-- 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)
    local start_line_index  =  get_line_index(str, start_line)
    local end_line_index    =  get_line_index(str, end_line + 1)

    local matched_function  =  str:sub(start_line_index, end_line_index):match('function.+end')
    return matched_function
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

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

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

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

        local file = io.open(info.short_src, 'r')
        local function_str = get_full_function_str(file:read('*all'), info.linedefined, info.lastlinedefined)
        file:close()

        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] = '--]]'
    else
        -- 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: \''
            l[#l+1] = info.short_src
            l[#l+1] = '\' [Line'
            if info.linedefined == info.lastlinedefined then
                l[#l+1] = ': '
                l[#l+1] = tostring(info.linedefined)
            else
                l[#l+1] = 's: '
                l[#l+1] = tostring(info.linedefined)
                l[#l+1] = ' - '
                l[#l+1] = tostring(info.lastlinedefined)
            end
            l[#l+1] = ']'
        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

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