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

url=$1
rev=$2
expHash=$3

hashType=${NIX_HASH_ALGO:-sha256}
if test -z "${hashFormat:-}"; then
    hashFormat=--sri
fi

if test -z "$url"; then
    echo "syntax: nix-prefetch-bzr URL [REVISION [EXPECTED-HASH]]" >&2
    exit 1
fi

revarg="-r $rev"
test -n "$rev" || revarg=""

repoName=$(echo $url | sed '
  s,.*/\([^/]\+\)/trunk/*$,\1,;t
  s,.*/\([^/]\+\)/branches/\([^/]\+\)/*$,\1-\2,;t
  s,.*/\([^/]\+\)/tags/\([^/]\+\)/*$,\1-\2,;t
  s,.*/\([^/]\+\)/*$,\1,;t
')
dstFile="bzr-export"

# 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" $dstFile)
    if ! nix-store --check-validity "$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 "$finalPath"; then
    # nix>=2.20 rejects adding symlinked paths to the store, so use realpath
    # to resolve to a physical path. https://github.com/NixOS/nix/issues/11941
    tmpPath="$(realpath "$(mktemp -d --tmpdir bzr-checkout-tmp-XXXXXXXX)")"
    trap "rm -rf \"$tmpPath\"" EXIT

    tmpFile="$tmpPath/$dstFile"

    # Perform the checkout.
    bzr -Ossl.cert_reqs=none export $revarg --format=dir "$tmpFile" "$url"

    echo "bzr revision is $(bzr revno $revarg "$url")"

    # 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" != "$hash"; then
        echo "hash mismatch for URL \`$url'"
        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
