#!/usr/bin/env sh

config_file=.version.json
changelog_file=CHANGELOG.md
changelog_header="# Changelog

All notable changes to this project will be documented in this file. See [Conventional Commits](https://www.conventionalcommits.org/en/v1.0.0/) for commit guidelines.

This project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).

----
"

reverse() {
    if which tac >/dev/null 2>&1; then
        tac
    else
        tail -r
    fi
}

generate_config() {
    jq --null-input --arg version "0.0.0" --arg sha "" '{ "version": $version, "sha": $sha}' > $config_file
}

update_config() {
    sha="$(git rev-parse --short HEAD)"
    config=$(jq '.sha |= $sha | .version |= $version' --arg sha "$sha" --arg version "$1" $config_file)
    echo "$config" > $config_file
}

calculate_version() {
    version_number=$(echo "$1" | cut -d'-' -f1 | cut -d'+' -f1)
    pre_release=$(echo "$1" | cut -d'-' -f2 | cut -d'+' -f1)
    build=$(echo "$1" |cut -d'-' -f2 | cut -d'+' -f2)
    if [ "$pre_release" = "$1" ]; then
        pre_release=""
    fi
    if [ "$build" = "$1" ] || [ "$build" = "$pre_release" ]; then
        build=""
    fi

    major=$(echo "$version_number" | cut -d'.' -f1)
    minor=$(echo "$version_number" | cut -d'.' -f2)
    patch=$(echo "$version_number" | cut -d'.' -f3)
    pre_release_identifier=$(echo "$pre_release." | cut -d'.' -f2)

    pre_release=""
    build=""

    case "$2" in
        major)
            if [ -n "$major" ]; then
                major=$((major+1))
                minor=0
                patch=0
            fi
        ;;

        minor)
            if [ -n "$minor" ]; then
                minor=$((minor+1))
                patch=0
            fi
        ;;

        patch)
            if [ -n "$patch" ]; then
                patch=$((patch+1))
            fi
        ;;

        rc)
            if [ -z "$pre_release_identifier" ]; then
                pre_release_identifier=1
            else
                pre_release_identifier=$((pre_release_identifier+1))
            fi
            pre_release="rc.$pre_release_identifier"
        ;;
    esac

    if [ "$3" = "build" ]; then
        build="$(git rev-parse --short HEAD)"
    fi

    version_number="${major}.${minor}.${patch}"
    if [ -n "$pre_release" ]; then
        pre_release="-$pre_release"
    fi
    if [ -n "$build" ]; then
        build="+$build"
    fi

    echo "${version_number}${pre_release}${build}"
}

get_git_commits() {
    since_hash="$(jq '.sha' < $config_file | tr -d '"')"
    if [ -n "$since_hash" ]; then
        git rev-list "$since_hash..HEAD"
    else
        git rev-list HEAD
    fi
}

get_git_commit_subject() {
    git show -s --format=%s "$1"
}

get_git_commit_body() {
    git show -s --format=%b "$1"
}

get_commit_type() {
    echo "$1" | sed -r -n 's/([a-z]+)(\(?|:?).*/\1/p' | tr '[:upper:]' '[:lower:]'
}

get_commit_scope() {
    echo "$1" | sed -r -n 's/[a-z]+\(([^)]+)\).*/\1/p'
}

get_commit_description() {
    echo "$1" | sed -r -n 's/.*:[ ]+(.*)/\1/p'
}

get_commit_footer() {
    with_colon=$(echo "$1" | sed -n '/^[A-Za-z-]\{1,\}: /,//{p;}')
    with_hash=$(echo "$1" | sed -n '/^[A-Za-z-]\{1,\} #/,//{p;}')
    fallback=$(echo "$1" | reverse | awk '/^$/{exit}1' | reverse)

    if [ -z "$with_colon" ] && [ -z "$with_hash" ]; then
        echo "$fallback"
    elif [ ${#with_colon} -gt ${#with_hash} ]; then
        echo "$with_colon"
    else
        echo "$with_hash"
    fi
}

get_commit_body() {
    pattern=$(get_commit_footer "$1" | head -n 1)
    if [ -n "$pattern" ]; then
        echo "$1" | sed -e "/$pattern/,\$d"
    else
        echo "$1"
    fi
}

is_breaking_change() {
    if echo "$1" | grep -q '!' || echo "$2" | grep -q 'BREAKING[ -]CHANGE: '; then
        echo 1
    else
        echo 0
    fi
}

get_breaking_change() {
    with_colon=$(echo "$1" | sed -n  '/^BREAKING[ -]CHANGE: /,/^[A-Za-z-]\{1,\}: /{ s/BREAKING[ -]CHANGE: \(.*\)/\1/; /^[A-Za-z-]\{1,\}: /!p;}')
    with_hash=$(echo "$1" | sed -n  '/^BREAKING[ -]CHANGE: /,/^[A-Za-z-]\{1,\} #/{ s/BREAKING[ -]CHANGE: \(.*\)/\1/; /^[A-Za-z-]\{1,\} #/!p;}')
    if [ -n "$with_colon" ] && ! echo "$with_colon" | grep -q '[A-Za-z-]\{1,\} #'; then
        echo "$with_colon"
    else
        echo "$with_hash"
    fi
}

generate_changelog_entry() {
    is_major=0
    is_minor=0
    is_patch=0

    version="$(jq '.version' < $config_file | tr -d '"')"

    breakingchanges="### BREAKING CHANGES\n"
    features="### Features\n"
    bugfixes="### Bug fixes\n"
    builds="### Build System"
    chores="### Chores\n"
    test="### Chores\n"

    for commit in $(get_git_commits); do
        git_subject=$(get_git_commit_subject "$commit")
        git_body=$(get_git_commit_body "$commit")

        type=$(get_commit_type "$git_subject")
        scope=$(get_commit_scope "$git_subject")
        description=$(get_commit_description "$git_subject")
        body=$(get_commit_body "$git_body")
        footer=$(get_commit_footer "$git_body")
        breakingchange=$(get_breaking_change "$footer")
        is_breaking=$(is_breaking_change "$git_subject" "$footer")

        if [ -n "$scope" ]; then
            entry="**$scope:** $description"
        else
            entry="$description"
        fi
        entry=$(echo "$entry" | sed -e '2,$s/^[ ]*/  /')

        if [ "$is_breaking" -eq 1 ] && [ -z "$breakingchange" ]; then
            breakingchange="$body"
        fi

        if [ "$is_breaking" -eq 1 ]; then
            is_major=1
            breakingchange=$(echo "$breakingchange" | sed -e '2,$s/^[ ]*/  /')
            breakingchanges="$breakingchanges\n* $breakingchange\n"
        fi

        case "$type" in
            feat)
                is_minor=1
                features="$features\n* $entry\n"
            ;;
            
            fix)
                is_patch=1
                bugfixes="$bugfixes\n* $entry\n"
            ;;

            build)
                builds="$builds\n* $entry\n"
            ;;

            chore)
                chores="$chores\n* $entry\n"
            ;;

            ci)
            ;;

            docs)
            ;;

            style)
            ;;

            refactor)
            ;;

            perf)
            ;;

            test)
            ;;

            revert)
            ;;
        esac
    done

    if [ $is_major -eq 1 ]; then
        version=$(calculate_version "$version" "major")
    elif [ $is_minor -eq 1 ]; then
        version=$(calculate_version "$version" "minor")
    elif [ $is_patch -eq 1 ]; then
        version=$(calculate_version "$version" "patch")
    fi

    update_config "$version"

    entry=""

    if [ "$breakingchanges" !=  "### BREAKING CHANGES\n" ]; then
        entry="$entry$breakingchanges\n\n"
    fi
    if [ "$bugfixes" != "### Bug fixes\n" ]; then
        entry="$entry$bugfixes\n\n"
    fi
    if [ "$features" != "### Features\n" ]; then
        entry="$entry$features\n\n"
    fi

    if [ -n "$entry" ]; then
        entry="## [$version] ($(date '+%Y-%m-%d'))\n\n\n$entry"
    fi

    echo "$entry"
}


new_changelog() {
    echo "$changelog_header" > $changelog_file
}

new_changelog_entry() {
    entry=$(generate_changelog_entry)
    if [ -n "$entry" ]; then
        changelog=$(sed -n '/^----/,//{/^----/!p;}' < $changelog_file)
        if [ -n "$changelog" ]; then
            changelog="$changelog_header\n$entry\n$changelog"
        else
            changelog="$changelog_header\n$entry"
        fi
        echo "$changelog" > $changelog_file
    fi
}

init() {
    if [ ! -f "$config_file" ]; then
        echo "Generating a config ... "
        generate_config
        new_changelog
    else
        echo "Using existing config"
    fi

    new_changelog_entry
}

init