#!/usr/bin/env fuchsia-vendored-python
# Copyright 2019 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.

import argparse
import difflib
import filecmp
import json
import os
import shutil
import sys

# Verifies that the candidate golden file matches the provided golden.

MANUAL_UPDATE_HEADER = """
Please run the following to acknowledge this change:
```"""

MANUAL_UPDATE_BODY_ENTRY = """fx run-in-build-dir cp \\
    {candidate} \\
    {golden}
"""

MANUAL_UPDATE_FOOTER = """```

Or, you can simply rebuild with `update_goldens=true` set in your GN args.

Note: If you are seeing this on an automated build failure and are trying to
reproduce, ensure that
    {label}
is in your GN graph.
"""


def print_failure_msg(manual_updates, label):
    print(MANUAL_UPDATE_HEADER)
    for update in manual_updates:
        print(
            MANUAL_UPDATE_BODY_ENTRY.format(
                candidate=update["candidate"], golden=update["golden"]
            )
        )
    print(MANUAL_UPDATE_FOOTER.format(label=label))


def get_diff_lines(file1, file2):
    """Returns a list of strings representing the unified diff of the two file."""
    with open(file1) as f:
        lines1 = f.readlines()
    with open(file2) as f:
        lines2 = f.readlines()
    return list(difflib.unified_diff(lines1, lines2, file1, file2))


def main():
    parser = argparse.ArgumentParser()
    parser.add_argument("--label", help="GN label for this test", required=True)
    parser.add_argument(
        "--source-root", help="Path to the Fuchsia source root", required=True
    )
    parser.add_argument(
        "--comparisons",
        metavar="FILE",
        help="Path at which to find the JSON file containing the comparisons",
        required=True,
    )
    parser.add_argument(
        "--depfile", help="Path at which to write the depfile", required=True
    )
    parser.add_argument(
        "--stamp-file",
        help="Path at which to write the stamp file",
        required=True,
    )
    parser.add_argument(
        "--bless",
        help="Overwrites the golden with the candidate if they don't match - or creates it if it does not yet exist",
        action="store_true",
    )
    parser.add_argument(
        "--warn",
        help="Whether API changes should only cause warnings",
        action="store_true",
    )
    parser.add_argument(
        "--err-msg",
        help="Additional error message to display if files don't match",
    )
    parser.add_argument(
        "--binary",
        help="Use binary comparison for the files.",
        action="store_true",
    )
    args = parser.parse_args()

    with open(args.comparisons) as f:
        comparisons = json.load(f)

    inputs = []
    manual_updates = []
    for comparison in comparisons:
        # Unlike the candidate and formatted_golden, which are build directory
        # -relative paths, the golden is source-relative.
        golden = os.path.join(args.source_root, comparison["golden"])
        candidate = comparison["candidate"]
        inputs.extend([candidate, golden])

        # A formatted golden might have been supplied. Compare against that if
        # present. (In the case of a non-existent golden, this file is empty.)
        formatted_golden = comparison.get("formatted_golden")
        if formatted_golden:
            inputs.append(formatted_golden)

        diff_lines = []
        if os.path.exists(golden):
            if args.binary:
                current_comparison_failed = not filecmp.cmp(
                    candidate, formatted_golden or golden
                )
            else:
                diff_lines = get_diff_lines(
                    formatted_golden or golden, candidate
                )
                current_comparison_failed = bool(diff_lines)
        else:
            current_comparison_failed = True

        if current_comparison_failed:
            type = "Warning" if args.warn or args.bless else "Error"
            str = f"\n{type}: "
            if args.err_msg:
                str += args.err_msg
            else:
                str += f'Golden file mismatch: {comparison["golden"]}'

            if diff_lines:
                max_diff_lines = 16
                if len(diff_lines) > max_diff_lines:
                    str += f"\nDiff (-golden +actual, truncated):\n"
                else:
                    str += f"\nDiff (-golden +actual):\n"
                str += "".join(diff_lines[:max_diff_lines])

            print(str)

            if args.bless:
                os.makedirs(os.path.dirname(golden), exist_ok=True)
                shutil.copyfile(candidate, golden)
            else:
                manual_updates.append(dict(golden=golden, candidate=candidate))

    # Print all of the manual update instructions once at the end to reduce the
    # amount of rebuilding and copy-pasting.
    if manual_updates:
        print_failure_msg(manual_updates, args.label)
        if not args.warn:
            return 1

    with open(args.stamp_file, "w") as stamp_file:
        stamp_file.write("Golden!\n")

    with open(args.depfile, "w") as depfile:
        depfile.write("%s: %s\n" % (args.stamp_file, " ".join(inputs)))

    return 0


if __name__ == "__main__":
    sys.exit(main())