#!/bin/sh

# wcurl - a simple wrapper around curl to easily download files.
#
# Requires curl >= 7.46.0 (2015)
#
# Copyright (C) Samuel Henrique, <samueloph@debian.org>.
# Copyright (C) Sergio Durigan Junior, <sergiodj@debian.org>
# Copyright (C) Ryan Carsten Schmidt <git@ryandesign.com>
# Copyright (C) Ben Zanin
#
# Permission to use, copy, modify, and distribute this software for any purpose
# with or without fee is hereby granted, provided that the above copyright
# notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT OF THIRD PARTY RIGHTS. IN
# NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
# DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR
# OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE
# OR OTHER DEALINGS IN THE SOFTWARE.
#
# Except as contained in this notice, the name of a copyright holder shall not be
# used in advertising or otherwise to promote the sale, use or other dealings in
# this Software without prior written authorization of the copyright holder.
#
# SPDX-License-Identifier: curl

# Stop on errors and on usage of unset variables.
set -eu

VERSION="2024.07.10"

PROGRAM_NAME="$(basename "$0")"
readonly PROGRAM_NAME

# Display the version.
print_version()
{
    cat << _EOF_
${VERSION}
_EOF_
}

# Display the program usage.
usage()
{
    cat << _EOF_
${PROGRAM_NAME} -- a simple wrapper around curl to easily download files.

Usage: ${PROGRAM_NAME} [--curl-options <CURL_OPTIONS>] [--dry-run] [--] <URL>...
       ${PROGRAM_NAME} [--curl-options=<CURL_OPTIONS>] [--dry-run] [--] <URL>...
       ${PROGRAM_NAME} -h|--help
       ${PROGRAM_NAME} -V|--version

Options:

  --curl-options <CURL_OPTIONS>: Specify extra options to be
                                 passed when invoking curl. May be
                                 specified more than once.

  --dry-run: Don't actually execute curl, just print what would be
             invoked.

  -V,--version: Print version information.

  -h,--help: Print this usage message.

  <URL>: The URL to be downloaded.  May be specified more than once.
_EOF_
}

# Display an error message and bail out.
error()
{
    printf "%s\n" "$*" > /dev/stderr
    exit 1
}

# Extra curl options provided by the user.
# This will be set per-URL for every URL provided.
# Some options are global, but we are erroring on the side of needlesly setting
# them multiple times instead of causing issues with parameters that needs to
# be set per-URL.
CURL_OPTIONS=""

# The URLs to be downloaded.
URLS=""

# The parameters that will be passed per-URL to curl.
readonly PER_URL_PARAMETERS="\
    --fail \
    --globoff \
    --location \
    --proto-default https \
    --remote-name-all \
    --remote-time \
    --retry 10 \
    --retry-max-time 10 "

# Whether to invoke curl or not.
DRY_RUN="false"

# Sanitize parameters.
sanitize()
{
    if [ -z "${URLS}" ]; then
        error "You must provide at least one URL to download."
    fi

    readonly CURL_OPTIONS URLS DRY_RUN
}

# Execute curl with the list of URLs provided by the user.
exec_curl() {
    CMD="curl "

    # Store version to check if it supports --no-clobber and --parallel.
    curl_version=$($CMD --version | cut -f2 -d' ' | head -n1)

    # --no-clobber is only supported since 7.83.0.
    # --parallel is only supported since 7.66.0.
    if [ "$(echo "$curl_version" | cut -f1 -d.)" -ge 8 ]; then
        CURL_HAS_NO_CLOBBER="--no-clobber"
        CURL_HAS_PARALLEL="--parallel"
    elif [ "$(echo "$curl_version" | cut -f1 -d.)" -eq 7 ];then
        if [ "$(echo "$curl_version" | cut -f2 -d.)" -ge 83 ]; then
            CURL_HAS_NO_CLOBBER="--no-clobber"
        else
            CURL_HAS_NO_CLOBBER=""
        fi
        if [ "$(echo "$curl_version" | cut -f2 -d.)" -ge 66 ]; then
            CURL_HAS_PARALLEL="--parallel"
        else
            CURL_HAS_PARALLEL=""
        fi
    else
        CURL_HAS_NO_CLOBBER=""
        CURL_HAS_PARALLEL=""
    fi

    # Detecting whether we need --parallel.  It's easier to rely on
    # the shell's argument parsing.
    # shellcheck disable=SC2086
    set -- $URLS

    if [ "$#" -gt 1 ]; then
        CURL_PARALLEL="$CURL_HAS_PARALLEL"
    else
        CURL_PARALLEL=""
    fi

    # Start assembling the command.
    #
    # We use 'set --' here (again) because (a) we don't have arrays on
    # POSIX shell, and (b) we need better control over the way we
    # split arguments.
    #
    # shellcheck disable=SC2086
    set -- ${CMD} ${CURL_PARALLEL}

    NEXT_PARAMETER=""
    for url in ${URLS}; do
        # shellcheck disable=SC2086
        set -- "$@" ${NEXT_PARAMETER} ${PER_URL_PARAMETERS} ${CURL_HAS_NO_CLOBBER} ${CURL_OPTIONS} "${url}"
        NEXT_PARAMETER="--next"
    done

    if [ "${DRY_RUN}" = "false" ]; then
        exec "$@"
    else
        printf "%s\n" "$@"
    fi
}

# Use "${1-}" in order to avoid errors because of 'set -u'.
while [ -n "${1-}" ]; do
    case "${1}" in
        --curl-options=*)
            opt=$(printf "%s\n" "${1}" | sed 's/^--curl-options=//')
            CURL_OPTIONS="${CURL_OPTIONS} ${opt}"
            ;;

        --curl-options)
            shift
            CURL_OPTIONS="${CURL_OPTIONS} ${1}"
            ;;

        --dry-run)
            DRY_RUN="true"
            ;;

        -h|--help)
            usage
            exit 0
            ;;

        -V|--version)
            print_version
            exit 0
            ;;

        --)
            # This is the start of the list of URLs.
            shift
            for url in "$@"; do
                # Encode whitespaces into %20, since wget supports those URLs.
                newurl=$(printf "%s\n" "${url}" | sed 's/ /%20/g')
                URLS="${URLS} ${newurl}"
            done
            break
            ;;

        -*)
            error "Unknown option: '$1'."
            ;;

        *)
            # This must be a URL.
            # Encode whitespaces into %20, since wget supports those URLs.
            newurl=$(printf "%s\n" "${1}" | sed 's/ /%20/g')
            URLS="${URLS} ${newurl}"
            ;;
    esac
    shift
done

sanitize
exec_curl