#!/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 local
package'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. 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))
    for p in meta["packages"]:
        if p["source"] is not None:
            continue
        manifest = p["manifest_path"]
        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()