-- by mewmew
-- modified by Gerkiz

local Event = require 'utils.event'
local Global = require 'utils.global'

local traps = {}

Global.register(
    traps,
    function(t)
        traps = t
    end
)

local function create_particles(surface, position, amount)
    if not surface.valid then
        return
    end
    local math_random = math.random
    for i = 1, amount, 1 do
        local m = math_random(6, 12)
        local m2 = m * 0.005

        surface.create_particle(
            {
                name = 'stone-particle',
                position = position,
                frame_speed = 0.1,
                vertical_speed = 0.1,
                height = 0.1,
                movement = {m2 - (math_random(0, m) * 0.01), m2 - (math_random(0, m) * 0.01)}
            }
        )
    end
end

local function spawn_biter(surface, position, evolution)
    if not surface.valid then
        return
    end
    local evo = math.floor(evolution * 1000)

    local biter_chances = {
        {name = 'small-biter', chance = math.floor(1000 - (evo * 1.6))},
        {name = 'small-spitter', chance = math.floor(500 - evo * 0.8)},
        {name = 'medium-biter', chance = -150 + evo},
        {name = 'medium-spitter', chance = -75 + math.floor(evo * 0.5)},
        {name = 'big-biter', chance = math.floor((evo - 500) * 3)},
        {name = 'big-spitter', chance = math.floor((evo - 500) * 2)},
        {name = 'behemoth-biter', chance = math.floor((evo - 800) * 6)},
        {name = 'behemoth-spitter', chance = math.floor((evo - 800) * 4)}
    }

    local max_chance = 0
    for i = 1, 8, 1 do
        if biter_chances[i].chance < 0 then
            biter_chances[i].chance = 0
        end
        max_chance = max_chance + biter_chances[i].chance
    end
    local r = math.random(1, max_chance)
    local current_chance = 0
    for i = 1, 8, 1 do
        current_chance = current_chance + biter_chances[i].chance
        if r <= current_chance then
            local biter_name = biter_chances[i].name
            local p = surface.find_non_colliding_position(biter_name, position, 10, 1)
            if not p then
                return
            end
            surface.create_entity({name = biter_name, position = p, force = 'enemy'})
            return
        end
    end
end

local function unearthing_biters(surface, position, amount)
    if not surface then
        return
    end
    if not surface.valid then
        return
    end
    if not position then
        return
    end
    if not position.x then
        return
    end
    if not position.y then
        return
    end

    local evolution = game.forces.enemy.evolution_factor

    local ticks = amount * 30
    ticks = ticks + 90
    for t = 1, ticks, 1 do
        if not traps[game.tick + t] then
            traps[game.tick + t] = {}
        end

        traps[game.tick + t][#traps[game.tick + t] + 1] = {
            callback = 'create_particles',
            params = {surface, {x = position.x, y = position.y}, 4}
        }

        if t > 90 then
            if t % 30 == 29 then
                traps[game.tick + t][#traps[game.tick + t] + 1] = {
                    callback = 'spawn_biter',
                    params = {surface, {x = position.x, y = position.y}, evolution}
                }
            end
        end
    end
end

local function on_tick()
    if not traps[game.tick] then
        return
    end
    for _, token in pairs(traps[game.tick]) do
        local callback = token.callback
        local params = token.params
        if callback == 'create_particles' then
            create_particles(params[1], params[2], params[3])
        elseif callback == 'spawn_biter' then
            spawn_biter(params[1], params[2], params[3])
        end
    end
    traps[game.tick] = nil
end

Event.add(defines.events.on_tick, on_tick)

return unearthing_biters