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-- mod-version:2 -- lite-xl 2.0
local subprocess = require "process"

local core = require "core"
local style = require "core.style"
local config = require "core.config"

--[[
    Example config (put it in user module):

    ```
    local fontconfig = require "plugins.fontconfig"
    fontconfig.use {
	font = { name = 'sans', size = 13 * SCALE },
	code_font = { name = 'monospace', size = 13 * SCALE },
    }
    ```

    if you want the fonts to load instantaneously on startup,
    you can try your luck on fontconfig.use_blocking. I won't be responsible for
    the slow startup time.
]]

local function resolve_font(spec)
    local scan_rate = 1 / config.fps
    local proc = subprocess.start({ "fc-match", "-s", "-f", "%{file}\n", spec }, {
        stdin = subprocess.REDIRECT_DISCARD,
        stdout = subprocess.REDIRECT_PIPE,
        stderr = subprocess.REDIRECT_STDOUT
    })
    local prev
    local lines = {}
    while proc:running() do
        coroutine.yield(scan_rate)
        local buf = proc:read_stdout()
	if type(buf) == "string" then
		local last_line_start = 1
		for line, ln in string.gmatch(buf, "([^\n]-)\n()") do
			last_line_start = ln
			if prev then line = prev .. line end
			table.insert(lines, line)
		end
		prev = last_line_start < #buf and string.sub(buf, last_line_start)
	end
    end
    if prev then table.insert(lines, prev) end

    if proc:returncode() ~= 0 or #lines < 1 then
        error(string.format("Cannot find a font matching the given specs: %q", spec), 0)
    end
    return lines[1]
end


local M = {}

function M.load(font_name, font_size, font_opt)
	local font_file = resolve_font(font_name)
	return renderer.font.load(font_file, font_size, font_opt)
end

function M.load_blocking(font_name, font_size, font_opt)
	local co = coroutine.create(function()
		return M.load(font_name, font_size, font_opt)
	end)
	local result
	while coroutine.status(co) ~= "dead" do
		local ok, err = coroutine.resume(co)
		if not ok then error(err) end
		result = err
	end
	return result
end

function M.use(spec)
	core.add_thread(function()
		for key, value in pairs(spec) do
			style[key] = M.load(value.name, value.size, value)
		end
	end)
end

-- there is basically no need for this, but for the sake of completeness
-- I'll leave this here
function M.use_blocking(spec)
	for key, value in pairs(spec) do
		style[key] = M.load_blocking(value.name, value.size, value)
	end
end

return M