# gitstatus zsh plugin
#   https://github.com/xylous/gistatus
#
# Code licensed under the MIT License
#   https://raw.githubusercontent.com/xylous/gitstatus/master/LICENSE
#
# @author xylous <xylous.e@gmail.com>
# @maintainer xylous <xylous.e@gmail.com>

###
# Print a formatted gitstatus prompt to stdout
# Options:  -i  add a whitespace at the end, if the output isn't empty
###
function gitstatus()
{
    is_in_git_repository || return 1

    parse_git_status
    local modified="${STATUS[1]}"
    local staged="${STATUS[2]}"
    local deleted="${STATUS[3]}"
    local untracked="${STATUS[4]}"
    unset STATUS

    git_grab_current_branch
    local branch="${REPLY}"

    git_grab_remote_branch
    local remote="${REPLY}"

    [[ ! -z "$remote" ]] \
        && git_local_remote_diffs "$branch" "$remote" \
        && local commit_diffs="$REPLY"

    git_determine_color ${modified} ${staged} ${deleted} ${untracked}
    local color="${REPLY}"

    (( modified > 0 )) \
        && modified="!${modified} "
    (( staged > 0 )) \
        && staged="+${staged} "
    (( deleted > 0 )) \
        && deleted="-${deleted} "
    (( untracked > 0 )) \
        && untracked="?${untracked} "

    local output="${color}"
            output+=" ${branch} "
            output+="${commit_diffs}"
            output+="${modified}"
            output+="${staged}"
            output+="${deleted}"
            output+="${untracked}"

    local true_output="$(sed 's/[ \t]*$//' <<<"${output}")" # remove trailing whitespace

    if [[ "$1" == "-i" ]]; then
        true_output+=" "
    fi

    true_output+=$'%F{default}'
    echo "${true_output}"

    unset REPLY
}

###
# Check if we're in a git repository
# Arguments:    none
# Returns:      0 if in a git repo, 1 otherwise
###
function is_in_git_repository()
{
    git rev-parse --git-dir &>/dev/null || return 1
}

###
# Return current branch we're on
# Arguments:    none
###
function git_grab_current_branch()
{
    typeset -g REPLY="$(git branch --show-current)"
}

###
# Return remote branch that the local one is tracking
# Arguemnts: none
###
function git_grab_remote_branch()
{
    local symbolic_ref="$(git symbolic-ref -q HEAD)"
    typeset -g REPLY="$(git for-each-ref --format='%(upstream:short)' "${symbolic_ref}")"
}

###
# Find how many things have changed since last git commit
# Arguments:    none
###
function parse_git_status()
{
    git status --porcelain=v1 | while IFS= read -r status_line; do
        case "$status_line" in
            ' M '*)
                ((modified++))
                ;;
            'A  '*|'M '*)
                ((staged++))
                ;;
            'D  '*|' D '*)
                ((deleted++))
                ;;
            '?? '*)
                ((untracked++))
                ;;
            'MM '*|'AM '*)
                ((staged++))
                ((modified++))
                ;;
            'R '*)
                ((staged++))
                ((deleted++))
                ;;
        esac
    done

    typeset -g STATUS=("${modified}" "${staged}" "${deleted}" "${untracked}")
    return 0
}

###
# Look at how many commits a local branch is ahead/behind of remote branch
# Arguments:    $1 local branch
#               $2 remote branch
###
function git_local_remote_diffs()
{
    local local_branch="$1"
    local remote_branch="$2"

    local differences="$(git rev-list --left-right --count ${local_branch}...${remote_branch})"
    local commits_ahead=$(echo -n "${differences}" | awk '{print $1}')
    local commits_behind=$(echo -n "${differences}" | awk '{print $2}')
    local ahead="" behind=""

    local result=""

    (( $commits_ahead > 0 )) \
        && ahead="↑${commits_ahead}"
    (( $commits_behind > 0 )) \
        && behind="↓${commits_behind}"

    if [[ ! -z "${ahead}" ]]; then
        result="${ahead} "
    fi

    if [[ ! -z "${behind}" ]]; then
        result="${behind} "
    fi

    typeset -g REPLY="${result}"
}

###
# If there is anything that changed from the past commit, return yellow.
# Otherwise, green.
# Arguments:    list of how many things changed
###
function git_determine_color()
{
    for i in "$@"; do
        if (( $i > 0 )); then
            typeset -g REPLY=$'%F{yellow}'
            return 0
        fi
    done
    typeset -g REPLY=$'%F{green}'
    return 0
}