local utf8 = require("utf8")

require("coordinates")
-- to use with functions involving e
--local e = require("eulerNumber")

local function differential(x, y)
    return 2*y
end

local function loadWindow()
    love.window.setTitle("Slope Fields")
    love.keyboard.setKeyRepeat(true)
end
love.load = loadWindow

local function drawLine(line)
    love.graphics.setColor(unpack(line.color))
    love.graphics.line(line.p1.x, line.p1.y, line.p2.x, line.p2.y)
    love.graphics.circle("fill", line.midpoint.x, line.midpoint.y, 4)
end

local width, height = love.window.getMode()

local boxMargin = 10
local boxHeight = math.max(height / 12, 20)
local textbox = {
    x = boxMargin,
    y = height - (boxHeight + boxMargin),
    width = width - 2 * boxMargin,
    height = boxHeight,
    padding = 5,
    text = 'x',
    active = false,
    colors = {
        background = {0.2, 0.2, 0.2},
        text = {0.9, 0.9, 0.9}
    }
}
local graphbox = {
    x = boxMargin,
    y = boxMargin,
    width = width - 2 * boxMargin,
    height = textbox.y - 2 * boxMargin,
    colors = {
        background = {0.2, 0.2, 0.2}
    }
}

local center = {
    x = graphbox.x + graphbox.width / 2,
    y = graphbox.y + graphbox.height / 2
}
local scale = 5
local xScale, yScale
local step
if graphbox.width <= graphbox.height then
    step = graphbox.width / (2 * (scale+1))
    xScale = scale
    yScale = math.floor(graphbox.height / (2 * step)) - 1
else
    step = graphbox.height / (2 * (scale+1))
    yScale = scale
    xScale = math.floor(graphbox.width / (2 * step)) - 1
end

local lines = {
    grid = {},
    axes = {
        x = GetLineFromSlope(center, 0, graphbox.width),
        y = GetLineFromSlope(center, nil, graphbox.height)
    },
    field = {}
}
local xpos, ypos = graphbox.x, graphbox.y + graphbox.height
for y = -yScale, yScale, 1 do
    ypos = ypos - step
    lines.grid[{y=y}] = GetLineFromSlope({x = center.x, y = ypos}, 0, graphbox.width, {0.3, 0.3, 0.3})
end
for x = -xScale, xScale, 1 do
    xpos = xpos + step
    lines.grid[{x=x}] = GetLineFromSlope({x = xpos, y = center.y}, nil, graphbox.height, {0.3, 0.3, 0.3})
    ypos = graphbox.y + graphbox.height
    for y = -yScale, yScale, 1 do
        ypos = ypos - step
        lines.field[{x, y}] = GetLineFromSlope({x = xpos, y = ypos}, differential(x,y), 50, {0, 0.5, 1})
    end
end

local function func(x)
    return x^2
end
local points = GraphFunction(graphbox.x, graphbox.y, graphbox.width, graphbox.height, func)

local function drawScene()
    love.graphics.setColor(unpack(graphbox.colors.background))
    love.graphics.rectangle('fill',
        graphbox.x, graphbox.y,
        graphbox.width, graphbox.height,
        4, 4)

    love.graphics.setColor(unpack(textbox.colors.background))
    love.graphics.rectangle('fill',
        textbox.x, textbox.y,
        textbox.width, textbox.height,
        4, 4)

    love.graphics.setColor(unpack(textbox.colors.text))
    love.graphics.printf(textbox.text,
        textbox.x + textbox.padding, textbox.y + textbox.padding,
        textbox.width, 'left', 0, 2, 2)

    for _, line in pairs(lines.grid) do
        drawLine(line)
    end
    for _, line in pairs(lines.axes) do
        drawLine(line)
    end
    for _, line in pairs(lines.field) do
        drawLine(line)
    end

    if points ~= nil then
        love.graphics.setColor(0,1,0)
        love.graphics.points(points)
    end
end
love.draw = drawScene

local function textboxinput(text)
    if textbox.active and string.match(text,"[xy+%-%/*%^%d()]") then
        textbox.text = textbox.text .. text
    end
end
love.textinput = textboxinput

local function keypress(key)
    if key == "backspace" then
        local byteoffset = utf8.offset(textbox.text, -1)

        if byteoffset then
            textbox.text = string.sub(textbox.text, 1, byteoffset - 1)
        end
        return
    end
    if key == "return" then
        textbox.active = false
    end
end
love.keypressed = keypress

local function mousepress(x, y)
    if
        x >= textbox.x and
        x <= textbox.x + textbox.width and
        y >= textbox.y and
        y <= textbox.y + textbox.height
    then
        textbox.active = true
    elseif textbox.active then
        textbox.active = false
    end
end
love.mousepressed = mousepress