#!/bin/sh
# rustc from a pinned upstream tarball (scripts/rustc.dotslash).
#
# The Rust dist tarball keeps its components in sibling directories, so the
# compiler's default sysroot (rustc/) holds no libstd — it lives under
# rust-std-<triple>/. Point --sysroot at that sibling; the compiler's own
# codegen libraries are still found via rpath, relative to the binary.
set -e
dir=$(CDPATH= cd -- "$(dirname -- "$0")" && pwd)
exe=$(dotslash -- fetch "$dir/rustc.dotslash")

# Callers that set their own sysroot win — buck2's rustc_cfg action passes an
# empty --sysroot, and rustc rejects the option being given twice.
for arg in "$@"; do
    case $arg in
        --sysroot|--sysroot=*) exec "$exe" "$@" ;;
    esac
done

root=$(dirname -- "$(dirname -- "$(dirname -- "$exe")")")
host_std=
for std in "$root"/rust-std-*/; do
    host_std=${std%/}
    break
done
[ -n "$host_std" ] || { echo "scripts/rustc: no rust-std component under $root" >&2; exit 1; }

# Cross-compiling needs one sysroot holding both triples: the host's, for proc
# macros and build scripts, and the target's, for the crate being built. The
# components ship as separate tarballs, so stitch them together as a symlink
# farm — cheap to build, and stable enough to cache across invocations.
#
# buck2 passes rustc its arguments in an @argsfile, so --target is usually not
# in argv at all; look inside those too.
scan_target() {
    prev=
    for arg in "$@"; do
        case $arg in
            --target=*-linux-android) echo "${arg#--target=}"; return ;;
            *-linux-android) [ "$prev" = "--target" ] && { echo "$arg"; return; } ;;
            @*) if [ -f "${arg#@}" ]; then
                    found=$(sed -n 's/^"\{0,1\}\(--target=\)\{0,1\}\([a-z0-9_]*-linux-android[0-9]*\)"\{0,1\}$/\2/p' \
                        "${arg#@}" | head -n1)
                    [ -n "$found" ] && { echo "$found"; return; }
                fi ;;
        esac
        prev=$arg
    done
}

android_target=$(scan_target "$@")

if [ -z "$android_target" ]; then
    exec "$exe" --sysroot "$host_std" "$@"
fi

std_install=$(dotslash -- fetch "$dir/rust-std-android.dotslash")
target_std=$(dirname -- "$std_install")/rust-std-$android_target

merged=${XDG_CACHE_HOME:-$HOME/.cache}/vidya-rust-sysroot/$(basename -- "$host_std")+$android_target
if [ ! -d "$merged/lib/rustlib/$android_target" ]; then
    tmp=$merged.$$
    rm -rf -- "$tmp"
    mkdir -p -- "$tmp/lib/rustlib"
    for entry in "$host_std"/lib/*; do
        [ "$(basename -- "$entry")" = rustlib ] && continue
        ln -sfn -- "$entry" "$tmp/lib/"
    done
    for entry in "$host_std"/lib/rustlib/*; do
        ln -sfn -- "$entry" "$tmp/lib/rustlib/"
    done
    ln -sfn -- "$target_std/lib/rustlib/$android_target" "$tmp/lib/rustlib/$android_target"
    rm -rf -- "$merged"
    mv -- "$tmp" "$merged" 2>/dev/null || rm -rf -- "$tmp"
fi

exec "$exe" --sysroot "$merged" "$@"