.bash_prompt

#!/bin/bash

# The various escape codes that we can use to color our prompt.
RED="\[\033[0;31m\]"
YELLOW="\[\033[1;33m\]"
GREEN="\[\033[0;32m\]"
BLUE="\[\033[1;34m\]"
LIGHT_RED="\[\033[1;31m\]"
LIGHT_GREEN="\[\033[1;32m\]"
WHITE="\[\033[1;37m\]"
LIGHT_GRAY="\[\033[1;30m\]"
COLOR_OCHRE="\[\033[38;5;95m\]"
COLOR_NONE="\[\e[0m\]"

# Detect whether the current directory is a git repository.
function is_git_repository {
    git branch > /dev/null 2>&1
}

# Determine the branch/state information for this git repository.
function set_git_branch {
    # Capture the output of the "git status" command.
    git_status="$(git status 2> /dev/null)"

    # Set color based on clean/staged/dirty.
    if [[ ${git_status} =~ "nothing to commit, working directory clean" ]]; then
        state="${GREEN}"
    elif [[ ${git_status} =~ "Changes to be committed:" ]]; then
        state="${YELLOW}"
    elif [[ ${git_status} =~ "Changes not staged for commit:" ]]; then
        state="${LIGHT_RED}"
    elif [[ ${git_status} =~ "Untracked files:" ]]; then
        state="${BLUE}"
    else
        state="${COLOR_OCHRE}"
    fi

    # Set arrow icon based on status against remote.
    remote_pattern="Your branch is (.*) of"
    if [[ ${git_status} =~ ${remote_pattern} ]]; then
        if [[ ${BASH_REMATCH[1]} == "ahead" ]]; then
            remote="^"
        else
            remote="v"
        fi
    else
        remote=""
    fi
    diverge_pattern="Your branch and (.*) have diverged"
    if [[ ${git_status} =~ ${diverge_pattern} ]]; then
        remote="^v"
    fi

    # Get the name of the branch.
    branch_pattern="On branch ([^${IFS}]*)"
    if [[ ${git_status} =~ ${branch_pattern} ]]; then
        branch=${BASH_REMATCH[1]}
    fi

    # Set the final branch string.
    BRANCH="${state}(${branch})${remote}${COLOR_NONE} "
}

# Return the prompt symbol to use, colorized based on the return value of the
# previous command.
function set_prompt_symbol () {
    if test $1 -eq 0 ; then
        PROMPT_SYMBOL="${COLOR_NONE}\$${COLOR_NONE}"
    else
        PROMPT_SYMBOL="${LIGHT_RED}\$${COLOR_NONE}"
    fi
}

# Determine active yroot env
function set_yroot () {
    if [ "x$YROOT_NAME" != "x" ]; then
        YROOT_PROMPT="${GREEN}as ${COLOR_NONE}${YROOT_NAME}"
    else
        YROOT_PROMPT=""
    fi
}

# Set the full bash prompt.
function set_bash_prompt () {
    # Set the PROMPT_SYMBOL variable. We do this first so we don't lose the
    # return value of the last command.
    set_prompt_symbol $?

    # Set the PYTHON_VIRTUALENV variable.
    set_yroot

    # Set the BRANCH variable.
    if is_git_repository ; then
        set_git_branch
    else
        BRANCH=''
    fi

    # Set the bash prompt variable.
    PS1="
${COLOR_NONE}\u@\h ${GREEN}in${COLOR_NONE} \w${COLOR_NONE} ${YROOT_PROMPT} ${BRANCH}
${PROMPT_SYMBOL} "
}

# Tell bash to execute this function just before displaying its prompt.
PROMPT_COMMAND=set_bash_prompt