chapter_frame_only

# DOES NOT APPEND CHAPTERS CORRECTLY even if you delete chapter file after loading and resave
--[[
  * chapter_make_read.lua v.2022-06-24
  *
  * AUTHORS: dyphire
  * License: MIT
  * link: https://github.com/dyphire/mpv-scripts
--]]

-- This script also supports marks and creates external chapter files, usage:
-- Note: It can also be used to export the existing chapter information of the playing file.
-- add bindings to input.conf:
-- key script-message-to chapter_frame_only create_chapter
-- key script-message-to chapter_frame_only write_chapter

local msg = require 'mp.msg'
local utils = require 'mp.utils'
local options = require "mp.options"

local o = {
    -- Specifies the extension of the external chapter file.
    chapter_flie_ext = "_chapter.keyframe",
}

(require 'mp.options').read_options(o)


local function create_chapter()
    local time_pos = mp.get_property_number("time-pos")
    local frame_pos = mp.get_property_number("estimated-frame-number")
    local frame_pos_osd = mp.get_property_osd("estimated-frame-number")
    local curr_chapter = mp.get_property_number("chapter")
    local chapter_count = mp.get_property_number("chapter-list/count")
    local all_chapters = mp.get_property_native("chapter-list")
    mp.osd_message(frame_pos_osd, 1)

    if chapter_count == 0 then
        all_chapters[1] = {
            title = frame_pos .. "",
            time = time_pos
        }
        -- We just set it to zero here so when we add 1 later it ends up as 1
        -- otherwise it's probably "nil"
        curr_chapter = 0
        -- note that mpv will treat the beginning of the file as all_chapters[0] when using pageup/pagedown
        -- so we don't actually have to worry if the file doesn't start with a chapter
    else
        -- to insert a chapter we have to increase the index on all subsequent chapters
        -- otherwise we'll end up with duplicate chapter IDs which will confuse mpv
        -- +2 looks weird, but remember mpv indexes at 0 and lua indexes at 1
        -- adding two will turn "current chapter" from mpv notation into "next chapter" from lua's notation
        -- count down because these areas of memory overlap
        for i = chapter_count, curr_chapter + 2, -1 do
            all_chapters[i + 1] = all_chapters[i]
        end
        all_chapters[curr_chapter+2] = {
            title = frame_pos .. "",
            time = time_pos
        }
    end
    mp.set_property_native("chapter-list", all_chapters)
    mp.set_property_number("chapter", curr_chapter+1)
end


local function write_chapter()
    local euid = mp.get_property_number("estimated-frame-count")
    local chapter_count = mp.get_property_number("chapter-list/count")
    local all_chapters = mp.get_property_native("chapter-list")
    local insert_chapters = ""
    local curr = nil

    for i = 1, chapter_count, 1 do
        curr = all_chapters[i]
        local next_chapter = curr.title .. "\n"
        insert_chapters = insert_chapters .. next_chapter
    end

    local chapters = insert_chapters

    local path = mp.get_property("path")
    dir, name_ext = utils.split_path(path)
    local name = string.sub(name_ext, 1, (string.len(name_ext)-4))
    local out_path = utils.join_path(dir, name .. o.chapter_flie_ext)
    local file = io.open(out_path, "w")
    if file == nil then
        dir = utils.getcwd()
        out_path = utils.join_path(dir, "create" .. o.chapter_flie_ext)
        file = io.open(out_path, "w")
    end
    if file == nil then
        mp.error("Could not open chapter file for writing.")
        return
    end
    file:write(chapters)
    file:close()
    mp.osd_message("Export file to: " .. out_path, 3)
end


mp.register_script_message("create_chapter", create_chapter, {repeatable=true})
mp.register_script_message("write_chapter", write_chapter, {repeatable=false})