#!/usr/bin/env python3
# Copyright 2020 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.
"""
A hacky script to clean up recipe DEPS:
- Delete unused recipe and recipe module DEPS. It uses a simple heuristic for
  this, which may produce some false positives and false negatives.
  OPTIONAL_TODO: Using the ast module would be a more reliable way of
  detecting dep uses, since this heuristic might find usages in docstrings
  and trailing comments.
- Ensure all deps are prefixed with a repo name (e.g. "fuchsia").
- Sort all DEPS lists alphabetically.
"""

import argparse
import difflib
import functools
import json
import os
import re
import sys


def main():
    parser = argparse.ArgumentParser(description="Sort and filter recipe DEPS")
    parser.add_argument(
        "--check",
        action="store_true",
        help=(
            "Instead of writing changes, print diff to stdout and exit with retcode 1 "
            "if cleanup is needed."
        ),
    )
    parser.add_argument(
        "--json-output",
        type=str,
        help=(
            "Write a JSON list of relative paths of badly formatted files to this file."
        ),
    )
    args = parser.parse_args()

    cwd = os.getcwd()

    # Get the name of this recipes repo to append to any DEPS that don't
    # specify a repo.
    with open(os.path.join(cwd, "infra", "config", "recipes.cfg")) as f:
        cfg = json.load(f)
    repo_name = cfg["repo_name"]

    files_with_deps = []

    recipes_dir = os.path.join(cwd, "recipes")
    modules_dir = os.path.join(cwd, "recipe_modules")
    for directory in [recipes_dir, modules_dir]:
        for subdir, _, files in os.walk(directory):
            for relpath in files:
                _, ext = os.path.splitext(relpath)
                if ext != ".py":
                    continue
                path = os.path.join(subdir, relpath)
                # __init__.py files are handled separately, since they contain
                # DEPS entries but usages of those deps may be in other files
                # in the directory.
                if relpath == "__init__.py":
                    continue
                files_with_deps.append(analyze_recipe(path, repo_name))

    for relpath in os.listdir(modules_dir):
        path = os.path.join(modules_dir, relpath)
        if os.path.exists(os.path.join(path, "api.py")):
            files_with_deps.append(analyze_module(path, repo_name))

    files_to_fix = [f for f in files_with_deps if f.diff]
    for f in files_to_fix:
        if args.check:
            script_relpath = os.path.relpath(__file__, cwd)
            print(
                "Some recipe files' DEPS are malformatted.\n"
                "Run ./%s to fix:\n" % script_relpath
            )
            print(f.diff)
        else:
            f.rewrite()

    if args.json_output:
        with open(args.json_output, "w") as outfile:
            json.dump([os.path.relpath(f.path, cwd) for f in files_to_fix], outfile)

    if args.check and files_to_fix:
        sys.exit(1)


class FileWithDEPS(object):
    def __init__(self, path, repo_name):
        """Read the file and its DEPS."""
        self.path = path
        self._repo_name = repo_name

        # To be updated by the caller after static analysis.
        self.used_deps = set()

        # A mapping from full dep name (e.g. "fuchsia/foo") to a list of lines
        # that correspond to that dep - the actual import line that names the
        # dep, along with any comments preceding the import line. All lines
        # include any trailing newline.
        self.original_deps = {}
        # The original lines of the file, including trailing newlines.
        self.original_lines = []

        # The line number of the first dep.
        self._deps_start_line = -1
        # The line number of the line after the last dep.
        self._deps_end_line = -1

        with open(self.path) as f:
            self.original_lines = f.readlines()

        # The lines associated with the dep currently being parsed, including any
        # comment lines preceding the dep.
        current_dep_lines = []

        for i, original_line in enumerate(self.original_lines):
            line = original_line.strip()
            if line == "DEPS = [":
                self._deps_start_line = i + 1
                continue
            elif self._deps_start_line == -1:
                continue
            elif line == "]":
                self._deps_end_line = i
                break

            if line.startswith("#"):
                current_dep_lines.append(original_line)
                continue

            match = re.search(r'([\'|"])(?P<dep>\S+)\1,?\s*(?P<comment>\#.*)?$', line)
            if not match:
                current_dep_lines.append(original_line)
                continue

            dep = match.group("dep")

            dep_line = original_line
            # Prepend the recipe repo name (assumed to be repo_name) if it's
            # missing.
            if "/" not in dep:
                old_dep = dep
                dep = "%s/%s" % (self._repo_name, old_dep)
                dep_line = dep_line.replace(old_dep, dep, 1)

            current_dep_lines.append(dep_line)
            self.original_deps[dep] = "".join(current_dep_lines)
            current_dep_lines = []

    @property
    @functools.lru_cache
    def new_lines(self):
        """Returns a list of the lines of the file with formatting applied."""
        new_deps = {}
        for dep, lines in self.original_deps.items():
            dep_basename = dep.split("/")[-1]
            if dep in self.used_deps or dep_basename in self.used_deps:
                new_deps[dep] = lines

        sorted_dep_lines = [text for _, text in sorted(new_deps.items())]
        new_lines = self.original_lines[:]
        new_lines[self._deps_start_line : self._deps_end_line] = sorted_dep_lines
        return new_lines

    @property
    @functools.lru_cache
    def diff(self):
        """Returns a git-style rendering of the diff that would be produced."""
        return "".join(
            difflib.unified_diff(
                self.original_lines, self.new_lines, "a" + self.path, "b" + self.path
            )
        ).rstrip()

    def rewrite(self):
        print("rewriting %s" % os.path.relpath(self.path, os.getcwd()))
        with open(self.path, "w") as f:
            f.writelines(self.new_lines)


def analyze_recipe(path, repo_name):
    """Check for unused DEPS in a recipe file.

    Args:
        path (str): The absolute path to the recipe Python file.
        repo_name (str): The name of the current recipes repo.
    """
    recipe_file = FileWithDEPS(path, repo_name)
    for dep in recipe_file.original_deps:
        # This is a simple heuristic: for a dep "foo", consider it used if
        # "api.foo" is found anywhere in the file.
        dep_regex = re.compile(r"api\.{}\b".format(dep.split("/")[-1]))
        for line in recipe_file.original_lines:
            if line.strip().startswith("#"):
                continue
            if dep_regex.search(line):
                recipe_file.used_deps.add(dep)
                break

    return recipe_file


def analyze_module(module_dir, repo_name):
    """Check for unused DEPS in a recipe module's __init__.py file.

    Args:
        module_dir (str): The absolute path to the root of the recipe module.
        repo_name (str): The name of the current recipes repo.
    """
    # We'll search for matches of this regex in each of this module's files as
    # a heuristic for determining which dependencies the module uses.
    usage_regex = re.compile(r"\b((self\.)?\b_?api|self\.m)\.(?P<dep>\w+)\b")
    init_path = os.path.join(module_dir, "__init__.py")
    if not os.path.exists(init_path):
        raise Exception(
            "recipe module %s has no __init__.py file" % (os.path.dirname(module_dir))
        )
    init_file = FileWithDEPS(init_path, repo_name)
    for subdir, subdirs, files in os.walk(module_dir, topdown=True):
        # The "examples" directory contains standalone recipes that don't
        # relate to the recipe module's DEPS and shouldn't be taken into
        # account when computing the recipe module's unused DEPS. Likewise, the
        # "resources" directory contains standalone scripts that don't use
        # recipe DEPS at all.
        if subdir == module_dir:
            for special_subdir in ["examples", "resources"]:
                if special_subdir in subdirs:
                    # Tell os.walk() not to enter this subdirectory.
                    subdirs.remove(special_subdir)

        for relpath in files:
            _, ext = os.path.splitext(relpath)
            if ext != ".py":
                continue
            path = os.path.join(subdir, relpath)

            with open(path) as f:
                lines = f.readlines()
            for line in lines:
                if line.strip().startswith("#"):
                    continue
                for match in usage_regex.finditer(line):
                    init_file.used_deps.add(match.group("dep"))

    return init_file


if __name__ == "__main__":
    main()