local base = _G
local cjson = require "cjson.safe"
local glob = require "posix.glob"
local io = require("io")
local string = require("string")
local time = require "posix.time"
local unistd = require "posix.unistd"

local _M = {}
local _internal_ = {}
_internal_.setup = {}
_internal_.read = {}



-- ############# utils ###########

function _internal_.write_to_file(path, data)
    -- base.print(string.format("writing '%s' to '%s'", data, path))
    local f, err = io.open(path, "w")
    if not f then return nil, err end

    local ret, err = f:write(data)
    f:close()
    return ret, err
end

function _internal_.read_from_file(path)
    local f, err = io.open(path, "r")
    if not f then return nil, err end

    local data, err = f:read("*a")
    f:close()
    return data, err
end



-- ############# i2c ###########

function _M.i2c_bus_path(bus)
    return string.format("/sys/bus/i2c/devices/i2c-%d", bus)
end

function _M.i2c_device_name(bus, address)
    return string.format("%d-%04x", bus, address)
end

function _M.i2c_device_path(bus, address)
    return string.format("/sys/bus/i2c/devices/" .. _M.i2c_device_name(bus, address))
end

function _M.i2c_add_device(bus, address, name)
    return _internal_.write_to_file(_M.i2c_bus_path(bus) .. "/new_device", string.format("%s 0x%02x", name, address))
end

function _M.i2c_delete_device(bus, address)
    return _internal_.write_to_file(_M.i2c_bus_path(bus) .. "/delete_device", string.format("0x%02x", address))
end

function _M.i2c_get_bus_number_from_name(name)
    local bus_paths, glob_result = glob.glob("/sys/bus/i2c/devices/i2c-*", 0)
    if not bus_paths then
        if glob_result == glob.GLOB_NOMATCH then return {} end
        if glob_result == glob.GLOB_ABORTED then return nil, "glob(): aborted" end
        if glob_result == glob.GLOB_NOSPACE then return nil, "glob(): no space" end
        return nil, "glob(): unknown error"
    end

    for _, bus_path in base.pairs(bus_paths) do
        local num = string.match(bus_path, '/i2c%-(%d+)$')
        if not num then return nil, "unable to parse bus number from path: " .. bus_path end

        local contents, err = _internal_.read_from_file(bus_path .. "/name")
        if contents ~= nil and contents:gsub("%s+", "") == name then return num end
    end
    return nil, "unable to find i2c bus with name: " .. name
end

function _M.i2c_get_mux_channels(parent, address)
    local channel_paths, glob_result = glob.glob(_M.i2c_device_path(parent, address) .. "/channel-*", 0)
    if not channel_paths then
        if glob_result == glob.GLOB_NOMATCH then return {} end
        if glob_result == glob.GLOB_ABORTED then return nil, "glob(): aborted" end
        if glob_result == glob.GLOB_NOSPACE then return nil, "glob(): no space" end
        return nil, "glob(): unknown error"
    end

    local channels = {}
    for _, channel_path in base.pairs(channel_paths) do
        local channel = string.match(channel_path, '/channel%-(%d+)$')
        if not channel then return nil, "unable to parse channel number from path: " .. channel_path end

        local bus_path, err = unistd.readlink(channel_path)
        if not bus_path then return nil, err end
        local bus = string.match(bus_path, '/i2c%-(%d+)$')
        if not bus then return nil, "unable to parse bus number from path: " .. bus_path end

        channels[base.tonumber(channel)] = base.tonumber(bus)
    end
    return channels
end


function _M.i2c_add_devices_recursive(bus_num, bus_name, devices)
    if bus_num == nil then
        local err
        bus_num, err = _M.i2c_get_bus_number_from_name(bus_name)
        if bus_num == nil then return nil, err end
    end

    local num_sensors = 0
    local device
    for _, device in base.ipairs(devices) do
        local ret, err = _M.i2c_add_device(bus_num, device.address, device.type)
        if not ret then return nil, err end

        local setup_function = _internal_.setup[device.type]
        if setup_function ~= nil then
            time.nanosleep({tv_sec = 0, tv_nsec = 100000000})
            local ret, err = setup_function(bus_num, device.address)
            if ret == nil then return nil, err end
            num_sensors = num_sensors + ret
        end

        if device.channels then
            time.nanosleep({tv_sec = 0, tv_nsec = 100000000})
            local mux_channels, err = _M.i2c_get_mux_channels(bus_num, device.address)
            if not mux_channels then return nil, error end
            local channel
            for _, channel in base.ipairs(device.channels) do
                if not mux_channels[channel.number] then return nil, string.format("i2c-mux %s has no channel %d", _M.i2c_device_name(bus_num, device.address), channel.number) end
                local tmp, err = _M.i2c_add_devices_recursive(mux_channels[channel.number], nil, channel.devices)
                if ret == nil then return nil, err end
                num_sensors = num_sensors + tmp
            end
        end
    end

    return num_sensors
end

function _M.i2c_read_sensors_recursive(bus_num, bus_name, devices)
    local readings = {}
    if bus_num == nil then
        local err
        bus_num, err = _M.i2c_get_bus_number_from_name(bus_name)
        if bus_num == nil then return readings end
    end

    local device
    for _, device in base.ipairs(devices) do
        local name = device.name ~= nil and device.name or device.type .. "_" ..  _M.i2c_device_name(bus_num, device.address)
        local read_function = _internal_.read[device.type]
        if read_function ~= nil then
            local values, kind = read_function(bus_num, device.address)
            if values ~= nil then
                readings[name] = values
                readings[name]['_kind_'] = kind
            end
        end

        if device.channels then
            local mux_channels, err = _M.i2c_get_mux_channels(bus_num, device.address)
            if not mux_channels then return nil, error end
            local channel
            for _, channel in base.ipairs(device.channels) do
                if mux_channels[channel.number] then
                    local tmp, err = _M.i2c_read_sensors_recursive(mux_channels[channel.number], nil, channel.devices)
                    if tmp ~= nil then for k,v in base.pairs(tmp) do readings[k] = v end end
                end
            end
        end
    end

    return readings
end



-- ############# 1-wire ###########

function _M.w1_device_path(address)
    return string.format("/sys/bus/w1/devices/" .. address)
end

function _M.w1_device_family_and_serial(address)
    local family, serial = string.match(address, '^(%x+)%-(%x+)$')
    if not family then return nil, "unable to extract device family and serial from 1-wire address " .. address end
    return family, serial
end


function _M.w1_setup_devices(devices)
    local num_sensors = 0
    local device
    for _, device in base.ipairs(devices) do
        local family, _ = _M.w1_device_family_and_serial(device.address)
        if family ~= nil then
            local setup_function = _internal_.setup["w1-" .. family]
            if setup_function ~= nil then
                local tmp, err = setup_function(device.address)
                if tmp == nil then return nil, err end
                num_sensors = num_sensors + tmp
            end
        end
    end

    return num_sensors
end

function _M.w1_read_sensors(devices)
    local readings = {}
    local device
    for _, device in base.ipairs(devices) do
        local name = device.name ~= nil and device.name or device.address
        local family, _ = _M.w1_device_family_and_serial(device.address)
        if family ~= nil then
            local read_function = _internal_.read["w1-" .. family]
            if read_function ~= nil then
                local values, kind = read_function(device.address)
                if values ~= nil then
                    readings[name] = values
                    readings[name]['_kind_'] = kind
                end
            end
        end
    end

    return readings
end



-- ############# gpio ###########

function _M.gpio_pin_path(number)
    return string.format("/sys/class/gpio/gpio%d", number)
end

function _M.gpio_export_pin(number)
    return _internal_.write_to_file("/sys/class/gpio/export", string.format("%d", number))
end

function _M.gpio_unexport_pin(number)
    return _internal_.write_to_file("/sys/class/gpio/unexport", string.format("%d", number))
end

function _M.gpio_read_pin(number)
    local value, err = _internal_.read_from_file(_M.gpio_pin_path(number) .. "/value")
    if not value then return nil, err end
    return value:match( "^%s*(.-)%s*$" )
end


function _M.gpio_setup_pins(pins)
    local num_pins = 0
    local pin
    for _, pin in base.ipairs(pins) do
        local ret, err = _M.gpio_export_pin(pin.number)
        if ret == nil then return nil, err end
        num_pins = num_pins + 1
    end

    return num_pins
end

function _M.gpio_read_pins(pins)
    local readings = {}
    local pin
    for _, pin in base.ipairs(pins) do
        local name = pin.name ~= nil and pin.name or string.format("gpio-%d", pin.number)
        local value, err = _M.gpio_read_pin(pin.number)
        if value ~= nil then
            readings[name] = { gpio = value, _kind_ = 'gpio' }
        end
    end

    return readings
end



-- ############# iio ###########

function _M.iio_device_path_from_i2c_device(bus, address)
    local device_paths, glob_result = glob.glob(_M.i2c_device_path(bus, address) .. "/iio:device*", 0)
    if not device_paths then
        if glob_result == glob.GLOB_NOMATCH then return nil, "couldn't find iio device handle for i2c device " .. _M.i2c_device_name(bus, address) end
        if glob_result == glob.GLOB_ABORTED then return nil, "glob(): aborted" end
        if glob_result == glob.GLOB_NOSPACE then return nil, "glob(): no space" end
        return nil, "glob(): unknown error"
    end
    if #device_paths ~= 1 then return nil, "found more than one iio device for i2c device " .. _M.i2c_device_name(bus, address) end
    return device_paths[1]
end


function _M.iio_setup_bmp280(bus, address)
    local iio_device, err = _M.iio_device_path_from_i2c_device(bus, address)
    if not iio_device then return nil, err end

    local ret, err = _internal_.write_to_file(iio_device .. '/in_pressure_oversampling_ratio', '1')
    if not ret then return nil, err end
    local ret, err = _internal_.write_to_file(iio_device .. '/in_temp_oversampling_ratio', '1')
    if not ret then return nil, err end

    return 2
end
_internal_.setup['bmp280'] = _M.iio_setup_bmp280

function _M.iio_read_bmp280(bus, address)
    local iio_device, err = _M.iio_device_path_from_i2c_device(bus, address)
    if not iio_device then return end

    local values = {}
    local tmp, err = _internal_.read_from_file(iio_device .. '/in_pressure_input')
    if tmp ~= nil then
        local val = base.tonumber(tmp)
        if val ~= nil then values['pressure'] = val*1000 end
    end
    tmp, err = _internal_.read_from_file(iio_device .. '/in_temp_input')
    if tmp ~= nil then
        local val = base.tonumber(tmp)
        if val ~= nil then values['temperature'] = val/1000 end
    end

    return values, 'bmp280'
end
_internal_.read['bmp280'] = _M.iio_read_bmp280


function _M.iio_setup_bme280(bus, address)
    local iio_device, err = _M.iio_device_path_from_i2c_device(bus, address)
    if not iio_device then return nil, err end

    local ret, err = _internal_.write_to_file(iio_device .. '/in_humidityrelative_oversampling_ratio', '1')
    if not ret then return nil, err end
    local ret, err = _internal_.write_to_file(iio_device .. '/in_pressure_oversampling_ratio', '1')
    if not ret then return nil, err end
    local ret, err = _internal_.write_to_file(iio_device .. '/in_temp_oversampling_ratio', '1')
    if not ret then return nil, err end

    return 3
end
_internal_.setup['bme280'] = _M.iio_setup_bme280

function _M.iio_read_bme280(bus, address)
    local iio_device, err = _M.iio_device_path_from_i2c_device(bus, address)
    if not iio_device then return end

    local values = {}
    local tmp, err = _internal_.read_from_file(iio_device .. '/in_humidityrelative_input')
    if tmp ~= nil then
        local val = base.tonumber(tmp)
        if val ~= nil then values['humidity'] = val/1000 end
    end
    local tmp, err = _internal_.read_from_file(iio_device .. '/in_pressure_input')
    if tmp ~= nil then
        local val = base.tonumber(tmp)
        if val ~= nil then values['pressure'] = val*1000 end
    end
    tmp, err = _internal_.read_from_file(iio_device .. '/in_temp_input')
    if tmp ~= nil then
        local val = base.tonumber(tmp)
        if val ~= nil then values['temperature'] = val/1000 end
    end

    return values, 'bme280'
end
_internal_.read['bme280'] = _M.iio_read_bme280


function _M.iio_setup_am2315(bus, address)
    return 2
end
_internal_.setup['am2315'] = _M.iio_setup_am2315

function _M.iio_read_am2315(bus, address)
    local iio_device, err = _M.iio_device_path_from_i2c_device(bus, address)
    if not iio_device then return end

    local values = {}
    local tmp, err = _internal_.read_from_file(iio_device .. '/in_humidityrelative_raw')
    if tmp ~= nil then
        local val = base.tonumber(tmp)
        if val ~= nil then values['humidity'] = val/10  end
    end
    time.nanosleep({tv_sec = 0, tv_nsec = 100000000})
    tmp, err = _internal_.read_from_file(iio_device .. '/in_temp_raw')
    if tmp ~= nil then
        local val = base.tonumber(tmp)
        if val ~= nil then values['temperature'] = val/10 end
    end

    return values, 'am2315'
end
_internal_.read['am2315'] = _M.iio_read_am2315



-- ############# hwmon ###########

function _M.hwmon_device_path_from_w1_device(address)
    local device_paths, glob_result = glob.glob(_M.w1_device_path(address) .. "/hwmon/hwmon*", 0)
    if not device_paths then
        if glob_result == glob.GLOB_NOMATCH then return nil, "couldn't find hwmon device handle for 1-wire device " .. address end
        if glob_result == glob.GLOB_ABORTED then return nil, "glob(): aborted" end
        if glob_result == glob.GLOB_NOSPACE then return nil, "glob(): no space" end
        return nil, "glob(): unknown error"
    end
    if #device_paths ~= 1 then return nil, "found more than one hwmon device for 1-wire device " .. address end
    return device_paths[1]
end


function _M.hwmon_setup_w1_therm(address)
    return 1
end
_internal_.setup['w1-10'] = _M.hwmon_setup_w1_therm
_internal_.setup['w1-22'] = _M.hwmon_setup_w1_therm
_internal_.setup['w1-28'] = _M.hwmon_setup_w1_therm
_internal_.setup['w1-3B'] = _M.hwmon_setup_w1_therm
_internal_.setup['w1-42'] = _M.hwmon_setup_w1_therm

function _M.hwmon_read_w1_therm(address)
    local hwmon_device, err = _M.hwmon_device_path_from_w1_device(address)
    if not hwmon_device then return end

    local values = {}
    local tmp, err = _internal_.read_from_file(hwmon_device .. '/temp1_input')
    if tmp ~= nil then
        local val = base.tonumber(tmp)
        if val ~= nil then values['temperature'] = val/1000 end
    end

    return values
end
_internal_.read['w1-10'] = function(address) return _M.hwmon_read_w1_therm(address), "ds18s20" end
_internal_.read['w1-22'] = function(address) return _M.hwmon_read_w1_therm(address), "ds1822" end
_internal_.read['w1-28'] = function(address) return _M.hwmon_read_w1_therm(address), "ds18b20" end
_internal_.read['w1-3B'] = function(address) return _M.hwmon_read_w1_therm(address), "ds1825" end
_internal_.read['w1-42'] = function(address) return _M.hwmon_read_w1_therm(address), "ds28ea00" end



-- ############# high-level interface ###########

function _M.read_config(path)
    sensors_json, err = _internal_.read_from_file(path)
    if not sensors_json then return nil, err end

    return cjson.decode(sensors_json)
end

function _M.setup(config)
    local num_sensors = 0
    if config.i2c then
        local i2c_bus
        for _, i2c_bus in base.ipairs(config.i2c) do
            local tmp, err = _M.i2c_add_devices_recursive(i2c_bus.number, i2c_bus.name, i2c_bus.devices)
            if tmp == nil then return nil, err end
            num_sensors = num_sensors + tmp
        end
    end
    if config.w1 then
        local tmp, err = _M.w1_setup_devices(config.w1)
        if tmp == nil then return nil, err end
        num_sensors = num_sensors + tmp
    end
    if config.gpio then
        local tmp, err = _M.gpio_setup_pins(config.gpio)
        if tmp == nil then return nil, err end
        num_sensors = num_sensors + tmp
    end

    return num_sensors
end

function _M.read(config)
    local readings = {}
    if config.i2c then
        local i2c_bus
        for _, i2c_bus in base.ipairs(config.i2c) do
            local tmp, err = _M.i2c_read_sensors_recursive(i2c_bus.number, i2c_bus.name, i2c_bus.devices)
            if tmp ~= nil then for k,v in base.pairs(tmp) do readings[k] = v end end
        end
    end
    if config.w1 then
        local tmp, err = _M.w1_read_sensors(config.w1)
        if tmp ~= nil then for k,v in base.pairs(tmp) do readings[k] = v end end
    end
    if config.gpio then
        local tmp, err = _M.gpio_read_pins(config.gpio)
        if tmp ~= nil then for k,v in base.pairs(tmp) do readings[k] = v end end
    end

    return readings
end



-- ################################

return _M