#!/bin/bash
# Copyright (C) 2016 Ian Kelling

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at

#     http://www.apache.org/licenses/LICENSE-2.0

# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

cedit() { # [-v] [section_name] FILE

    local s diff name init
    local file_dir="$(dirname "$file")"
    local exists=true
    local verbose=false

    if [[ $1 == -v ]]; then
        verbose=true
        shift
    fi
    if (( $# == 2 )); then
        name=": $1"
        shift
    fi

    local file="$1"
    local file_name="${file##*/}"

    local begin="#_#_# start delimiter of cedit section$name. do not modify. #_#_#"
    local end="#_#_# end delimiter of cedit section$name. do not modify. #_#_#"

    if [[ ! -e $file_dir ]]; then
        if ! mkdir -p $file_dir; then
            s=sudo
            $s mkdir -p $file_dir || return 1
        fi
    fi
    if [[ ! -e $file ]]; then
        exists=false
        if ! $s touch $file; then
            s=sudo
            $s touch $file || return 1
        fi
    fi

    [[ -w $file ]] || s=sudo


    if $exists; then
        local temp="$(mktemp -d)/$file_name"
        cp "$file" "$temp"
        cp /dev/null "$file"
        local in_section=false
        while IFS= read -r line; do
            if [[ $line == $begin ]]; then
                in_section=true;
            fi
            if ! $in_section; then
                printf '%s\n' "$line" >> $file
            fi
            if [[ $line == $end ]]; then
                in_section=false;
            fi
        done < "$temp"
    fi

    IFS= read -d '' -n 1 -r init
    if [[ $init ]]; then
        $s tee -a "$file" >/dev/null <<<"$begin"
        printf '%s' "$init" | $s tee -a "$file" >/dev/null
        $s tee -a "$file" >/dev/null
        $s tee -a "$file" >/dev/null <<<"$end"
    fi

    if ! $exists; then
        ret=0
        if $verbose; then
            echo "New file $file:"
            cat "$file"
        fi
    elif type -t diff &>/dev/null; then
        diff=$(diff -u "$temp" "$file")
        ret=$?
        if $verbose; then
            if (( $ret == 0 )); then
                echo "No changes made to $file"
            fi
        else

            echo "backup of original at $temp"
            echo diff -u "$temp" "$file":
            echo "$diff"
        fi
    else
        diff=$(cmp "$temp" "$file")
        ret=$?
        if $verbose; then
            echo "$diff"
        fi
    fi
    return $ret
}
cedit "$@"