#!/usr/bin/env bash
###
### fmt — find changed Haskell files and format them with ormolu
###
### Usage:
###   fmt [-c] [-i]
###
### Options:
###   -i        Format files inplace, will change files!
###   -c        Only check formatting, don't change files
###   -h        Print this message

help() {
    sed -rn 's/^### ?//;T;p' "$0"
}

fmt() {
    command -v ormolu >/dev/null 2>&1 || {
        echo >&2 "error: ormolu not found. run this in niv's nix-shell"
        exit 1
    }

    merge_base=$(git merge-base HEAD origin/master)
    changed_files=$(git diff --name-only $merge_base *.hs)

    for f in ${changed_files[@]}
    do
        echo "checking: $f"
        ormolu --mode $mode $f
        if [[ ! $? -eq 0 ]] && [[ "$mode" == "check" ]]
        # ormolu silently fails. let's print an error message so the user know's
        # what's going on
        then
            echo "need fmt: $f"
        fi
    done
    echo "all files checked for formatting"
}

while getopts "ich" arg; do
    case $arg in
        i)  mode="inplace" fmt
            ;;
        c)  mode="check" fmt
            ;;
        *)  help
            exit
            ;;
    esac
done