#!/usr/bin/env zsh
# Output commands to generate animated images from files

setopt LOCAL_OPTIONS ERR_RETURN NO_UNSET PIPE_FAIL

zmodload zsh/zutil
local -a o_help=()
local -a o_delay=()
local -a o_blend=()
local -a o_reverse=()
zparseopts -D -K -- h=o_help -help=o_help \
    -delay:=o_delay -blend=o_blend -reverse=o_reverse
if [[ ${#o_help} -ne 0 || ! -v 1 ]]; then
    local ret=$(( ${#o_help} ^ 1 ))
    print -u $(( 1 + ${ret} )) \
        "usage: ${0} [-h|--help] [--delay MILLISECONDS] [--blend] [--reverse]" \
        "<FILES>"
    return ${ret}
fi

local delay=100
[[ ${#o_delay} -eq 2 ]] && delay=${o_delay[2]}
local blend="-b"
[[ ${#o_blend} -ne 0 ]] && blend="+b"

local -a cmd
if [[ ${1##*.} == "webp" ]]; then
    cmd=(webpmux -o output.webp)
    for file in ${@}; do
        cmd+=(-frame ${file} +${delay}+0+0+0${blend})
    done
    if [[ ${#o_reverse} -ne 0 ]]; then
        cmd[-1]=+$((${delay} * 2))+0+0+0${blend}
        cmd[6]=+$((${delay} * 2))+0+0+0${blend}
        for file in ${(Oa)@:2:-1}; do
            cmd+=(-frame ${file} +${delay}+0+0+0${blend})
        done
    fi
elif [[ ${1##*.} == "png" ]]; then
    cmd=(apngasm --output output.png)
    for file in ${@}; do
        cmd+=(${file} ${delay})
    done
    if [[ ${#o_reverse} -ne 0 ]]; then
        cmd[-1]=$((${delay} * 2))
        cmd[5]=$((${delay} * 2))
        for file in ${(Oa)@:2:-1}; do
            cmd+=(${file} ${delay})
        done
    fi
else
    print -u 2 "file format not supported"
    return 1
fi
if [[ -o INTERACTIVE ]]; then
    print -z "" ${cmd}
else
    print "" ${cmd}
fi