#!/usr/bin/env python3
"""
Diff workspace dependencies between two git revisions.

Compares both Cargo.toml [workspace.dependencies] and Cargo.lock [[package]]
entries to find which dependencies have changed.

Usage: diff-cargo-deps <old-git-ref>

Outputs one dependency name per line for any deps that were added, removed,
or modified (version, features, checksum, etc).
"""

import subprocess
import sys
import tomllib


def get_file_at_ref(ref: str, path: str) -> str:
    """Get file contents at a specific git ref."""
    result = subprocess.run(
        ["git", "show", f"{ref}:{path}"],
        capture_output=True,
        text=True,
    )
    return result.stdout if result.returncode == 0 else ""


def get_workspace_deps(toml_content: str) -> dict:
    """Extract [workspace.dependencies] from Cargo.toml content."""
    if not toml_content:
        return {}
    try:
        data = tomllib.loads(toml_content)
        return data.get("workspace", {}).get("dependencies", {})
    except Exception:
        return {}


def get_lock_packages(lock_content: str) -> dict[str, dict]:
    """Extract [[package]] entries from Cargo.lock as {name: full_entry}."""
    if not lock_content:
        return {}
    try:
        data = tomllib.loads(lock_content)
        return {pkg["name"]: pkg for pkg in data.get("package", [])}
    except Exception:
        return {}


def diff_dicts(old: dict, new: dict) -> set[str]:
    """Find keys that were added, removed, or whose values changed."""
    changed = set()

    for name, value in new.items():
        if name not in old or old[name] != value:
            changed.add(name)

    for name in old:
        if name not in new:
            changed.add(name)

    return changed


def main():
    if len(sys.argv) < 2:
        print("Usage: diff-cargo-deps <old-git-ref>", file=sys.stderr)
        sys.exit(1)

    old_ref = sys.argv[1]
    changed = set()

    # Diff Cargo.toml workspace dependencies
    old_toml = get_file_at_ref(old_ref, "Cargo.toml")
    new_toml = open("Cargo.toml").read()
    old_deps = get_workspace_deps(old_toml)
    new_deps = get_workspace_deps(new_toml)
    changed |= diff_dicts(old_deps, new_deps)

    # Diff Cargo.lock packages
    old_lock = get_file_at_ref(old_ref, "Cargo.lock")
    new_lock = open("Cargo.lock").read()
    old_pkgs = get_lock_packages(old_lock)
    new_pkgs = get_lock_packages(new_lock)
    changed |= diff_dicts(old_pkgs, new_pkgs)

    for name in sorted(changed):
        print(name)


if __name__ == "__main__":
    main()