#!/bin/bash
# ----------------------------------------
# codewars-kata-download
#
# Download kata from codewars using the codewars site api.
#
# This generate a directory with the following files:
#
# * description.md: description for the kata.
# * solution.xx: template file for the solution.
# * tests.xx: template file with some tests.
#
# Copyright 2017, Juan Picca <jumapico@gmail.com>
#
# LICENSE: MIT
# ----------------------------------------

set -e


#
# Show usage
#
usage() {
    cat >&2 <<'END'

Usage: codewars-download-kata access-token slug language

    access-token:
        Value under "API ACCESS TOKEN" in the "Account Settings" page, url
        <https://www.codewars.com/users/edit>.

    slug:
        Value taken from the url of the kata.
        Example: correct-the-time-string in the url
        <https://www.codewars.com/kata/correct-the-time-string/train/cpp>.

    language:
        Language for a given kata.
        The available languages for a kata are displayed in the "language" combo
        box of the kata. This parameter is the same of the url.
        Example: cpp in the url
        <https://www.codewars.com/kata/correct-the-time-string/train/cpp>.

END
}


#
# Return in the global variable LANGUAGE_EXTENSION the extension file from a
# given language.
# Aborts if no conversion exists.
#
# Params:
# * language
#
language2extension() {
    local language="$1"

    case $language in
        c)
            LANGUAGE_EXTENSION="c"
            ;;
        cpp)
            LANGUAGE_EXTENSION="cpp"
            ;;
        csharp)
            LANGUAGE_EXTENSION="cs"
            ;;
        *)
            echo "Unknown language '$language' - aborting." >&2
            exit 1
    esac
}


#
# Write to stdout a script to test the kata in the given language.
#
# Params:
# * language
# * extension
#
generate_run_script() {
    local language="$1"
    local extension="$2"

    cat <<'END'
#!/bin/sh
CACHEDIR="$HOME/.cache/codewars-runner-cli"
if [ ! -d "$CACHEDIR" ]; then
    (cd "$(dirname "$CACHEDIR")"; git clone --depth=1 "https://github.com/Codewars/codewars-runner-cli.git")
else
    (cd "$CACHEDIR"; git pull)
fi
END
    cat <<END
docker-compose -f "\$CACHEDIR/docker-compose.yml" \
    run --rm $language -c "\$(cat solution.$extension)" -f "\$(cat tests.$extension)"
END
}

#
# Download files related to the kata referenced by the slug in codewars.
# Abort if found errors.
#
# Params:
# * access-token
# * slug
# * language
#
download_kata() {
    local accesstoken="$1"
    local slug="$2"
    local language="$3"

    local extension dir output body

    language2extension "$language"
    extension="$LANGUAGE_EXTENSION"
    dir="${slug}_${extension}"

    if [ -d "$dir" ]; then
        echo "The directory '$dir' already exist - aborting." >&2
        exit 1
    fi
    output="$(curl --silent --include --location \
        --request POST \
        --header "Authorization: $accesstoken" \
        "https://www.codewars.com/api/v1/code-challenges/${slug}/${language}/train")"
    if [ 200 != "$(echo "$output" | head -n +1 | cut -d' ' -f2)" ]; then
        cat >&2 <<END
Unexpected response from codewars - aborting.

Check using:

    curl --silent --include --location --request POST --header "Authorization: $accesstoken" "https://www.codewars.com/api/v1/code-challenges/${slug}/${language}/train"
END
        exit 1
    fi
    body="$(echo "$output" | sed '1,/^\r$/d')"

    mkdir "$dir"
    cat > "$dir/description.md" <<END
# $(echo "$body" | jq -r '.name')

**($slug)**

---

END
    echo "$body" | jq -r '.description' >> "$dir/description.md"
    echo "$body" | jq -r '.session.setup' > "$dir/solution.$extension"
    echo "$body" | jq -r '.session.exampleFixture' > "$dir/tests.$extension"

    generate_run_script $language $extension > "$dir/run.sh"
    chmod +x "$dir/run.sh"
}

#
# Entry point
#
main() {
    if [ $# -ne 3 ]; then
        usage
        exit 1
    fi
    download_kata "$@"
}

main "$@"