#!/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()