#!/bin/sh

# Description:
#   Try hard to identify the current revision of the code.
#   Works for Git and the Github SVN bridge.
#   For a SVN sandbox, requires connection to (and authentication
#   with) the server.
# Usage:
#   pc_identify_revision [--reset|-r] [--print-file-name|-p]
# Examples:
#   pc_identify_revision                    # Write revision file
#   pc_identify_revision --reset            # Delete revision file
#   pc_identify_revision --print-file-name  # print name of rev. file

revision_file='revision.txt'
quiet=''                        # set to '1' to suppress diff output


reset_locale () {
    # Reset the locale to make the output from e.g. 'svn info' predictable.
    # Sometimes LANG is crucial, sometimes only LANGUAGE or LC_ALL are.
    export LANG=POSIX
    export LANGUAGE="${LANG}" LC_ALL="${LANG}"
}


check_prerequisites () {
    # Sanity checks.
    # Some of these requirements could be weakened, but it is better
    # to play safe.
    if [ -z $PENCIL_HOME ]; then
        echo "Error: \$PENCIL_HOME must be set."
        exit 1
    fi
}


write_revision_file () {
    printf 'Revision: ' >> ${revision_file}

    if [ -d "${PENCIL_HOME}/.git" ]; then
        write_revision_file_from_git_sandbox
    elif [ -d "${PENCIL_HOME}/.svn" ]; then
        write_revision_file_from_svn_sandbox
    else
        echo 'Warning: Cannot determine a revision number' \
            >> ${revision_file}
    fi
}


write_revision_file_from_git_sandbox () {
    git_cmd rev-parse HEAD >> ${revision_file}
    git_cmd status --short --untracked-files=no >> ${revision_file}
}


write_revision_file_from_svn_sandbox () {
    # SVN revision:
    svn_cmd info | grep 'Last Changed Rev' >> ${revision_file}
    svn_cmd status | (grep -Ev '^\?' || true) >> ${revision_file}
}


git_cmd () {
    # Run a git command from the top directory
    (cd $PENCIL_HOME; git "$@")
}


svn_cmd () {
    # Run a SVN command from the top directory
    (cd $PENCIL_HOME; svn "$@")
}


main () {
    if [ "$1" = "--print-file-name" -o "$1" = "-p" ]; then
        echo "${revision_file}"
        exit 0
    elif [ "$1" = "--reset" -o "$1" = "-r" ]; then
        write_file=''
    else
        write_file=1
    fi

    reset_locale

    check_prerequisites
    rm -f ${revision_file}

    if [ $write_file ]; then
        write_revision_file
    fi
}


main "$@"