#!/usr/bin/env python3
"""Write a dependency recipe of a Cargo workspace (backlog F6b2).

The recipe is the workspace with its sources stubbed out: every member's
Cargo.toml (and the workspace roots its path dependencies inherit from),
the lock file, real build scripts, and an empty file for each other
target. A third-party crate patched in from vendor/ is copied whole:
registry crates with real code depend on it. Building it compiles exactly the dependencies the real
workspace uses, with the same features, so the build image can hold them
prebuilt: jobs copy that target directory in and compile only their own
crates.

    recipe.py WORKSPACE OUT
"""

import json
import os
import shutil
import subprocess
import sys


def main():
    ws, out = os.path.abspath(sys.argv[1]), os.path.abspath(sys.argv[2])
    meta = json.loads(
        subprocess.run(
            ["cargo", "metadata", "--format-version", "1", "--locked", "--manifest-path", os.path.join(ws, "Cargo.toml")],
            check=True,
            capture_output=True,
        ).stdout
    )
    root = meta["workspace_root"]
    if os.path.exists(out):
        shutil.rmtree(out)

    def put(path, data=None):
        rel = os.path.relpath(path, root)
        if rel.startswith(".."):
            sys.exit(f"{path} is outside the workspace; a recipe holds only paths under it")
        dest = os.path.join(out, rel)
        os.makedirs(os.path.dirname(dest), exist_ok=True)
        if data is None:
            shutil.copy2(path, dest)
        else:
            with open(dest, "w") as f:
                f.write(data)

    for name in ("Cargo.toml", "Cargo.lock"):
        put(os.path.join(root, name))
    members = set(meta["workspace_members"])
    for p in meta["packages"]:
        if p["source"] is not None:
            continue
        manifest = p["manifest_path"]
        src_dir = os.path.dirname(manifest)
        rel = os.path.relpath(src_dir, root)
        if p["id"] not in members and "vendor" in rel.split(os.sep):
            # A third-party crate patched in from a vendor/ directory (the
            # workspace's own, or a pinned subrepo's, as oxygenhub patches
            # from deps/…/oxygen/vendor/): registry crates
            # with real code depend on it, so it goes in whole. (A pinned
            # subrepo's crates under deps/ are stubbed like the members:
            # only stubbed code depends on them.)
            shutil.copytree(src_dir, os.path.join(out, rel), dirs_exist_ok=True)
            continue
        put(manifest)
        # Workspace roots above a path dependency, for `workspace = true`.
        d = os.path.dirname(os.path.dirname(manifest))
        while d.startswith(root) and d != root:
            top = os.path.join(d, "Cargo.toml")
            if os.path.exists(top):
                put(top)
            d = os.path.dirname(d)
        for t in p["targets"]:
            kind = t["kind"][0]
            src = t["src_path"]
            if kind == "custom-build":
                put(src)
            elif kind in ("lib", "rlib", "proc-macro"):
                put(src, "")
            else:
                put(src, "fn main() {}\n")


if __name__ == "__main__":
    main()