# Shell functions useful to all shells.


# Helper function to print debug information if $DEBUG is not empty.
#
# Doesn't fit perfectly in this file, but this is the best place to make it
# available everywhere.
source_debug() {
    if [ x$DEBUG != x ]; then
        echo $@
    fi
}

# Sources a configuration file if it exists; loads a fallback .local file if
# it doesn't. If the .local files doesn't exist nothing is sourced.
#
# $1: Path to directory where configuration files are located.
# $2: Directory name in $1 where the non .local files are stored, can be
#     empty. If empty both configuration files (normal and .local) are stored
#     in $1.
# $3: Base name of file in $2, for example "rc" or "env".
# $4: Extension for $3, if this file doesn't exist "$1/$3.local" is sourced.
#     Can be empty, then no extension is used.
# $5: Additional options, set to nolocal to prevent loading of "$1/$3.local"
#                         if "$1/$2/$3.$4" doesn't exist.
#
# Example with the following directory/file structure, $os is Darwin and
# $hostname is marvin.
#
# ~/.zsh
# ~/.zsh/env
# ~/.zsh/env.local
# ~/.zsh/rc
# ~/.zsh/rc.local
# ~/.zsh/host/rc.marvin
# ~/.zsh/os/rc.Darwin
#
# To load additional rc files from within ~/.zsh/rc use the following:
#
# source_config ~/.zsh os   rc $os       # loads os/rc.Darwin
# source_config ~/.zsh host rc $hostname # loads host/rc.marvin
#
# To load additional env files from within ~/.zsh/env use the following (note
# nolocal to prevent loading env.local two times if os and host files don't
# exist):
#
# source_config zsh os   env $os       nolocal # loads os/rc.Darwin
# source_config zsh host env $hostname         # loads env.local
#
# By letting $4 empty normal configuration files can be sourced. A .local can
# still be used.
#
# source_config zsh "" file # loads zsh/file if it exists
#
# Doesn't fit perfectly in this file, but this is the best place to make it
# available everywhere.
#
# If DEBUG is set to a non empty value additional debug output is printed.
source_config() {
    # Path to the file to source and its local counterpart.
    if [ x$4 != x ]; then
        source_file=$1/$2/$3.$4
    # If $4 is empty don't append a trailing dot. This allows source_config()
    # to load normal configuration files.
    else
        source_file=$1/$2/$3
    fi
    source_file_local=$1/$3.local

    # Additional debug output.
    source_debug "source_config(): checking if $source_file exists"
    source_debug "source_config(): checking if $source_file_local exists"

    # If the file does exist then source it.
    if [ -f $source_file ]; then
        source_debug "source_config(): -> sourcing $source_file"
        . $source_file

    # Otherwise load the .local file if it exists and .local files are
    # allowed.
    elif [ -f $source_file_local -a x$5 != xnolocal ]; then
        source_debug "source_config(): -> sourcing $source_file_local"
        . $source_file_local
    else
        source_debug "source_config(): -> neither exists"
    fi

    unset source_file source_file_local
}

# vim: ft=sh