REAPER - Open UST corresponding to the active take of the selected media item.lua

-- * Header
-- Author: Kisaragi Hiu
-- Date: 2022-03-17T02:54:44+0900
-- License: The Unlicense (<https://unlicense.org/>). Full text below:
--
-- This is free and unencumbered software released into the public domain.
--
-- Anyone is free to copy, modify, publish, use, compile, sell, or
-- distribute this software, either in source code form or as a compiled
-- binary, for any purpose, commercial or non-commercial, and by any
-- means.
--
-- In jurisdictions that recognize copyright laws, the author or authors
-- of this software dedicate any and all copyright interest in the
-- software to the public domain. We make this dedication for the benefit
-- of the public at large and to the detriment of our heirs and
-- successors. We intend this dedication to be an overt act of
-- relinquishment in perpetuity of all present and future rights to this
-- software under copyright law.
--
-- THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
-- EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
-- MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
-- IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
-- OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
-- ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
-- OTHER DEALINGS IN THE SOFTWARE.
--
-- For more information, please refer to <http://unlicense.org/>

-- * Library functions

-- From
-- https://github.com/moteus/lua-path/blob/5a32c705/lua/path.lua#L147
function splitext(P)
    local s1, s2 = string.match(P, "(.-[^\\/.])(%.[^\\/.]*)$")
    if s1 then
        return s1, s2
    end
    return P, ""
end

-- From
-- https://github.com/moteus/lua-path/blob/5a32c705/lua/path.lua#L153
function splitpath(P)
    return string.match(P, "^(.-)[\\/]?([^\\/]*)$")
end

-- Modified from
-- https://github.com/moteus/lua-path/blob/5a32c705/lua/path.lua#L134
--
-- No, I have zero idea what select('#') or #var means
if reaper.GetOS():match("^Win") then
    PATH_SEPARATOR = "\\"
else
    PATH_SEPARATOR = "/"
end
function joinpaths(...)
    local t, n = {...}, select("#", ...)
    local r = t[1]
    for i = 2, #t do
        r = r .. PATH_SEPARATOR .. t[i]
    end
    return r
end

-- * Main function

function main()
    local selected_item = reaper.GetSelectedMediaItem(0, 0)
    local active_take = reaper.GetActiveTake(selected_item)
    local source = reaper.GetMediaItemTake_Source(active_take)
    local source_path = reaper.GetMediaSourceFileName(source)

    local source_dir, filename = splitpath(source_path)
    local base = splitext(filename)

    local cand = {}
    -- Intention: root/abc.wav -> root/abc.ust
    cand[1] = joinpaths(source_dir, base .. ".ust")
    -- Intention: root/abc.wav -> root/ust/abc.ust
    cand[2] = joinpaths(source_dir, "ust", base .. ".ust")
    -- Intention: root/wav/abc.wav -> root/ust/abc.ust
    cand[3] = joinpaths(source_dir, "..", "ust", base .. ".ust")

    local ret
    -- ret = reaper.file_exists(source_dir .. cdr)
    for _, path in next, cand do
        if reaper.file_exists(path) then
            ret = path
            break
        end
    end

    local OS = reaper.GetOS()
    local command

    if OS:match("^Win") then
        command = "start"
    elseif OS:match("^macOS") or OS:match("^OSX") then
        command = "open"
    elseif OS:match("^Other") then
        command = "xdg-open"
    end
    if ret then
        os.execute(command .. " " .. '"' .. ret .. '"')
    end
end

-- * Call it

main()

-- Local Variables:
-- eval: (if (commandp #'outshine-mode) (outshine-mode) (outline-minor-mode))
-- End: