#!/usr/bin/env bash

show_usage() {
    printf """uoeia -- Universally Open Every Image Available

Usage: uoeia [OPTION]... [FILE|URL]

Displays the specified image using your preferred image viewer.

Can open remote urls of individual images, galleries, as well as local files at the same time.
Uses gallery-dl for remote gallery opening - so if gallery-dl can open it, so can your image viewer.

Options:
  -v, --viewer       Specify the image viewer to use.
  -q, --quiet        Don't display any output during normal operation.
  -g, --gdlopts      Pass through options to gallery-dl. Take care to fully quote each passed option.
  -r, --replace      Url patterns to replace in the format 'mypattern:::myreplacement'
  -h, --help         Show this help message and exit.

Examples:
  uoeia my-image.jpg                        Display a local image file.

  uoeia https://example.com/image           Display an image/image gallery from a URL.

  uoeia -v imv https://example.com/image    Display an image from a URL using imv.

  uoeia -g \"--range 1-10\" https://reddit.com/r/earthporn
                                            Download and display the first 10 results.

  uoeia -r 'nitter.net:::twitter.com' https://nitter.net/donttrythis/
                                            Display images from twitter directly instead of its
                                            open source interface nitter.
"
}

die() {
    [ -n "$1" ] && printf '%s\n' "$*" >&2
    exit 1
}

cleanup() {
    rm -f -- "$cache_dir"/*
    rm -r -- "$cache_dir"
}

from_local() {
    fpath="$(realpath -e "$1")"
    ln -s "$fpath" "$cache_dir"
}

# invokes single image downloading or gallery downloading depending on content type
from_remote() {
    link="$(dereference "$1")"
    if curl -sLI "$link" | grep -i '^Content-Type:' | grep -q image; then
        get_single_image "$link"
    else
        get_gallery "$link"
    fi
}

get_gallery() {
    command -v gallery-dl 1>/dev/null 2>&1 || return
    #shellcheck disable=2068
    gallery-dl -D "$cache_dir" ${gal_args[@]} "$1"
}

get_single_image() {
    pwd="$PWD"
    cd "$cache_dir" && curl -sSLO "$1"
    cd "$pwd" || exit 1
}

# unaliases urls which will not be downloaded correctly otherwise
dereference() {
    local output
    # default replacements:
    # teddit to original redd.it hosted picture
    output="${1//teddit.net\/pics\/w:null_/i.redd.it/}"
    output="${output//teddit.net/reddit.com}"
    # nitter to twitter
    output="${output//nitter.net/twitter.com}"

    # custom replacements:
    for rep in "${replacements[@]}"; do
        output="${output//${rep%:::*}/${rep#*:::}}"
    done
    echo "$output"
}

get_imageviewer() {
    for cmd in nsxiv sxiv feh imv vimiv; do
        if command -v "$cmd" 1>/dev/null 2>&1; then program="$cmd"; break; fi
    done
    echo "$program"
}

main() {
    [ -n "$imageviewer" ] || die "Error: Could not find a suitable image viewer, set one manually with the '-v' option."
    command -v "${imageviewer}" 1>/dev/null 2>&1 || die "Error: Opening images in ${imageviewer} requires ${imageviewer} to be installed and and on the path."

    trap cleanup EXIT
    [ -d "$cache_dir" ] || mkdir -p -- "$cache_dir" || die "Error: Can not create cache directory {$cache_dir}"
    im_number=1
    while [ -n "$1" ]; do
        case "$1" in
        *://*.*) from_remote "$1" ;;
        *) from_local "$1" ;;
        esac
        im_number=$((im_number + 1))
        shift
    done

    [ "$(find -L "$cache_dir" -type f -print | wc -l)" -ne 0 ] &&
        ${imageviewer} "$cache_dir"
}

cache_dir="$(mktemp -d)"
imageviewer="$(get_imageviewer)"
gal_args=()
replacements=()

while [[ $# -gt 0 ]]; do
    case "$1" in
    -h | --help)
        show_usage
        exit 0
        ;;
    -q | --quiet)
        gal_args+=("-q")
        ;;
    -v | --viewer)
        imageviewer=$2
        shift 2
        ;;
    -g | --gdlopts)
        if [[ ! "$2" =~ ^- ]]; then
            printf "Error: No valid option passed: %s" "$2"
            break
        fi
        gal_args+=("$2")
        shift 2
        ;;
    -r | --replace)
        replacements+=("$2")
        shift 2
        ;;
    --)
        shift
        break
        ;;
    *)
        if [[ "$1" =~ ^- ]]; then
            printf "Error: Unrecognized option: %s" "$1"
            show_usage
            exit 1
        fi
        arguments+=("$1")
        shift
        ;;
    esac
done
arguments+=("$@")

main "${arguments[@]}"