core Python files changed (esphome/core/*.py)
       - Only .py files in the esphome/core/ directory
       - These are core Python files that affect the entire system
       - Examples: esphome/core/config.py, esphome/core/__init__.py
       - NOT included: esphome/*.py, esphome/dashboard/*.py, esphome/components/*/*.py

    3. Integration test files changed
       - Any file in tests/integration/ directory
       - This includes test files themselves and fixture YAML files
       - Examples: tests/integration/test_api.py, tests/integration/fixtures/api.yaml

    4. Components used by integration tests (or their dependencies) changed
       - The function parses all YAML files in tests/integration/fixtures/
       - Extracts which components are used in integration tests
       - Recursively finds all dependencies of those components
       - If any of these components have changes, tests must run
       - Example: If api.yaml uses 'sensor' and 'api' components, and 'api' depends on 'socket',
         then changes to sensor/, api/, or socket/ components trigger tests

    Args:
        branch: Branch to compare against. If None, uses default.

    Returns:
        True if integration tests should run, False otherwise.
    """
    files = changed_files(branch)

    if core_changed(files):
        # If any core files changed, run integration tests
        return True

    # Check if any integration test files changed
    if any("tests/integration" in file for file in files):
        return True

    # Get all components used in integration tests and their dependencies
    fixture_components = get_components_from_integration_fixtures()
    all_required_components = get_all_dependencies(fixture_components)

    # Check if any required components changed
    for file in files:
        component = get_component_from_path(file)
        if component and component in all_required_components:
            return True

    return False


@cache
def _is_clang_tidy_full_scan() -> bool:
    """Check if clang-tidy configuration changed (requires full scan).

    Returns:
        True if full scan is needed (hash changed), False otherwise.
    """
    try:
        result = subprocess.run(
            [os.path.join(root_path, "script", "clang_tidy_hash.py"), "--check"],
            capture_output=True,
            check=False,
        )
        # Exit 0 means hash changed (full scan needed)
        return result.returncode == 0
    except Exception:
        # If hash check fails, run full scan to be safe
        return True


def should_run_clang_tidy(branch: str | None = None) -> bool:
    """Determine if clang-tidy should run based on changed files.

    This function is used by the CI workflow to intelligently skip clang-tidy checks when they're
    not needed, saving significant CI time and resources.

    Clang-tidy will run when ANY of the following conditions are met:

    1. Clang-tidy configuration changed
       - The hash of .clang-tidy configuration file has changed
       - The hash includes the .clang-tidy file, clang-tidy version from requirements_dev.txt,
         and relevant platformio.ini sections
       - When configuration changes, a full scan is needed to ensure all code complies
         with the new rules
       - Detected by script/clang_tidy_hash.py --check returning exit code 0

    2. Any C++ source files changed
       - Any file with C++ extensions: .cpp, .h, .hpp, .cc, .cxx, .c, .tcc
       - Includes files anywhere in the repository, not just in esphome/
       - This ensures all C++ code is checked, including tests, examples, etc.
       - Examples: esphome/core/component.cpp, tests/custom/my_component.h

    3. The .clang-tidy.hash file itself changed
       - This indicates the configuration has been updated and clang-tidy should run
       - Ensures that PRs updating the clang-tidy configuration are properly validated

    If the hash check fails for any reason, clang-tidy runs as a safety measure to ensure
    code quality is maintained.

    Args:
        branch: Branch to compare against. If None, uses default.

    Returns:
        True if clang-tidy should run, False otherwise.
    """
    # First check if clang-tidy configuration changed (full scan needed)
    if _is_clang_tidy_full_scan():
        return True

    # Check if .clang-tidy.hash file itself was changed
    # This handles the case where the hash was properly updated in the PR
    files = changed_files(branch)
    if ".clang-tidy.hash" in files:
        return True

    return _any_changed_file_endswith(branch, CPP_FILE_EXTENSIONS)


def count_changed_cpp_files(branch: str | None = None) -> int:
    """Count the number of changed C++ files.

    This is used to determine whether to split clang-tidy jobs or run them as a single job.
    For PRs with < 65 changed C++ files, running a single job is faster than splitting.

    Args:
        branch: Branch to compare against. If None, uses default.

    Returns:
        Number of changed C++ files.
    """
    files = changed_files(branch)
    return sum(1 for file in files if file.endswith(CPP_FILE_EXTENSIONS))


def should_run_clang_format(branch: str | None = None) -> bool:
    """Determine if clang-format should run based on changed files.

    This function is used by the CI workflow to skip clang-format checks when no C++ files
    have changed, saving CI time and resources.

    Clang-format will run when any C++ source files have changed.

    Args:
        branch: Branch to compare against. If None, uses default.

    Returns:
        True if clang-format should run, False otherwise.
    """
    return _any_changed_file_endswith(branch, CPP_FILE_EXTENSIONS)


def should_run_python_linters(branch: str | None = None) -> bool:
    """Determine if Python linters (ruff, flake8, pylint, pyupgrade) should run based on changed files.

    This function is used by the CI workflow to skip Python linting checks when no Python files
    have changed, saving CI time and resources.

    Python linters will run when any Python source files have changed.

    Args:
        branch: Branch to compare against. If None, uses default.

    Returns:
        True if Python linters should run, False otherwise.
    """
    return _any_changed_file_endswith(branch, PYTHON_FILE_EXTENSIONS)


def determine_cpp_unit_tests(
    branch: str | None = None,
) -> tuple[bool, list[str]]:
    """Determine if C++ unit tests should run based on changed files.

    This function is used by the CI workflow to skip C++ unit tests when
    no relevant files have changed, saving CI time and resources.

    C++ unit tests will run when any of the following conditions are met:

    1. Any C++ core source files changed (esphome/core/*), in which case
       all cpp unit tests run.
    2. A test file for a component changed, which triggers tests for that
       component.
    3. The code for a component changed, which triggers tests for that
       component and all components that depend on it.

    Args:
        branch: Branch to compare against. If None, uses default.

    Returns:
        Tuple of (run_all, components) where:
        - run_all: True if all tests should run, False otherwise
        - components: List of specific components to test (empty if run_all)
    """
    files = changed_files(branch)
    if core_changed(files):
        return (True, [])

    # Filter to only C++ files
    cpp_files = list(filter(filter_component_and_test_cpp_files, files))
    return (False, get_cpp_changed_components(cpp_files))


def _any_changed_file_endswith(branch: str | None, extensions: tuple[str, ...]) -> bool:
    """Check if a changed file ends with any of the specified extensions."""
    return any(file.endswith(extensions) for file in changed_files(branch))


@cache
def _component_has_tests(component: str) -> bool:
    """Check if a component has test files.

    Cached to avoid repeated filesystem operations for the same component.

    Args:
        component: Component name to check

    Returns:
        True if the component has test YAML files
    """
    return bool(get_component_test_files(component, all_variants=True))


def _select_platform_by_preference(
    platforms: list[Platform] | set[Platform],
) -> Platform:
    """Select the most preferred platform from a list/set based on MEMORY_IMPACT_PLATFORM_PREFERENCE.

    Args:
        platforms: List or set of platforms to choose from

    Returns:
        The most preferred platform (earliest in MEMORY_IMPACT_PLATFORM_PREFERENCE)
    """
    return min(platforms, key=MEMORY_IMPACT_PLATFORM_PREFERENCE.index)


def _select_platform_by_count(
    platform_counts: Counter[Platform],
) -> Platform:
    """Select platform by count, using MEMORY_IMPACT_PLATFORM_PREFERENCE as tiebreaker.

    Args:
        platform_counts: Counter mapping platforms to their counts

    Returns:
        Platform with highest count, breaking ties by preference order
    """
    return min(
        platform_counts.keys(),
        key=lambda p: (
            -platform_counts[p],  # Negative to prefer higher counts
            MEMORY_IMPACT_PLATFORM_PREFERENCE.index(p),
        ),
    )


def _detect_platform_hint_from_filename(filename: str) -> Platform | None:
    """Detect platform hint from filename patterns.

    Detects platform-specific files using patterns like:
    - wifi_component_esp_idf.cpp, *_idf.h -> ESP32 IDF variants
    - wifi_component_esp8266.cpp, *_esp8266.h -> ESP8266_ARD
    - *_esp32*.cpp -> ESP32 IDF (generic)
    - *_libretiny.cpp, *_retiny.* -> LibreTiny (not in preference list)
    - *_pico.cpp, *_rp2040.* -> RP2040 (not in preference list)

    Args:
        filename: File path to check

    Returns:
        Platform enum if a specific platform is detected, None otherwise
    """
    filename_lower = filename.lower()

    # ESP-IDF platforms (check specific variants first)
    if "esp_idf" in filename_lower or "_idf" in filename_lower:
        # Check for specific ESP32 variants
        if "c6" in filename_lower or "esp32c6" in filename_lower:
            return Platform.ESP32_C6_IDF
        if "c3" in filename_lower or "esp32c3" in filename_lower:
            return Platform.ESP32_C3_IDF
        if "s2" in filename_lower or "esp32s2" in filename_lower:
            return Platform.ESP32_S2_IDF
        if "s3" in filename_lower or "esp32s3" in filename_lower:
            return Platform.ESP32_S3_IDF
        # Default to ESP32 IDF for generic esp_idf files
        return Platform.ESP32_IDF

    # ESP8266 Arduino
    if "esp8266" in filename_lower:
        return Platform.ESP8266_ARD

    # Generic ESP32 (without _idf suffix, could be Arduino or shared code)
    # Prefer IDF as it's the modern platform
    if "esp32" in filename_lower:
        return Platform.ESP32_IDF

    # LibreTiny and RP2040 are not in MEMORY_IMPACT_PLATFORM_PREFERENCE
    # so we don't return them as hints
    # if "retiny" in filename_lower or "libretiny" in filename_lower:
    #     return None  # No specific LibreTiny platform preference
    # if "pico" in filename_lower or "rp2040" in filename_lower:
    #     return None  # No RP2040 platform preference

    return None


def detect_memory_impact_config(
    branch: str | None = None,
) -> dict[str, Any]:
    """Determine memory impact analysis configuration.

    Always runs memory impact analysis when there are changed components,
    building a merged configuration with all changed components (like
    test_build_components.py does) to get comprehensive memory analysis.

    When platform-specific files are detected (e.g., wifi_component_esp_idf.cpp),
    prefers that platform for testing to ensure the most relevant memory analysis.

    For core C++ file changes without component changes, runs a fallback
    analysis using a representative component to measure the impact.

    Args:
        branch: Branch to compare against

    Returns:
        Dictionary with memory impact analysis parameters:
        - should_run: "true" or "false"
        - components: list of component names to analyze
        - platform: platform name for the merged build
        - use_merged_config: "true" (always use merged config)
    """

    # Get actually changed files (not dependencies)
    files = changed_files(branch)

    # Find all changed components (excluding core)
    # Also collect platform hints from platform-specific filenames
    changed_component_set: set[str] = set()
    has_core_cpp_changes = False
    platform_hints: list[Platform] = []

    for file in files:
        component = get_component_from_path(file)
        if component:
            # Add all changed components, including base bus components
            # Base bus components (uart, i2c, spi, etc.) should still be analyzed
            # when directly changed, even though they're also used as dependencies
            changed_component_set.add(component)
            # Check if this is a platform-specific file
            if platform_hint := _detect_platform_hint_from_filename(file):
                platform_hints.append(platform_hint)
        elif file.startswith("esphome/") and file.endswith(CPP_FILE_EXTENSIONS):
            # Core ESPHome C++ files changed (not component-specific)
            # Only C++ files affect memory usage
            has_core_cpp_changes = True

    # If no components changed but core C++ changed, test representative component
    force_fallback_platform = False
    if not changed_component_set and has_core_cpp_changes:
        print(
            f"Memory impact: No components changed, but core C++ files changed. "
            f"Testing {MEMORY_IMPACT_FALLBACK_COMPONENT} component on {MEMORY_IMPACT_FALLBACK_PLATFORM}.",
            file=sys.stderr,
        )
        changed_component_set.add(MEMORY_IMPACT_FALLBACK_COMPONENT)
        force_fallback_platform = True  # Use fallback platform (most representative)
    elif not changed_component_set:
        # No components and no core C++ changes
        return {"should_run": "false"}

    # Find components that have tests and collect their supported platforms
    components_with_tests: list[str] = []
    component_platforms_map: dict[
        str, set[Platform]
    ] = {}  # Track which platforms each component supports

    for component in sorted(changed_component_set):
        # Look for test files on preferred platforms
        test_files = get_component_test_files(component, all_variants=True)
        if not test_files:
            continue

        # Check if component has tests for any preferred platform
        available_platforms = [
            platform
            for test_file in test_files
            if (platform := parse_test_filename(test_file)[1]) != "all"
            and platform in MEMORY_IMPACT_PLATFORM_PREFERENCE
        ]

        if not available_platforms:
            continue

        component_platforms_map[component] = set(available_platforms)
        components_with_tests.append(component)

    # If no components have tests, don't run memory impact
    if not components_with_tests:
        return {"should_run": "false"}

    # Find common platforms supported by ALL components
    # This ensures we can build all components together in a merged config
    common_platforms = set(MEMORY_IMPACT_PLATFORM_PREFERENCE)
    for component, platforms in component_platforms_map.items():
        common_platforms &= platforms

    # Select the most preferred platform from the common set
    # Priority order:
    # 1. Platform hints from filenames (e.g., wifi_component_esp_idf.cpp suggests ESP32_IDF)
    # 2. Core changes use fallback platform (most representative of codebase)
    # 3. Common platforms supported by all components
    # 4. Most commonly supported platform
    if platform_hints:
        # Use most common platform hint that's also supported by all components
        hint_counts = Counter(platform_hints)
        # Filter to only hints that are in common_platforms (if any common platforms exist)
        valid_hints = (
            [h for h in hint_counts if h in common_platforms]
            if common_platforms
            else list(hint_counts.keys())
        )
        if valid_hints:
            platform = _select_platform_by_count(
                Counter({p: hint_counts[p] for p in valid_hints})
            )
        elif common_platforms:
            # Hints exist but none match common platforms, use common platform logic
            platform = _select_platform_by_preference(common_platforms)
        else:
            # Use the most common hint even if it's not in common platforms
            platform = _select_platform_by_count(hint_counts)
    elif force_fallback_platform:
        platform = MEMORY_IMPACT_FALLBACK_PLATFORM
    elif common_platforms:
        # Pick the most preferred platform that all components support
        platform = _select_platform_by_preference(common_platforms)
    else:
        # No common platform - pick the most commonly supported platform
        # Count how many components support each platform
        platform_counts = Counter(
            p for platforms in component_platforms_map.values() for p in platforms
        )
        platform = _select_platform_by_count(platform_counts)

    # Debug output
    print("Memory impact analysis:", file=sys.stderr)
    print(f"  Changed components: {sorted(changed_component_set)}", file=sys.stderr)
    print(f"  Components with tests: {components_with_tests}", file=sys.stderr)
    print(
        f"  Component platforms: {dict(sorted(component_platforms_map.items()))}",
        file=sys.stderr,
    )
    print(f"  Platform hints from filenames: {platform_hints}", file=sys.stderr)
    print(f"  Common platforms: {sorted(common_platforms)}", file=sys.stderr)
    print(f"  Selected platform: {platform}", file=sys.stderr)

    return {
        "should_run": "true",
        "components": components_with_tests,
        "platform": platform,
        "use_merged_config": "true",
    }


def main() -> None:
    """Main function that determines which CI jobs to run."""
    parser = argparse.ArgumentParser(
        description="Determine which CI jobs should run based on changed files"
    )
    parser.add_argument(
        "-b", "--branch", help="Branch to compare changed files against"
    )
    args = parser.parse_args()

    # Determine what should run
    run_integration = should_run_integration_tests(args.branch)
    run_clang_tidy = should_run_clang_tidy(args.branch)
    run_clang_format = should_run_clang_format(args.branch)
    run_python_linters = should_run_python_linters(args.branch)
    changed_cpp_file_count = count_changed_cpp_files(args.branch)

    # Get changed components
    # get_changed_components() returns:
    #   None: Core files changed (need full scan)
    #   []: No components changed
    #   [list]: Changed components (already includes dependencies)
    changed_components_result = get_changed_components()

    # Always analyze component files, even if core files changed
    # This is needed for component testing and memory impact analysis
    changed = changed_files(args.branch)
    component_files = [f for f in changed if filter_component_and_test_files(f)]

    directly_changed_components = get_components_with_dependencies(
        component_files, False
    )

    if changed_components_result is None:
        # Core files changed - will trigger full clang-tidy scan
        # But we still need to track changed components for testing and memory analysis
        changed_components = get_components_with_dependencies(component_files, True)
        is_core_change = True
    else:
        # Use the result from get_changed_components() which includes dependencies
        changed_components = changed_components_result
        is_core_change = False

    # Filter to only components that have test files
    # Components without tests shouldn't generate CI test jobs
    changed_components_with_tests = [
        component for component in changed_components if _component_has_tests(component)
    ]

    # Get directly changed components with tests (for isolated testing)
    # These will be tested WITHOUT --testing-mode in CI to enable full validation
    # (pin conflicts, etc.) since they contain the actual changes being reviewed
    directly_changed_with_tests = {
        component
        for component in directly_changed_components
        if _component_has_tests(component)
    }

    # Get dependency-only components (for grouped testing)
    dependency_only_components = [
        component
        for component in changed_components_with_tests
        if component not in directly_changed_components
    ]

    # Detect components for memory impact analysis (merged config)
    memory_impact = detect_memory_impact_config(args.branch)

    # Determine clang-tidy mode based on actual files that will be checked
    if run_clang_tidy:
        # Full scan needed if: hash changed OR core files changed
        is_full_scan = _is_clang_tidy_full_scan() or is_core_change

        if is_full_scan:
            # Full scan checks all files - always use split mode for efficiency
            clang_tidy_mode = "split"
            files_to_check_count = -1  # Sentinel value for "all files"
        else:
            # Targeted scan - calculate actual files that will be checked
            # This accounts for component dependencies, not just directly changed files
            if changed_components:
                # Count C++ files in all changed components (including dependencies)
                all_cpp_files = list(git_ls_files(["*.cpp"]).keys())
                component_set = set(changed_components)
                files_to_check_count = sum(
                    1
                    for f in all_cpp_files
                    if get_component_from_path(f) in component_set
                )
            else:
                # If no components changed, use the simple count of changed C++ files
                files_to_check_count = changed_cpp_file_count

            if files_to_check_count < CLANG_TIDY_SPLIT_THRESHOLD:
                clang_tidy_mode = "nosplit"
            else:
                clang_tidy_mode = "split"
    else:
        clang_tidy_mode = "disabled"
        files_to_check_count = 0

    # Build output
    # Determine which C++ unit tests to run
    cpp_run_all, cpp_components = determine_cpp_unit_tests(args.branch)

    # Split components into batches for CI testing
    # This intelligently groups components with similar bus configurations
    component_test_batches: list[str]
    if changed_components_with_tests:
        tests_dir = Path(root_path) / ESPHOME_TESTS_COMPONENTS_PATH
        batches, _ = create_intelligent_batches(
            components=changed_components_with_tests,
            tests_dir=tests_dir,
            batch_size=COMPONENT_TEST_BATCH_SIZE,
            directly_changed=directly_changed_with_tests,
        )
        # Convert batches to space-separated strings for CI matrix
        component_test_batches = [" ".join(batch) for batch in batches]
    else:
        component_test_batches = []

    output: dict[str, Any] = {
        "integration_tests": run_integration,
        "clang_tidy": run_clang_tidy,
        "clang_tidy_mode": clang_tidy_mode,
        "clang_format": run_clang_format,
        "python_linters": run_python_linters,
        "changed_components": changed_components,
        "changed_components_with_tests": changed_components_with_tests,
        "directly_changed_components_with_tests": list(directly_changed_with_tests),
        "dependency_only_components_with_tests": dependency_only_components,
        "component_test_count": len(changed_components_with_tests),
        "directly_changed_count": len(directly_changed_with_tests),
        "dependency_only_count": len(dependency_only_components),
        "changed_cpp_file_count": changed_cpp_file_count,
        "memory_impact": memory_impact,
        "cpp_unit_tests_run_all": cpp_run_all,
        "cpp_unit_tests_components": cpp_components,
        "component_test_batches": component_test_batches,
    }

    # Output as JSON
    print(json.dumps(output))


if __name__ == "__main__":
    main()