-- Import

local LIBRARY
do
	local thispath = ... and select('1', ...):match('.+%.') or ''
	local was_loaded, library  =  pcall(require, thispath..'library')
    LIBRARY  =  was_loaded and library or {}
end

-- Constants


--------------------------------------------------------------------------------
-- Util

local function get_function_info (f)
    -- NOTE: Works best in LuaJIT or Lua 5.2+

    -- Regarding get-info:
    -- *  No need to includ 'f'. Function is already known
    -- *  No need to include 'L' (active lines) option. Ignored
    -- *  No need to include 'n' (name and namewhat). Won't work.
    local info = debug.getinfo(f, 'Su')
          info.params = {}
          info.ups = {}
          info.env = debug.getfenv and debug.getfenv(f)
          info.builtin = info.source == '=[C]'
    for i = 1, info.nparams or 0 do  info.params[i] = debug.getlocal(f, i)  end
    if info.isvararg or not info.nparams then  info.params[#info.params+1] = '...'  end
    -- Get upvalues
    for i = 1, info.nups do
        local k, v = debug.getupvalue(f, i)
        if k == '_ENV' and not debug.getfenv then
            info.env = v
        else
            info.ups[k] = v
        end
    end

    if     info.source:sub(1,1) == '=' then  info.defined_how = 'C'
    elseif info.source:sub(1,1) == '@' then  info.defined_how = 'file'
    else                                     info.defined_how = 'string'
    end

    if info.builtin and LIBRARY[f] then
        info.name       = LIBRARY[f].name
        info.params[1]  = LIBRARY[f].para
        info.doc        = LIBRARY[f].docs
    end

    return info
end

local function get_line_index (str, line_nr)
    local index = 0
    for _ = 2, line_nr do
        index = str:find('\n', index, true)
        if not index then  return #str  end
        index = index + 1
    end
    return index
end

local function get_full_function_str (str, start_line, end_line)
	-- Will attempt to find a string which refer to a function starting on
	-- line `start_line` and ending on line `end_line`.
    local start_line_index  =  get_line_index(str, start_line)
    local end_line_index    =  get_line_index(str, end_line + 1)

    local function_body  =  str:sub(start_line_index, end_line_index):match('function%s*[a-zA-Z0-9_.]*%s*(.+)end')
    return 'function '..function_body..'end'
end

local function get_function_str_from_file (filename, start_line, end_line)
	local file = io.open(filename, 'r')
	local str = file:read('*all')
	file:close()
	return get_full_function_str(str, start_line, end_line)
end

local function width_of_strings_in_l (l, start_i, end_i)
	-- FIXME: Copy of the one in pretty.lua
    local  width = 0
    for i = start_i or 1, (end_i or #l) do
        width = width + #l[i]
    end
    return width
end

--------------------------------------------------------------------------------

local function format_function_with_closure (value, options, depth, l, format_value)
	local info = get_function_info(value)

	--assert(info.nups > 0)
	local function_str = nil
	if (info.defined_how == 'string') then
		function_str = get_full_function_str(info.source, info.linedefined, info.lastlinedefined)
	else
		function_str = get_function_str_from_file(info.short_src, info.linedefined, info.lastlinedefined)
	end

	if info.nups > 0 then l[#l+1] = '(function () ' end
	-- Upvalues
	for k, v in pairs(info.ups) do
		l[#l+1] = 'local '
		l[#l+1] = tostring(k)
		l[#l+1] = ' = '
		format_value(v, options, depth + 1, l)
		l[#l+1] = '; '
	end
	-- Return function
	if info.nups > 0 then l[#l+1] = 'return ' end
	l[#l+1] = function_str
	--
	if info.nups > 0 then l[#l+1] = ' end)()' end
end

return function (value, options, depth, l, format_value)
    local info = get_function_info(value)

	if options.include_closure then
		return format_function_with_closure(value, options, depth, l, format_value)
	end

    if info.defined_how == 'string' then
        -- Function was defined as a string.
        l[#l+1] = get_full_function_str(info.source, info.linedefined, info.lastlinedefined)
        return;
    end

    -- Include function modifier, and alignment info.
    l[#l+1] = info.builtin and 'builtin ' or ''
    l[#l+1] = { #l[#l], 'func_mod'}

    -- Build rest of function signature
    l[#l+1] = 'function ('
    local top_before = #l
    for _, param in ipairs(info.params) do  l[#l+1], l[#l+2] = param, ', '  end
    if l[#l] == ', ' then  l[#l] = nil  end
    l[#l+1] = ')'
    l[#l+1] = { width_of_strings_in_l(l, top_before), 'func_def' }

    -- Cleanup and finish
    if not options.more_function_info or depth ~= 0  then
        l[#l+1] = ' ... end'
		return;
    end

	-- More info! --

	-- Name
    if info.name then
        l[#l+1] = '\n'
        l[#l+1] = options.indent
        l[#l+1] = '-- '
        l[#l+1] = info.name
    end

    -- Doc
    if info.doc then
        for doc_line in info.doc:gmatch('[^\n]+') do
            l[#l+1] = '\n'
            l[#l+1] = options.indent
            l[#l+1] = '-- '

            l[#l+1] = doc_line
        end
    end

    -- source
    if not info.builtin then
        l[#l+1] = '\n'
        l[#l+1] = options.indent
        l[#l+1] = ('-- source_file: \'%s\' '):format(info.short_src)
        if info.linedefined == info.lastlinedefined then
			l[#l+1] = ('[Line: %i]'):format(info.linedefined)
        else
			l[#l+1] = ('[Lines: %i - %i]'):format(info.linedefined, info.lastlinedefined)
        end
    end

    -- upvalues
    if info.nups > 0 and not info.builtin then
        l[#l+1] = '\n'
        l[#l+1] = options.indent
        l[#l+1] = '-- up_values:   '
        format_value(info.ups, options, depth + 1, l)
    end

	if options._all_function_info then
        -- NOTE: This is for testing/debugging/experimentation purposes.

		local function_str = get_function_str_from_file(info.short_src, info.linedefined, info.lastlinedefined)

        l[#l+1] = '\n\t--[[ Function Body\n\t'
        l[#l+1] = function_str
        l[#l+1] = '\n\t--]]'

        l[#l+1] = '\n\t--[[\n\tNative repr:'
        l[#l+1] = tostring(value)
        l[#l+1] = '\n\t'
        format_value(info, options, depth + 1, l)
        l[#l+1] = '--]]'
    end

    l[#l+1] = '\n\n'
    l[#l+1] = options.indent
    l[#l+1] = '...\nend'
end