#!/usr/bin/env python
import argparse
import glob
import subprocess
from pathlib import Path

import yaml


def flatten(d, path):
    """
    Flatten a dictionary into ('some/path/to/key', value)

    >>> flatten({'a': {'b': 2}, 'q': 3}, [])
    [('a.b', 2), ('q', 3)]
    """

    if isinstance(d, dict):
        for k, v in d.items():
            yield from flatten(v, path + [k])
    else:
        yield (".".join(path), d)


def flat_dict(d):
    return dict(flatten(d, []))


# Load without the includes since we can't follow those across git revisions.
class MockOrderedLoader(yaml.SafeLoader):
    def METHOD_NAME(self, node):
        return {}


MockOrderedLoader.add_constructor("!include", MockOrderedLoader.METHOD_NAME)


def diff_files(old, new):
    # Flatten them
    old_kv = flat_dict(old)
    new_kv = flat_dict(new)

    # Compare them
    old_k = set(old_kv.keys())
    new_k = set(new_kv.keys())

    added = []
    for item in new_k - old_k:
        parent = ".".join(item.split(".")[0:-1])
        if parent in new_k and parent not in old_k:
            added.append(item)
        else:
            added.append(parent)
    added = set(added)

    removed = []
    for item in old_k - new_k:
        parent = ".".join(item.split(".")[0:-1])
        if parent in old_k and parent not in new_k:
            removed.append(item)
        else:
            removed.append(parent)
    removed = set(removed)

    shared = old_k & new_k
    changed = [(k, old_kv[k], new_kv[k]) for k in shared if old_kv[k] != new_kv[k]]

    return added, removed, changed


def _report_dict(title, subheading, data, mapper):
    print(title)
    print("-" * len(title))
    print()
    print(subheading)
    print()
    for fn in data:
        print(fn)
        print("~" * len(fn))
        print()
        for k in data[fn]:
            print(mapper(k))
        print()
    print()


def _indent(s, by=4):
    whitespace = " " * by
    s = s if isinstance(s, list) else str(s).splitlines()
    return "\n".join(f"{whitespace}{line}" for line in s)


def report_diff(added, changed, removed, new_files):
    # Print out report
    if added or changed or removed:
        print("Configuration Changes")
        print("=====================")
        print()

    if added:
        _report_dict("Added", "The following configuration options are new", added, lambda x: f"-  {x}")

    if changed:
        _report_dict(
            "Changed",
            "The following configuration options have been changed",
            changed,
            lambda x: f"-  {x[0]} has changed from\n\n   ::\n\n{_indent(x[1])}\n\n   to\n\n   ::\n\n{_indent(x[2])}\n\n",
        )

    if removed:
        _report_dict(
            "Removed", "The following configuration options have been completely removed", removed, lambda x: f"-  {x}"
        )

    if new_files:
        print("New Configuration Files")
        print("-----------------------")
        print()
        print("The following files are new, or recently converted to yaml")
        print()
        for k in new_files:
            print(f"-  ``{k}``")


def load_at_time(path, revision=None):
    if revision is not None:
        return subprocess.check_output(["git", "show", f"{revision}:{path}"], stderr=subprocess.STDOUT)
    else:
        with open(path) as handle:
            return handle.read()


def main(old_revision, new_revision=None):
    globs = (
        "config/*.yml.sample",
        "lib/galaxy/config/schemas/*schema.yml",
    )
    files_to_diff = [f for g in globs for f in glob.glob(g)]
    added = {}
    removed = {}
    changed = {}
    new_files = []

    for file in files_to_diff:
        filename = file
        if "config_schema.yml" in file:
            filename = "config/galaxy.yml.sample:galaxy"

        real_path = Path(file).resolve().relative_to(Path.cwd())
        try:
            old_contents = yaml.load(load_at_time(real_path, old_revision), Loader=MockOrderedLoader)
            new_contents = yaml.load(load_at_time(real_path, new_revision), Loader=MockOrderedLoader)

            (a, r, c) = diff_files(old_contents, new_contents)
            if a:
                added[filename] = sorted(a)

            if r:
                removed[filename] = sorted(r)

            if c:
                changed[filename] = sorted(c)

        except subprocess.CalledProcessError:
            new_files.append(file)

    report_diff(added, changed, removed, new_files)


if __name__ == "__main__":
    parser = argparse.ArgumentParser(description="Diff yaml configuration files between two points in time.")
    parser.add_argument("old_revision", help="Old revision")
    parser.add_argument(
        "--new_revision",
        help="New revision (defaults to whatever is currently in tree)",
    )
    args = parser.parse_args()
    main(args.old_revision, args.new_revision)