#!/bin/bash
set -euo pipefail
set -x

# If ffmpeg is not installed, exit with an error message
if ! command -v ffmpeg &>/dev/null; then
    printf "Can't find ffmpeg. Please install it (or check your path).\n"
    exit 1
fi

function makeGIF {
    local input=$1
    local framerate=$2
    local width=$3
    local basename=$4
    local maxColors=$5

    # GIFs of 60fps videos have to be 50fps
    if [[ $framerate == "60" ]]; then
        framerate=50
    fi

    if [[ $maxColors == "" ]]; then
        maxColors=256
    fi

    ffmpeg \
        -i "$input" \
        -framerate "$framerate" \
        -vf "fps=$framerate,scale=$width:-1:flags=lanczos,split[s0][s1];[s0]palettegen=max_colors=${maxColors}[p];[s1][p]paletteuse" \
        "${basename}.gif"
}

function makeMP4 {
    local input=$1
    local framerate=$2
    local width=$3
    local basename=$4

    ffmpeg \
        -i "$input" \
        -framerate "$framerate" \
        -vcodec libx264 \
        -pix_fmt yuv420p \
        -an \
        -crf 20 \
        -filter:v scale="$width":-1 \
        "${basename}.mp4"
}

function makeWebM {
    local input=$1
    local framerate=$2
    local width=$3
    local basename=$4

    ffmpeg \
        -i "$input" \
        -framerate "$framerate" \
        -pix_fmt yuv420p \
        -an \
        -crf 30 \
        -b:v 0 \
        -filter:v scale="$width":-1 \
        "${basename}.webm"
}

function requirePostiveInt {
    if [[ ! $2 =~ ^[0-9]+$ ]]; then
        printf "%s must be a positive integer.\n" "$1"
        exit 1
    fi
}

input="$(gum file --header "Input")"
if [[ ! -f "$input" ]]; then
    printf "Input file '%s' does not exist.\n" "$input"
    exit 1
fi

outputBase="$(gum input --header "Output base name" --value="$(basename "${input%.*}")")"
if [[ -z $outputBase ]]; then
    printf "Output base name cannot be empty.\n"
    exit 1
fi

framerate="$(gum input --header "Framerate" --value="24")"
requirePostiveInt "Framerate" "$framerate"

width="$(gum input --header "Width" --value="1920")"
requirePostiveInt "Width" "$width"

type="$(gum choose --header "Output type" "gif" "mp4" "webm")"
if [[ -z $type ]]; then
    printf "No output type selected.\n"
    exit 1
fi

maxColors=""
if [[ $type == "gif" ]]; then
    maxColors="$(gum input --header "Max GIF colors" --value="256")"
    if [[ ! $maxColors =~ ^[0-9]+$ ]]; then
        printf "Max GIF colors must be a positive integer.\n"
        exit 1
    fi
fi

case $type in
gif)
    makeGIF "$input" "$framerate" "$width" "$outputBase" "$maxColors"
    ;;
mp4)
    makeMP4 "$input" "$framerate" "$width" "$outputBase"
    ;;
webm)
    makeWebM "$input" "$framerate" "$width" "$outputBase"
    ;;
*)
    printf "Unknown output type '%s'.\n" "$type"
    exit 1
    ;;
esac