import fnmatch
import json
import os
from pathlib import Path
import subprocess
import sys
from typing import Iterable, Optional, Mapping

def gha_set_output(vars: Mapping[str, str | Path]):
    """Sets values in a step's output parameters.

    This appends to the file located at the $GITHUB_OUTPUT environment variable.

    See
      * https://docs.github.com/en/actions/reference/workflow-commands-for-github-actions#setting-an-output-parameter
      * https://docs.github.com/en/actions/writing-workflows/choosing-what-your-workflow-does/passing-information-between-jobs
    """
    print(f"Setting github output:\n{vars}")

    step_output_file = os.getenv("GITHUB_OUTPUT")
    if not step_output_file:
        print("  Warning: GITHUB_OUTPUT env var not set, can't set github outputs")
        return

    with open(step_output_file, "a") as f:
        f.writelines(f"{k}={str(v)}" + "\n" for k, v in vars.items())

def get_modified_paths(base_ref: str) -> Optional[Iterable[str]]:
    """Returns the paths of modified files relative to the base reference."""
    try:
        return subprocess.run(
            ["git", "diff", "--name-only", base_ref],
            stdout=subprocess.PIPE,
            check=True,
            text=True,
            timeout=60,
        ).stdout.splitlines()
    except TimeoutError:
        print(
            "Computing modified files timed out. Not using PR diff to determine"
            " jobs to run.",
            file=sys.stderr,
        )
        return None

# Paths matching any of these patterns are considered to have no influence over
# build or test workflows so any related jobs can be skipped if all paths
# modified by a commit/PR match a pattern in this list.
SKIPPABLE_PATH_PATTERNS = [
    "docs/*",
    "*.gitignore",
    "*.md",
    "*.pre-commit-config.*",
    "*LICENSE",
    'Jenkinsfile',
    '.github/ISSUE_TEMPLATE/*',
    '.github/CODEOWNERS',
    '.github/*.md',
    '.github/dependabot.yml',
]

def is_path_skippable(path: str) -> bool:
    """Determines if a given relative path to a file matches any skippable patterns."""
    return any(fnmatch.fnmatch(path, pattern) for pattern in SKIPPABLE_PATH_PATTERNS)

def check_for_non_skippable_path(paths: Optional[Iterable[str]]) -> bool:
    """Returns true if at least one path is not in the skippable set."""
    if paths is None:
        return False
    return any(not is_path_skippable(p) for p in paths)

def should_ci_run_given_modified_paths(paths: Optional[Iterable[str]]) -> bool:
    """Returns true if CI workflows should run given a list of modified paths."""

    if paths is None:
        print("No files were modified, skipping TheRock CI jobs")
        return False

    paths_set = set(paths)
    github_workflows_paths = set(
        [p for p in paths if p.startswith(".github/workflows")]
    )
    other_paths = paths_set - github_workflows_paths

    contains_other_non_skippable_files = check_for_non_skippable_path(other_paths)

    print("should_ci_run_given_modified_paths findings:")
    print(f"  contains_other_non_skippable_files: {contains_other_non_skippable_files}")

    if contains_other_non_skippable_files:
        print("Enabling TheRock CI jobs since a non-skippable path was modified")
        return True
    else:
        print(
            "Only unrelated and/or skippable paths were modified, skipping TheRock CI jobs"
        )
        return False

def main(args):
    base_ref = args.get("base_ref")
    modified_paths = get_modified_paths(base_ref)
    print("modified_paths (max 200):", modified_paths[:200])
    enable_jobs = should_ci_run_given_modified_paths(modified_paths)
    output = {
        'enable_therock_ci': json.dumps(enable_jobs)
    }
    gha_set_output(output)

if __name__ == "__main__":
    args = {}
    args["base_ref"] = os.environ.get("BASE_REF", "HEAD^1")
    main(args)