-- SimpleSlides.lua
--
-- Version 0.2
--
-- By John Hartman
--
-- Thanks to tid-kijyun, whose tally-counter.lua I used as a framework.
-- https://gist.github.com/tid-kijyun/477c723ea42d22903ebe6b6cee3f77a1
--

--[[
The OBS Image Slide Show source loads all images into video memory. That
lets it change slides without rendering lags, but limits the size of the
slideshow, since UNCOMPRESSED images are used, and video memory is a limited
resource.

This script avoids the memory problem by simply loading a new image file into
an Image Source for each slide. The trade off is that some frames may be
dropped during image changes due to rendering lag.
On my PC with an i7 and Intel HD4600 graphics, it drops the same number of
frames as are dropped if you manually change the filespec for an Image Source:
no drops for 1280x720 images, up to 4 frames dropped for 3306x1860 images.
If a scene contains only the slide, drops are hard to see. 
If a scene also has a camera or other moving source, it can be noticeable.

I wrote this to display PowerPoint or LibreOffice Impress slides, exported as
images, allowing an operator to run a stream without needing to switch back and
forth between PowerPoint and OBS.
I use an on-line PPTX-to-image service, which generates 3306x1860 images, and
using these causes frames to be dropped. Since my stream is only 1280x720, I used
Microsoft PowerToys to rescale all the images to 1280x720, eliminating the drop.
--]]

obs = obslua

-- The name of our controlling Sources must begin with this string
source_key = 'SimpleSlides:'

-- We accept files with the following extensions (acceptable to the Image Source)
allowed_filetypes = {
    ["png"] = true,
    ["jpg"] = true,
    ["jpeg"] = true,
    ["bmp"] = true,
    ["gif"] = true,
}
    
-- A table of slide show data, indexed by Source name.
-- Each entry contains a sorted list of filenames, and the index of the current slide.
slide_shows = {}

-- The currently active slideshow: hotkeys and buttons apply to this one
active_source_name  = ""

hotkey_reset_id    = obs.OBS_INVALID_HOTKEY_ID
hotkey_next_id     = obs.OBS_INVALID_HOTKEY_ID
hotkey_previous_id = obs.OBS_INVALID_HOTKEY_ID

-- script_description returns the description shown to the user
function script_description()
    print("in script_description")
    return [[<h2>SimpleSlides</h2>
            <p>Use an Image Source whose name begins with "SimpleSlides:" to
            display sequential image files from a directory, creating a simple
            slide show without the memory limitations of the OBS Image Slide
            Show. However, some frames may be dropped during image changes.</p>
            
            <p>The filespec in the Image Source is used to specify the directory.
            Files of type png, jpg, jpeg, bmp, and gif will be shown.
            Files are shown in sort order: XXX1 will be followed
            by XXX10, not by XXX2, so you may need to normalize
            your filenames (XXX01, XXX02...)</p>

            <p>Slides may be changed via assignable hotkey, or via the buttons
            below. Hotkeys and buttons act only if a SimpleSlide Image Source
            is visible in the Preview or Program window.</p>
            
            <p>You can have multiple independent slide shows using Sources with
            unique names: for example "SimpleSlides: lyrics" and
            "SimpleSlides: sermon graphics". Hotkeys and buttons will act on
            whichever slideshow is visible in the Preview or Program window,
            with Program taking precedence.</p>
           ]]
end

----------------------------------------------------------
-- script_properties defines the properties that the user
-- can change for the entire script module itself
function script_properties()
    print("in script_properties")
    
    local props = obs.obs_properties_create()
    obs.obs_properties_add_button(props, "next_button",     " NEXT ", next_button_clicked)
    obs.obs_properties_add_button(props, "previous_button", " PREV ", previous_button_clicked)
    obs.obs_properties_add_button(props, "reset_button",    "RESET",  reset_button_clicked)

    return props
end

-- script_update is called when script settings are changed
function script_update(settings)
    print('in script_update')
end

-- script_defaults is called to set the default settings
function script_defaults(settings)
    print("in script_defaults")
end

-- script_save is called when the script is saved
-- We save our hotkey assignments
function script_save(settings)
    print("in script_save")
    local save_array = obs.obs_hotkey_save(hotkey_reset_id)
    obs.obs_data_set_array(settings, "reset_hotkey", save_array)
    obs.obs_data_array_release(save_array)

    save_array = obs.obs_hotkey_save(hotkey_next_id)
    obs.obs_data_set_array(settings, "next_slide_hotkey", save_array)
    obs.obs_data_array_release(save_array)
    
    save_array = obs.obs_hotkey_save(hotkey_previous_id)
    obs.obs_data_set_array(settings, "previous_slide_hotkey", save_array)
    obs.obs_data_array_release(save_array)
end

-- script_load is called on startup
function script_load(settings)
    print("in script_load")
    obs.obs_frontend_add_save_callback(on_save)
    obs.obs_frontend_add_event_callback(handle_frontend_event)

    -- Connect our hotkeys
    hotkey_reset_id = obs.obs_hotkey_register_frontend("simpleslides_reset_button", "[SimpleSlides]Reset", reset)
    hotkey_next_id  = obs.obs_hotkey_register_frontend("simpleslides_next_button", "[SimpleSlides]Next", next_slide)
    hotkey_previous_id = obs.obs_hotkey_register_frontend("simpleslides_previous_button", "[SimpleSlides]Previous", previous_slide)

    local save_array = obs.obs_data_get_array(settings, "reset_hotkey")
    obs.obs_hotkey_load(hotkey_reset_id, save_array)
    obs.obs_data_array_release(save_array)

    save_array = obs.obs_data_get_array(settings, "next_slide_hotkey")
    obs.obs_hotkey_load(hotkey_next_id, save_array)
    obs.obs_data_array_release(save_array)
    
    local save_array = obs.obs_data_get_array(settings, "previous_slide_hotkey")
    obs.obs_hotkey_load(hotkey_previous_id, save_array)
    obs.obs_data_array_release(save_array)

    -- See if a slideshow is active
    -- (when the script is reloaded - during startup, no scenes loaded yet)
    select_slideshow("script_load")
end

-- on_save(loading) is called at startup and when a scene collection is loaded.
-- on_save(saving) is called when anything in a scene_collection is changed, 
-- just before a new scene collection is loaded, and during showdown.
function on_save(save_data, saving, private_data)
	print( "on_save(" .. (saving and "saving)" or "loading)"))
	if not saving then
        -- TODO: loading a new scene-set should wipe all slideshow data.
        select_slideshow("on_save(load)")
    else
        -- TODO: a change to one of our sources should reset its slideshow data
        -- But on_save is called for ANY save, of anything.
        select_slideshow("on_save(save)")
	end
end

function handle_frontend_event(event)
	if event == obs.OBS_FRONTEND_EVENT_SCENE_CHANGED then
        -- get a preview event before this anyway, so avoid duplicate action
        print("OBS_FRONTEND_EVENT_SCENE_CHANGED")
    elseif event == obs.OBS_FRONTEND_EVENT_PREVIEW_SCENE_CHANGED then
        select_slideshow("OBS_FRONTEND_EVENT_PREVIEW_SCENE_CHANGED")
    elseif event == obs.OBS_FRONTEND_EVENT_SCENE_LIST_CHANGED then
       print("OBS_FRONTEND_EVENT_SCENE_LIST_CHANGED")
	elseif event == obs.OBS_FRONTEND_EVENT_EXIT then
	   print("OBS_FRONTEND_EVENT_EXIT")
	elseif event == obs.OBS_FRONTEND_EVENT_FINISHED_LOADING then
	   print("OBS_FRONTEND_FINISHED_LOADING")
    else
       print("Front end event " .. event)
    end
end

-- Given a path, return the directory part (including final slash or backslash)
-- file part, extension part (not including dot)
-- if there's no directory part, or extension, some strings may be empty
-- Yes, I know you could do it in one line using regex.
function splitpath(filespec)
    local path, name, extension

    local i = #filespec
    while i > 0 do
        local ch = string.sub(filespec,i,i)
        if ch == '\\' or ch == '/' then break end
        i = i - 1
    end

    if i == 0 then
        path = ''
    else
        path = string.sub(filespec,1,i)
    end

    local j = #filespec
    while j > i+1 do
        local ch = string.sub(filespec,j,j)
        if ch == '.' then break end
        j = j - 1
    end

    if j == i+1 then
        name = string.sub(filespec,i+1)
        extension = ''
    else
        name = string.sub(filespec,i+1,j-1)
        extension = string.sub(filespec,j+1)
    end
    
    return path, name, extension
end

-- If we don't have slideshow data for special_image_name, create it now
function create_slideshow_if_needed(special_image_name)
    if slide_shows[special_image_name] then
        print('Slideshow exists for "' .. special_image_name .. '"')
    else
        print('Creating slideshow for "' .. special_image_name .. '"')

        local show = {}
        
        local source = obs.obs_get_source_by_name(special_image_name)
        if source == nil then 
            print('ERROR: no source for "' .. special_image_name .. '"')
        else
            -- Filespec is as entered when the source was created, possibly
            -- changed if the scene was saved after we advanced to another slide.
            -- We extract the parts we need (currently just the path)
            local settings = obs.obs_source_get_settings(source)
            if not settings then
                print('ERROR: no settings for "' .. special_image_name .. '"')
            else
                local filespec = obs.obs_data_get_string(settings, 'file')
                obs.obs_data_release(settings)
                
                local path, name, extension
                path, name, extension = splitpath(filespec)
                print('Filespec="' .. filespec .. '" path="' .. path .. '" name="' .. name .. '" ext="' .. extension .. '"')

                local filenames = {}
                local dir = obslua.os_opendir(path)
                local entry
                repeat
                    entry = obslua.os_readdir(dir)
                    if entry and not entry.directory then
                        local xpath
                        xpath, name, extension = splitpath(entry.d_name)

                        if allowed_filetypes[string.lower(extension)] then
                            -- print('  Image file="' .. entry.d_name .. '"')
                            table.insert(filenames, path .. entry.d_name)
                        end
                    end
                until not entry
                obslua.os_closedir(dir)
                
                -- Alphabetize (case insensitive) the filenames
                table.sort(filenames, function(a,b) return string.lower(a) < string.lower(b) end )

                -- Save the slideshow for later use
                show['filenames'] = filenames
                show['current_slide'] = 1
                slide_shows[special_image_name] = show

                do_slide('from create_slideshow_if_needed', 'SHOW_SLIDE')
            end
            obs.obs_source_release(source)
        end
    end
end

-- If the scene has a source_key source, return its name; else ""
function get_key_source(label, scenesource)
    retval = ''

    if scenesource ~= nil then
        local scene_name = obs.obs_source_get_name(scenesource)
        print(label .. ' get_key_source for "' .. scene_name .. '"')

        local scene = obs.obs_scene_from_source(scenesource)
        local items = obs.obs_scene_enum_items(scene)
        for i, item in pairs(items) do
            local item_source = obs.obs_sceneitem_get_source(item)
            local item_name = obs.obs_source_get_name(item_source)
            -- print( '  ' .. label .. ' "' .. scene_name .. '" source "' .. item_name .. '"')
            if obs.obs_source_get_id(item_source) == "image_source" then
                ix,len = string.find(item_name, source_key)
                if ix == 1 then
                    print( '  ' .. label .. ' "' .. scene_name .. '" has "' .. item_name .. '"')
                    retval = item_name
                    break
                end
            end
        end
        obs.sceneitem_list_release(items)
    end

    return retval
end

-- Select a slide show.
-- Called after save or load, and for OBS_FRONTEND_EVENT_PREVIEW_SCENE_CHANGED,
-- which is also called on scene activation
function select_slideshow(label)
    print('select_slideshow ' .. label)

    -- no show active unless we find one
    local desired_source_name = ''

    local scenesource = obs.obs_frontend_get_current_scene()
    desired_source_name = get_key_source("Program", scenesource)
    obs.obs_source_release(scenesource)

    if desired_source_name == '' then
        -- Program has no slideshow, see if Preview does
        scenesource = obs.obs_frontend_get_current_preview_scene()
        desired_source_name = get_key_source("Preview", scenesource)
        obs.obs_source_release(scenesource)
    end

    if desired_source_name ~= '' then
        create_slideshow_if_needed(desired_source_name)
    end

    if active_source_name ~= desired_source_name then
        active_source_name = desired_source_name
        do_slide(label, 'SHOW_SLIDE')
    end
end

function do_slide(label, action)
    print('do_slide ' .. label .. ' action ' .. action)

    if active_source_name ~= '' then
        show = slide_shows[active_source_name]
        if not show then
            print('ERROR: no slideshow exists for "' .. active_source_name .. '"')
        else
            local source = obs.obs_get_source_by_name(active_source_name)
            if source then
                local current_slide = show['current_slide']
                local filenames     = show['filenames']

                if action == 'SHOW_SLIDE' then
                    -- no change to slide index
                elseif action == 'NEXT_SLIDE' then
                    if current_slide < #filenames then
                        current_slide = current_slide + 1
                    end
                elseif action == 'PREV_SLIDE' then
                    if current_slide > 1 then
                        current_slide = current_slide - 1
                    end
                elseif action == 'FIRST_SLIDE' then
                    current_slide = 1
                else
                    print('ERROR: invalid action ' .. action .. ' requested for "' .. active_source_name .. '"')
                end

                show['current_slide'] = current_slide
                local new_filename = filenames[current_slide]
                local current_filename = ''

                local nowSettings = obs.obs_source_get_settings(source)
                if not nowSettings then
                    print( "ERROR: Failed to get current settings for " .. active_source_name )
                else
                    current_filename = obs.obs_data_get_string(nowSettings, "file") 
                    obs.obs_data_release(nowSettings)
                    -- print( "Old file for " .. active_source_name .. ' is ' .. current_filename)
                end
                
                if new_filename and (new_filename ~= current_filename) then
                    local settings = obs.obs_data_create()
                    obs.obs_data_set_string(settings, "file", new_filename)
                    obs.obs_source_update(source, settings)
                    obs.obs_data_release(settings)

                    print( "File[" .. current_slide .. "] for " .. active_source_name .. ' is ' .. new_filename)
                end

                obs.obs_source_release(source)
            end
        end
    end
end

function reset_button_clicked(props, p)
    reset(true)
    return false
end

function next_button_clicked(props, p)
    next_slide(true)
    return false
end

function previous_button_clicked(props, p)
    previous_slide(true)
    return false
end

function reset(pressed)
    if pressed and (active_source_name ~= '') then
        -- Delete the current slideshow, to force a refresh of the file list
        print("Deleting slideshow for " .. active_source_name)
        slide_shows[active_source_name] = nil
        create_slideshow_if_needed(active_source_name)
    end
end

function next_slide(pressed)
    if pressed then
        do_slide('next_slide', 'NEXT_SLIDE')
    end
end

function previous_slide(pressed)
    if pressed then
        do_slide('prev_slide', 'PREV_SLIDE')
    end
end