local component = require("component")
local sides = require("sides")
local robot = require("robot")
local os = require("os")
local event = require("event")
-- local modem = component.modem    -- Disabled, no network functions yet in 2.0
local inv = component.inventory_controller

-- Settings --
local farmHeight = 18
local farmWidth = 18
-- -------- --

local function isOdd(number)
-- returns true if number is odd
    if number % 2 ~= 0 then
        return true
    elseif number %2 == 0 then
        return false
    end
end

local function findEmptySlot()
-- Returns first found empty slot from inventory beneath robot
    for slot = 1, inv.getInventorySize(sides.down) do
        if inv.getStackInSlot(sides.down, slot) == nil then
            return slot
        end
    end
end

local function cutPlant()
    robot.select(1)     --  Select inventory slot 1, containing seeds
    robot.swingDown()   --  Harvest plant beneath robot
    inv.equip()         --  Equip seeds
    robot.useDown()     --  Plant seeds
    inv.equip()         --  Equip nothing, placing seeds back into slot 1
end

local function checkChest()
-- Returns true if chest has any empty slots
-- Currently unused function
    local isFull = findEmptySlot()
    if isFull == nil then
        return false
    else
        return true
    end
end

local function doColumn()
--  Rules   --
--  The bottom-left tilled soil block is 1,1
--  The charger is at 1,0
--  This function shall be started at x,1 and run to x,farmHeight
--  Another function after shall handle moving to next column
    local yval = 1
    while yval < farmHeight do
        cutPlant()
        robot.forward() -- Forward at the end of the function means
        yval = yval + 1 -- we must use lesser-than farmHeight
    end
    cutPlant()
end

local function nextColumn(xNumber)
--  Given the column number, determine how to move to the next column
--  On odd numbered columns, robot is facing y-pos and must move right
--  On even numbered columns, robot is facing y-neg and must move left
    if isOdd(xNumber) == true then
        robot.turnRight()
        robot.forward()
        robot.turnRight()
    elseif isOdd(xNumber) == false then
        robot.turnLeft()
        robot.forward()
        robot.turnLeft()
    end
    xNumber = xNumber + 1
    return xNumber
end

local function emptyInv()
-- Empty inventory into chest below robot
    local size = robot.inventorySize()
    local chestSize = inv.getInventorySize(sides.down)
    for i = 2, size do
        robot.select(i)
        local invCount = robot.count()
        local slot = findEmptySlot()
        if invCount ~= 0 and slot ~= nil then
            inv.dropIntoSlot(sides.down, slot)
        elseif slot == nil then
            print("Error! Deposit chest is full! Shutting down...")
            os.exit()   -- Abort program is chest is full
        end
    end
end

local function backToCharger()
--  Check whether farmWidth is odd or even and decide which way
--  the robot must move based upon that, same as nextColumn()
    if isOdd(farmWidth) == true then
        robot.turnLeft()
        for i = farmWidth-1, 1, -1 do
            robot.forward()
        end
        robot.turnLeft()
        for i = farmHeight-1, 0, -1 do -- Going to 1,0 for charger
            robot.forward()
        end
        robot.turnAround()  -- Turn around so we face the right direction
    elseif isOdd(farmWidth) == false then
        robot.turnRight()
        for i = farmWidth-1, 1, -1 do   -- Starting from farmWidth, 1
            robot.forward()             -- going to 1,1
        end
        robot.turnLeft()                -- Facing 1,0
        robot.forward()                 -- Moving to 1,0
        robot.turnAround()              -- Facing the right direction
    end
end

while true do
    robot.forward() -- Move off of charger at 1,0 to first farm block 1,1
    local xNumber = 1       -- Set column to 1
    while xNumber < farmWidth do
        doColumn()
        xNumber = nextColumn(xNumber)   -- Used less-than so we can do this at the end
    end
    if xNumber == farmWidth then
        doColumn()
        backToCharger()
    end
    robot.up()
    robot.back()
    emptyInv()
    robot.forward()
    robot.down()
end