#!/usr/bin/env bash
set -e

scriptName=update-source-version # do not use the .wrapped name

die() {
    echo "$scriptName: error: $1" >&2
    exit 1
}

usage() {
    echo "Usage: $scriptName <attr> <version> [<new-source-hash>] [<new-source-url>]"
    echo "                              [--version-key=<version-key>] [--system=<system>] [--file=<file-to-update>] [--rev=<revision>]"
    echo "                              [--ignore-same-hash] [--print-changes]"
}

args=()

for arg in "$@"; do
    case $arg in
        --system=*)
            systemArg="--system ${arg#*=}"
        ;;
        --version-key=*)
            versionKey="${arg#*=}"
        ;;
        --file=*)
            nixFile="${arg#*=}"
            if [[ ! -f "$nixFile" ]]; then
                die "Could not find provided file $nixFile"
            fi
        ;;
        --rev=*)
            newRevision="${arg#*=}"
        ;;
        --ignore-same-hash)
            ignoreSameHash="true"
        ;;
        --print-changes)
            printChanges="true"
        ;;
        --help)
            usage
            exit 0
        ;;
        --*)
            echo "$scriptName: Unknown argument: $arg"
            usage
            exit 1
        ;;
        *)
            args["${#args[*]}"]=$arg
        ;;
    esac
done

attr=${args[0]}
newVersion=${args[1]}
newHash=${args[2]}
newUrl=${args[3]}

# Third-party repositories might not accept arguments in their default.nix.
importTree="(let tree = import ./.; in if builtins.isFunction tree then tree {} else tree)"

if (( "${#args[*]}" < 2 )); then
    echo "$scriptName: Too few arguments"
    usage
    exit 1
fi

if (( "${#args[*]}" > 4 )); then
    echo "$scriptName: Too many arguments"
    usage
    exit 1
fi

if [[ -z "$versionKey" ]]; then
    versionKey=version
fi

if [[ -z "$nixFile" ]]; then
    nixFile=$(nix-instantiate $systemArg --eval --strict -A "$attr.meta.position" | sed -re 's/^"(.*):[0-9]+"$/\1/')
    if [[ ! -f "$nixFile" ]]; then
        die "Couldn't evaluate '$attr.meta.position' to locate the .nix file!"
    fi

    # flake-compat will return paths in the Nix store, we need to correct for that.
    possiblyOutPath=$(nix-instantiate $systemArg --eval -E "with $importTree; outPath" | tr -d '"')
    if [[ -n "$possiblyOutPath" ]]; then
        outPathEscaped=$(echo "$possiblyOutPath" | sed 's#[$^*\\.[|]#\\&#g')
        pwdEscaped=$(echo "$PWD" | sed 's#[$^*\\.[|]#\\&#g')
        nixFile=$(echo "$nixFile" | sed "s|^$outPathEscaped|$pwdEscaped|")
    fi
fi

oldHashAlgo=$(nix-instantiate $systemArg --eval --strict -A "$attr.src.drvAttrs.outputHashAlgo" | tr -d '"')
oldHash=$(nix-instantiate $systemArg --eval --strict -A "$attr.src.drvAttrs.outputHash" | tr -d '"')

if [[ -z "$oldHashAlgo" || -z "$oldHash" ]]; then
    die "Couldn't evaluate old source hash from '$attr.src'!"
fi

if [[ $(grep --count "$oldHash" "$nixFile") != 1 ]]; then
    die "Couldn't locate old source hash '$oldHash' (or it appeared more than once) in '$nixFile'!"
fi

oldUrl=$(nix-instantiate $systemArg --eval -E "with $importTree; builtins.elemAt ($attr.src.drvAttrs.urls or [ $attr.src.url ]) 0" | tr -d '"')

if [[ -z "$oldUrl" ]]; then
    die "Couldn't evaluate source url from '$attr.src'!"
fi

oldVersion=$(nix-instantiate $systemArg --eval -E "with $importTree; $attr.${versionKey} or (builtins.parseDrvName $attr.name).version" | tr -d '"')

if [[ -z "$oldVersion" ]]; then
    die "Couldn't find out the old version of '$attr'!"
fi

if [[ "$oldVersion" = "$newVersion" ]]; then
    echo "$scriptName: New version same as old version, nothing to do." >&2
    if [ -n "$printChanges" ]; then
        printf '[]\n'
    fi
    exit 0
fi

if [[ -n "$newRevision" ]]; then
    oldRevision=$(nix-instantiate $systemArg --eval -E "with $importTree; $attr.src.rev" | tr -d '"')
    if [[ -z "$oldRevision" ]]; then
        die "Couldn't evaluate source revision from '$attr.src'!"
    fi
fi

# Escape regex metacharacter that are allowed in store path names
oldVersionEscaped=$(echo "$oldVersion" | sed -re 's|[.+]|\\&|g')
oldUrlEscaped=$(echo "$oldUrl" | sed -re 's|[${}.+]|\\&|g')

if [[ $(grep --count --extended-regexp "^\s*(let\b)?\s*$versionKey\s*=\s*\"$oldVersionEscaped\"" "$nixFile") = 1 ]]; then
    pattern="/\b$versionKey\b\s*=/ s|\"$oldVersionEscaped\"|\"$newVersion\"|"
elif [[ $(grep --count --extended-regexp "^\s*(let\b)?\s*name\s*=\s*\"[^\"]+-$oldVersionEscaped\"" "$nixFile") = 1 ]]; then
    pattern="/\bname\b\s*=/ s|-$oldVersionEscaped\"|-$newVersion\"|"
else
    die "Couldn't figure out where out where to patch in new version in '$attr'!"
fi

if [[ "$oldHash" =~ ^(sha256|sha512)[:-] ]]; then
    # Handle the possible SRI-style hash attribute (in the form ${type}${separator}${hash})
    # True SRI uses dash as a separator and only supports base64, whereas Nix’s SRI-style format uses a colon and supports all the same encodings like regular hashes (16/32/64).
    # To keep this program reasonably simple, we will upgrade Nix’s format to SRI.
    oldHashAlgo="${BASH_REMATCH[1]}"
    sri=true
elif [[ "$oldHashAlgo" = "null" ]]; then
    # Some fetcher functions support SRI-style `hash` attribute in addition to legacy type-specific attributes. When `hash` is used `outputHashAlgo` is null so let’s complain when SRI-style hash value was not detected.
    die "Unable to figure out hashing scheme from '$oldHash' in '$attr'!"
fi

case "$oldHashAlgo" in
    # Lengths of hex-encoded hashes
    sha256) hashLength=64 ;;
    sha512) hashLength=128 ;;
    *) die "Unhandled hash algorithm '$oldHashAlgo' in '$attr'!" ;;
esac

# Make a temporary all-zeroes hash of $hashLength characters
tempHash=$(printf '%0*d' "$hashLength" 0)

if [[ -n "$sri" ]]; then
    # SRI hashes only support base64
    # SRI hashes need to declare the hash type as part of the hash
    tempHash="$(nix to-sri --type "$oldHashAlgo" "$tempHash")"
fi

# Escape regex metacharacter that are allowed in hashes (+)
oldHashEscaped=$(echo "$oldHash" | sed -re 's|[+]|\\&|g')
tempHashEscaped=$(echo "$tempHash" | sed -re 's|[+]|\\&|g')

# Replace new version
sed -i.bak "$nixFile" -re "$pattern"
if cmp -s "$nixFile" "$nixFile.bak"; then
    die "Failed to replace version '$oldVersion' to '$newVersion' in '$attr'!"
fi

# Replace new URL
if [[ -n "$newUrl" ]]; then
    sed -i "$nixFile" -re "s|\"$oldUrlEscaped\"|\"$newUrl\"|"

    if cmp -s "$nixFile" "$nixFile.bak"; then
        die "Failed to replace source URL '$oldUrl' to '$newUrl' in '$attr'!"
    fi
fi

sed -i "$nixFile" -re "s|\"$oldHashEscaped\"|\"$tempHash\"|"
if cmp -s "$nixFile" "$nixFile.bak"; then
    die "Failed to replace source hash of '$attr' to a temporary hash!"
fi

# Replace new revision, if given
if [[ -n "$newRevision" ]]; then
    sed -i "$nixFile" -re "s|\"$oldRevision\"|\"$newRevision\"|"

    if cmp -s "$nixFile" "$nixFile.bak"; then
        die "Failed to replace source revision '$oldRevision' to '$newRevision' in '$attr'!"
    fi
fi

# If new hash not given on the command line, recalculate it ourselves.
if [[ -z "$newHash" ]]; then
    nix-build $systemArg --no-out-link -A "$attr.src" 2>"$attr.fetchlog" >/dev/null || true
    # FIXME: use nix-build --hash here once https://github.com/NixOS/nix/issues/1172 is fixed
    newHash=$(sed '1,/hash mismatch in fixed-output derivation/d' "$attr.fetchlog" | grep --perl-regexp --only-matching 'got: +.+[:-]\K.+')

    if [[ -n "$sri" ]]; then
        # nix-build preserves the hashing scheme so we can just convert the result to SRI using the old type
        newHash="$(nix to-sri --type "$oldHashAlgo" "$newHash")"
    fi
fi

if [[ -z "$newHash" ]]; then
    cat "$attr.fetchlog" >&2
    die "Couldn't figure out new hash of '$attr.src'!"
fi

if [[ -z "${ignoreSameHash}" && "$oldVersion" != "$newVersion" && "$oldHash" = "$newHash" ]]; then
    mv "$nixFile.bak" "$nixFile"
    die "Both the old and new source hashes of '$attr.src' were equivalent. Please fix the package's source URL to be dependent on '\${version}'!"
fi

sed -i "$nixFile" -re "s|\"$tempHashEscaped\"|\"$newHash\"|"
if cmp -s "$nixFile" "$nixFile.bak"; then
    die "Failed to replace temporary source hash of '$attr' to the final source hash!"
fi

rm -f "$nixFile.bak"
rm -f "$attr.fetchlog"

if [ -n "$printChanges" ]; then
    printf '[{"attrPath":"%s","oldVersion":"%s","newVersion":"%s","files":["%s"]}]\n' "$attr" "$oldVersion" "$newVersion" "$nixFile"
fi