#!/bin/bash
set -e

RE="https://github.com/([^/?#]+)/([^/?#]+)(/tree/(.+))?"
if [[ "$1" =~ $RE ]]; then
    USER="${BASH_REMATCH[1]}"
    REPO="${BASH_REMATCH[2]}"
    BRANCH="${BASH_REMATCH[4]:-master}"

else
    echo "invalid github repository identifier: '$1'"
    exit 1

fi


call() { echo "$@"; "$@"; echo; }

# {x,,} transforms value to lowercase
case "${2,,}" in

""|"f"|"fetch")
    call git remote add "$USER" git@github.com:"$USER"/"$REPO".git || true
    call git fetch "$USER" "$BRANCH"
    call git checkout -b "$USER-$BRANCH" "$USER/$BRANCH"
    ;;

"m"|"merge")
    RE='\s*(.+)\s+#([0-9]+)'
    if [[ "$3" =~ $RE ]]; then
        TITLE="${BASH_REMATCH[1]}"
        PULL="${BASH_REMATCH[2]}"
    fi

    call git switch master
    call git merge --no-ff --edit -m "merge #${PULL-_}: ${TITLE-_}" "$USER-$BRANCH"
    call git branch -d "$USER-$BRANCH"
    ;;

"p"|"push")
    call git push "$USER" HEAD:"$BRANCH"
    ;;

"pf"|"push-force")
    call git push --force "$USER" HEAD:"$BRANCH"
    ;;

"d"|"delete")
    call git switch master
    call git branch -D "$USER-$BRANCH"
    call git remote remove "$USER"
    ;;

*)
    echo "invalid action: '$2'"
    exit 2
    ;;

esac