#!/usr/bin/env bash
set -euo pipefail

cvsRoot=$1
module=$2
tag=$3
expHash=$4

hashType=${NIX_HASH_ALGO:-sha256}

if test -z "$cvsRoot"; then
    echo "syntax: nix-prefetch-cvs CVSROOT MODULE [TAG [HASH]]" >&2
    exit 1
elif test -z "$module"; then
    echo "syntax: nix-prefetch-cvs CVSROOT MODULE [TAG [HASH]]" >&2
    exit 1
fi


mkTempDir() {
    # nix>=2.20 rejects adding symlinked paths to the store, so use realpath
    # to resolve to a physical path. https://github.com/NixOS/nix/issues/11941
    tmpPath="$(realpath "$(mktemp -d --tmpdir nix-prefetch-csv-XXXXXXXX)")"
    trap removeTempDir EXIT
}

removeTempDir() {
    rm -rf "$tmpPath"
}


# If the hash was given, a file with that hash may already be in the
# store.
if test -n "$expHash"; then
    finalPath=$(nix-store --print-fixed-path --recursive "$hashType" "$expHash" cvs-export)
    if ! nix-store --check-validity "$finalPath" 2> /dev/null; then
        finalPath=
    fi
    hash=$expHash
fi


# If we don't know the hash or a path with that hash doesn't exist,
# download the file and add it to the store.
if test -z "$finalPath"; then

    mkTempDir
    tmpFile=$tmpPath/cvs-export
    #mkdir $tmpPath

    # Perform the checkout.
    if test -z "$tag"; then
        args=(-D "now")
    elif test "${USE_DATE:-}" = "1"; then
        args=(-D "$tag")
    else
        args=(-r "$tag")
    fi
    (cd "$tmpPath" && cvs -f -z0 -d $cvsRoot export "${args[*]}" -d cvs-export $module >&2)

    # Compute the hash.
    hash=$(nix-hash --type $hashType ${hashFormat:-"--sri"} $tmpFile)
    if ! test -n "${QUIET:-}"; then echo "hash is $hash" >&2; fi

    # Add the downloaded file to the Nix store.
    finalPath=$(nix-store --add-fixed --recursive "$hashType" $tmpFile)

    if test -n "$expHash" -a "$expHash" != "$hash"; then
        echo "hash mismatch for CVS root \`$cvsRoot'"
        exit 1
    fi
fi

if ! test -n "${QUIET:-}"; then echo "path is $finalPath" >&2; fi

echo $hash

if test -n "${PRINT_PATH:-}"; then
    echo $finalPath
fi
