#!/bin/bash

#
# flatten an nginx config
# 
# replaces all occurences of the `include` directive
# with the relevant included files
#
# assumptions:
# - include file paths do not contain spaces
#   (this seems compatible with how nginx handles includes)
# - no files are included from above the directory where the nginx config file
#   being processed resides in

# set debug verbosity to none
[ -z "${NGINX_CONFIG_FLATTEN_DEBUG+x}" ] && NGINX_CONFIG_FLATTEN_DEBUG=""


function debug {
    if [ "$NGINX_CONFIG_FLATTEN_DEBUG" != "" ]; then
        echo "$@" >&2
    fi
}


#
# get the path relative to a different base path
# if the former is relative
# 
# $1 - path
# $2 - base path
function get-path-relative-to {
    # if the path is absolute, that's all we need
    if [[ "$1" = /* ]]; then
        echo "$1"
    else
        echo "$2/$1"
    fi
}


# 
# extract the include paths from an nginx config file
# 
# $1 - the file to work with
function nginx-extract-includes {
    # assumption: include path does not contain spaces
    egrep '^\s*include ' "$1" | sed -r -e "s/^\s*include\s*([^;]+).*$/\1/"
}

# 
# handle all includes of a file to the temporary workdir
# creating the directory structure in the process
# and adding them to the NGINX_CONFIG_FILES variable
# for further processing
# 
# $1 - the file to work with
function nginx-handle-includes {
    # get the included files
    # this will loop through actual globbed filenames
    # 
    # assumption: no files are included from directories above the directory
    # the main config file resides in
    for i in $( nginx-extract-includes "$1" ); do
        debug -n "        +-- found include: $i"
        # if the temporary copy of the file does not exist
        if [ ! -e "$TMP_WORKDIR/$i" ]; then
            debug " - copying!"
            # create the directory structure
            mkdir -p "$TMP_WORKDIR/$( dirname "$i" )"
            # copy the file
            cp "$NGINX_CONFIG_DIR/$i" "$TMP_WORKDIR/$i"
            # add to the list of files to proces
            NGINX_CONFIG_ELEMENTS+=("$i")
        else
            debug " - already copied."
        fi
    done
}


#
# generate a cleaned nginx config directory,
# containing only the files that are included from the config file
# passed as the argument, or files included from those, etc
# 
# $NGINX_CONFIG - nginx config file to work off of
# $OUTPUT_DEST  - target directory (must *not* exist)
function nginx-clean-directory {
    # let's get the file in a temporary location
    # (we don't want to screw up the original!)
    cp "$NGINX_CONFIG" "$TMP_WORKDIR"/

    # go one by one over the NGINX_CONFIG_ELEMENTS array
    # but from the end
    while [[ ${#NGINX_CONFIG_ELEMENTS[@]} > 0 ]]; do
        CUR_INDEX=$(( ${#NGINX_CONFIG_ELEMENTS[@]} - 1 ))
        CUR_ELEMENT=${NGINX_CONFIG_ELEMENTS[$CUR_INDEX]}
        debug "    +-- working with index: $CUR_INDEX"
        debug "        $CUR_ELEMENT"
        unset "NGINX_CONFIG_ELEMENTS[$CUR_INDEX]"
        nginx-handle-includes "$CUR_ELEMENT";
    done
    
    # move the temporary work dir to the output location
    debug "+-- moving the temporary output directory to the final output location"
    debug "    src: $TMP_WORKDIR"
    debug "    dst: $OUTPUT_DEST"
    mv "$TMP_WORKDIR" "$OUTPUT_DEST"
}


#
# flatten an nginx config file,
# including all includes inline, recursively
# 
# $NGINX_CONFIG - nginx config file to work off of
# $OUTPUT_DEST  - where to output the assembled, flattened file (must not exist)
function nginx-flatten {
    
    # let's get the file in a temporary location
    # (we don't want to screw up the original!)
    cp "$NGINX_CONFIG" "$TMP_WORKDIR"/
    NGINX_CONFIG_COPY="$TMP_WORKDIR/$( basename "$NGINX_CONFIG")"

    OLDIFS="$IFS"
    IFS=$'\n'
    while CURRENT_INCLUDES="$( egrep -n '^\s*include\s*.+;.*$' "$NGINX_CONFIG_COPY" )"; do
        PREVIOUS_CI_LINE=0;
        for ci in $CURRENT_INCLUDES; do
            # get the actual file glob
            CI_FILE_GLOB="$( echo "$ci" | sed -r -e "s/^[0-9]+\:\s*include\s*([^;]+).*$/\1/" )"
            CI_LINE="$( echo "$ci" | cut -d ':' -f 1 )"
            CI_INDENT="$( echo "$ci" | cut -d ':' -f 2 | sed -r -e 's/^(\s*).*$/\1/' )"
            DATE_EXT="$( date +%s%N )"
            debug "    +-- previous line : $PREVIOUS_CI_LINE"
            debug "        ci line       : $CI_LINE"
            debug "        indent        : '$CI_INDENT'"
            debug "        glob          : '$CI_FILE_GLOB'"
            tail -n "+$(( $PREVIOUS_CI_LINE + 1 ))" "$NGINX_CONFIG_COPY" | head -n $(( $CI_LINE - 1 - $PREVIOUS_CI_LINE )) > "$NGINX_CONFIG_COPY.$DATE_EXT"
            echo -e "\n$CI_INDENT############################################################\n$CI_INDENT### $CI_FILE_GLOB \n$CI_INDENT############################################################" >> "$NGINX_CONFIG_COPY.$DATE_EXT"
            sed -r -e "s/^/$CI_INDENT/" $CI_FILE_GLOB >> "$NGINX_CONFIG_COPY.$DATE_EXT"
            echo -e "\n$CI_INDENT############################################################\n$CI_INDENT### end $CI_FILE_GLOB \n$CI_INDENT############################################################" >> "$NGINX_CONFIG_COPY.$DATE_EXT"
            PREVIOUS_CI_LINE="$CI_LINE"
        done
        debug "    +-- previous line : $PREVIOUS_CI_LINE"
        debug "        finishing this run off."
        DATE_EXT="$( date +%s%N )"
        tail -n "+$(( $PREVIOUS_CI_LINE + 1 ))" "$NGINX_CONFIG_COPY" > "$NGINX_CONFIG_COPY.$DATE_EXT"
        cat $NGINX_CONFIG_COPY.* > "$NGINX_CONFIG_COPY"
        rm $NGINX_CONFIG_COPY.*
    done
    IFS="$OLDIFS"

    debug "+-- moving the temporary output file to the output destination"
    debug "    src: $NGINX_CONFIG_COPY"
    debug "    dst: $OUTPUT_DEST"
    mv "$NGINX_CONFIG_COPY" "$OUTPUT_DEST"
    debug "+-- cleaning up the temporary output directory"
    rm -rf "$TMP_WORKDIR"
}

function print-usage {
    cat - <<HEREDOC
    
usage:
    $0 <mode> <input_file> <output_file|output_directory>
    
modes:
    
    flatten:
        flatten an nginx config file by inlining all includes recursively,
        save to <output_file>
        
    clean-directory:
        generate a cleaned nginx config directory, containing only the files
        that are included from the input file, or files included from those,
        and so on; output to <output_directory>
    
HEREDOC
}


ORIG_CWD="$PWD"

# we really need 3 arguments:
# $1 - mode of operation
# $2 - source file
# $3 - destination file/directory

if [ "$1" == "" ] || [ "$2" == "" ] || [ "$3" == "" ]; then
    print-usage
    exit 1
fi

# source file exists?
if [ ! -f "$2" ] || [ ! -r "$2" ]; then
    echo
    echo "ERROR: source config file $2 doesn't exist or read access not granted"
    echo
    exit 2
fi

# destination file/directory must not exist
OUTPUT_DEST="$( get-path-relative-to "$3" "$ORIG_CWD" )"
if [ -e "$OUTPUT_DEST" ]; then
    echo
    echo "WARNING: output file/directory exists; quitting!"
    echo
    exit 3
fi


NGINX_CONFIG="$( realpath -eL "$2" )"
debug "+-- config file: '$NGINX_CONFIG'"

NGINX_CONFIG_DIR="$( dirname "$NGINX_CONFIG" )"
debug "    config directory: 'NGINX_CONFIG_DIR'"

cd "$NGINX_CONFIG_DIR"

TMP_WORKDIR="$( mktemp -d /tmp/nginx-conf-flatten.XXXX )"
debug "+-- TMP_WORKDIR: $TMP_WORKDIR"

# the list of files whose includes we have not copied yet
NGINX_CONFIG_ELEMENTS=("$NGINX_CONFIG")


# what are we doing, eh?
if [ "$1" == "flatten" ]; then
    nginx-flatten "$NGINX_CONFIG" "$3"
elif [ "$1" == "clean-directory" ]; then
    nginx-clean-directory "$NGINX_CONFIG" "$3"
else
    print-usage
    exit 1
fi

# get back to the original directory we've been running from
cd "$ORIG_CWD"