------------------------------------------------------------------------------
-- Imports
------------------------------------------------------------------------------

local love = require 'love'
local game_states = require 'src.states'


------------------------------------------------------------------------------
-- Variables
------------------------------------------------------------------------------

Current_state = 1
Fade_in = 0.0
Fade_out = 1.0
Change_state = false


------------------------------------------------------------------------------
-- Game methods
------------------------------------------------------------------------------

local function lerp(a, b, t)
    -- Linear interpolation between two values a and b, by a t between 0.0 and 1.0
    return (a * t) + (b * (1.0 - t))
end


------------------------------------------------------------------------------
-- Game methods
------------------------------------------------------------------------------

function love.load()
    game_states[Current_state]:load()
end


function love.update(dt)
    local new_state = game_states[Current_state]:update(dt)

    -- If the game state changed then trigger a fade out.
    if new_state ~= Current_state and Fade_out >= 1.0 then
        Fade_out = 0.0
        Change_state = true
    end

    -- If there is a fade in going then update it.
    if Fade_in < 1.0 then
        Fade_in = Fade_in + (dt / 2)
    end

    -- If there is a fade out going then update it.
    if Fade_out < 1.0 then
        Fade_out = Fade_out + (dt / 2)
    end

    -- Update the game state.
    if game_states[new_state] == nil then
        -- If the new state doesn't exist then wait for the fade out to end and quit.
        if Fade_out >= 1.0 then
            game_states[Current_state]:unload(dt)
            love.event.quit()
        end
    else
        -- If the new state exists then unload it's data and set the new state.
        if Change_state and Fade_out >= 1.0 then
            game_states[Current_state]:unload(dt)
            Current_state = new_state
            game_states[Current_state]:load()
            Change_state = false
        end
    end
end


function love.draw()
    -- Reset the drawing color and clear the screen.
    love.graphics.clear()

    -- Render the current game state.
    game_states[Current_state]:draw()

    -- If there is a fade in going then render it.
    if Fade_in < 1.0 then
        love.graphics.setColor(0, 0, 0)
        love.graphics.circle('fill', -320, love.graphics.getHeight() / 2, lerp(0, 400 * 2, Fade_in))
        love.graphics.setColor()
    end

    -- If there is a fade out going then render it.
    if Fade_out < 1.0 then
        love.graphics.setColor(0, 0, 0)
        love.graphics.circle('fill', -320, love.graphics.getHeight() / 2, lerp(400 * 2, 0, Fade_out))
        love.graphics.setColor()
    end
end


function love.keypressed(key)
    -- Send events to the active game state if there is no fade active.
    if Fade_in >= 1.0 and Fade_out >= 1.0 then
        game_states[Current_state]:keypressed(key)
    end
end


function love.mousemoved(x, y)
    -- Send events to the active game state if there is no fade active.
    if Fade_in >= 1.0 and Fade_out >= 1.0 then
        game_states[Current_state]:mousemoved(x, y)
    end
end


function love.mousepressed(x, y, btn)
    -- Send events to the active game state if there is no fade active.
    if Fade_in >= 1.0 and Fade_out >= 1.0 then
        game_states[Current_state]:mousemoved(x, y, btn)
    end
end