#!/usr/bin/env bash
# Format staged source files with the standard formatter for each language.
set -euo pipefail

root=$(git rev-parse --show-toplevel)
cd "$root"

# Read staged paths safely, including paths containing whitespace.
mapfile -d '' files < <(git diff --cached --name-only --diff-filter=ACMR -z)
((${#files[@]})) || exit 0

format() {
    local tool=$1
    shift
    command -v "$tool" >/dev/null 2>&1 || {
        printf 'format: required formatter not found: %s\n' "$tool" >&2
        exit 1
    }
    "$tool" "$@"
}

java=() c=() cpp=() go=() python=() js=() web=()
for file in "${files[@]}"; do
    case "$file" in
        *.java) java+=("$file") ;;
        *.c|*.h) c+=("$file") ;;
        *.cc|*.cpp|*.cxx|*.hpp|*.hh|*.hxx) cpp+=("$file") ;;
        *.go) go+=("$file") ;;
        *.py) python+=("$file") ;;
        *.js|*.jsx|*.ts|*.tsx|*.json|*.css|*.html|*.md|*.yaml|*.yml) web+=("$file") ;;
    esac
done

((${#java[@]} == 0)) || format google-java-format --replace "${java[@]}"
((${#c[@]} == 0)) || format clang-format -i "${c[@]}"
((${#cpp[@]} == 0)) || format clang-format -i "${cpp[@]}"
((${#go[@]} == 0)) || format gofmt -w "${go[@]}"
((${#python[@]} == 0)) || format black "${python[@]}"
((${#web[@]} == 0)) || format prettier --write "${web[@]}"

# Include formatter output in the commit; never silently leave unstaged formatting.
git add -- "${files[@]}"