#!/bin/bash


revision_file='revision.txt'


usage() {
    cat <<EOT
Usage:
  pc_identify_revision [--reset|-r] [--print-file-name|-p]

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.

Examples:
  pc_identify_revision                    # Print revision and diff
  pc_identify_revision --one-line         # Print revision
  pc_identify_revision --print-file-name  # Print name of rev. file
  pc_identify_revision --write            # Write rev. and diff to file
  pc_identify_revision --reset            # Delete revision file
EOT
}


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 () {
    printf 'Revision: '
    if [ -d "${PENCIL_HOME}/.git" ]; then
        write_revision_from_git_sandbox
    elif [ -d "${PENCIL_HOME}/.svn" ]; then
        write_revision_from_svn_sandbox
    else
        echo 'Warning: Cannot determine a revision number'
    fi
}


write_revision_from_git_sandbox () {
    revision="$(git_cmd rev-parse --short HEAD)"
    mypath="$(pwd)"
    if ! [[ $mypath =~ .*$PENCIL_HOME.* ]]; then
        sed -i -e 's/cvsid *=.*$/cvsid="'$revision'"/' ../start.in
        sed -i -e 's/cvsid *=.*$/cvsid="'$revision'"/' ../run.in
    fi
    modified="$(git_cmd status --short --untracked-files=no)"
    if [ "$one_line" ]; then
        if [ "$modified" ]; then
            echo "${revision}+"
        else
            echo "$revision"
            fi
    else
        echo "$revision"
        echo "$modified"
    fi
}


write_revision_from_svn_sandbox () {
    revision="$(svn_cmd info | grep 'Last Changed Rev')"
    modified="$(svn_cmd status | (grep -Ev '^\?' || true))"
    if [ "$one_line" ]; then
        if [ "$modified" ]; then
            echo "${revision}+"
        else
            echo "$revision"
            fi
    else
        echo "$revision"
        echo "$modified"
    fi
}


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 () {
    write_file=''
    one_line=''

    for arg in "$@"; do
        if [ "$arg" = "--help" ] || [ "$arg" = "-h" ]; then
            usage
            exit 0
        elif [ "$arg" = "--print-file-name" ] || [ "$arg" = "-p" ]; then
            echo "${revision_file}"
            exit 0
        elif [ "$arg" = "--reset" ] || [ "$arg" = "-r" ]; then
            rm -f "${revision_file}"
            exit 0
        elif [ "$arg" = "--write" ] || [ "$arg" = "-w" ]; then
            write_file=1
        elif [ "$arg" = "--one-line" ] || [ "$arg" = "-o" ]; then
            one_line=1
        fi
    done

    reset_locale

    check_prerequisites

    if [ "$write_file" ]; then
        rm -f ${revision_file}
        write_revision > ${revision_file}
    else
        write_revision
    fi
}


main "$@"