"""Diff dependency manifests to produce PackageDiff."""
from __future__ import annotations

import json
import re

from scripts.manifest import PackageDiff, PackageEntry, PackageUpgrade


_REQ_LINE_RE = re.compile(
    r"^\s*(?P<name>[A-Za-z0-9_\-.]+)\s*==\s*(?P<version>[^\s#]+)"
)


def _parse_requirements(text: str) -> dict[str, str]:
    out: dict[str, str] = {}
    for line in text.splitlines():
        line = line.split("#", 1)[0]
        m = _REQ_LINE_RE.match(line)
        if m:
            out[m.group("name").lower()] = m.group("version")
    return out


def _diff_maps(before: dict[str, str], after: dict[str, str]) -> PackageDiff:
    added = [
        PackageEntry(name=n, version=v)
        for n, v in sorted(after.items()) if n not in before
    ]
    removed = [
        PackageEntry(name=n, version=v)
        for n, v in sorted(before.items()) if n not in after
    ]
    upgraded = [
        PackageUpgrade(name=n, from_version=before[n], to_version=after[n])
        for n in sorted(before.keys() & after.keys())
        if before[n] != after[n]
    ]
    return PackageDiff(added=added, removed=removed, upgraded=upgraded)


def diff_requirements_txt(before: str, after: str) -> PackageDiff:
    return _diff_maps(_parse_requirements(before), _parse_requirements(after))


def _parse_package_json(text: str) -> dict[str, str]:
    try:
        doc = json.loads(text)
    except json.JSONDecodeError:
        return {}
    out: dict[str, str] = {}
    for key in ("dependencies", "devDependencies"):
        section = doc.get(key) or {}
        if isinstance(section, dict):
            for name, version in section.items():
                if isinstance(version, str):
                    out[name.lower()] = version
    return out


def diff_package_json(before: str, after: str) -> PackageDiff:
    return _diff_maps(_parse_package_json(before), _parse_package_json(after))