local BiterHealthBooster = require 'modules.biter_health_booster'
local BiterRolls = require 'modules.wave_defense.biter_rolls'
local SideTargets = require 'modules.wave_defense.side_targets'
local ThreatEvent = require 'modules.wave_defense.threat_events'
local update_gui = require 'modules.wave_defense.gui'
local threat_values = require 'modules.wave_defense.threat_values'
local WD = require 'modules.wave_defense.table'
local Alert = require 'utils.alert'
local math_random = math.random
local math_floor = math.floor
local table_insert = table.insert
local math_sqrt = math.sqrt
local math_round = math.round
local Event = require 'utils.event'
local Public = {}

local group_size_modifier_raffle = {}
local group_size_chances = {
    {4, 0.4},
    {5, 0.5},
    {6, 0.6},
    {7, 0.7},
    {8, 0.8},
    {9, 0.9},
    {10, 1},
    {9, 1.1},
    {8, 1.2},
    {7, 1.3},
    {6, 1.4},
    {5, 1.5},
    {4, 1.6},
    {3, 1.7},
    {2, 1.8}
}
for _, v in pairs(group_size_chances) do
    for c = 1, v[1], 1 do
        table_insert(group_size_modifier_raffle, v[2])
    end
end
local group_size_modifier_raffle_size = #group_size_modifier_raffle

local function debug_print(msg)
    local debug = WD.get('debug')
    if not debug then
        return
    end
    print('WaveDefense: ' .. msg)
end

local function is_closer(pos1, pos2, pos)
    return ((pos1.x - pos.x) ^ 2 + (pos1.y - pos.y) ^ 2) < ((pos2.x - pos.x) ^ 2 + (pos2.y - pos.y) ^ 2)
end

local function shuffle_distance(tbl, position)
    local size = #tbl
    for i = size, 1, -1 do
        local rand = math_random(size)
        if is_closer(tbl[i].position, tbl[rand].position, position) and i > rand then
            tbl[i], tbl[rand] = tbl[rand], tbl[i]
        end
    end
    return tbl
end

local function fast_remove(tbl, index)
    local count = #tbl
    if index > count then
        return
    elseif index < count then
        tbl[index] = tbl[count]
    end

    tbl[count] = nil
end

local function remove_trees(entity)
    local surface = entity.surface
    local radius = 10
    local pos = entity.position
    local area = {{pos.x - radius, pos.y - radius}, {pos.x + radius, pos.y + radius}}
    local trees = surface.find_entities_filtered {area = area, type = 'tree'}
    if #trees > 0 then
        for i, tree in pairs(trees) do
            if tree and tree.valid then
                tree.destroy()
            end
        end
    end
end

local function remove_rocks(entity)
    local surface = entity.surface
    local radius = 10
    local pos = entity.position
    local area = {{pos.x - radius, pos.y - radius}, {pos.x + radius, pos.y + radius}}
    local rocks = surface.find_entities_filtered {area = area, type = 'simple-entity'}
    if #rocks > 0 then
        for i, rock in pairs(rocks) do
            if rock and rock.valid then
                rock.destroy()
            end
        end
    end
end
--[[
local function create_tiles(entity)
    local collapse
    local check_collapse_position = WD.get('check_collapse_position')
    if check_collapse_position and package.loaded['modules.collapse'] then
        collapse = require 'modules.collapse'.get_position()
    end
    local function get_replacement_tile(surface, position)
        for i = 1, 128, 1 do
            local vectors = {{0, i}, {0, i * -1}, {i, 0}, {i * -1, 0}}
            table.shuffle_table(vectors)
            for k, v in pairs(vectors) do
                local tile = surface.get_tile(position.x + v[1], position.y + v[2])
                if not tile.collides_with('resource-layer') then
                    return tile.name
                end
            end
        end
        return 'grass-1'
    end
    local surface = entity.surface
    local radius = 5
    local pos = entity.position
    local area = {{pos.x - radius, pos.y - radius}, {pos.x + radius, pos.y + radius}}
    local tile = surface.find_tiles_filtered {area = area, name = 'out-of-map'}
    if #tile > 0 then
        for i, t in pairs(tile) do
            if t and t.valid then
                if check_collapse_position and collapse then
                    if t.position.y <= collapse.y then
                        if t.position.x <= collapse.x then
                            surface.set_tiles(
                                {{name = get_replacement_tile(surface, t.position), position = t.position}},
                                true
                            )
                        end
                    end
                else
                    surface.set_tiles({{name = get_replacement_tile(surface, t.position), position = t.position}}, true)
                end
            end
        end
    end
end ]]
local function is_unit_valid(biter)
    local this = WD.get()
    if not biter.entity then
        debug_print('is_unit_valid - unit destroyed - does no longer exist')
        return false
    end
    if not biter.entity.valid then
        debug_print('is_unit_valid - unit destroyed - invalid')
        return false
    end
    if not biter.entity.unit_group then
        debug_print('is_unit_valid - unit destroyed - no unitgroup')
        return false
    end
    if biter.spawn_tick + this.max_biter_age < game.tick then
        debug_print('is_unit_valid - unit destroyed - timed out')
        return false
    end
    return true
end

local function refresh_active_unit_threat()
    local this = WD.get()
    debug_print('refresh_active_unit_threat - current value ' .. this.active_biter_threat)
    local active_biter_threat = 0
    for k, biter in pairs(this.active_biters) do
        if biter.entity then
            if biter.entity.valid then
                active_biter_threat = active_biter_threat + threat_values[biter.entity.name]
            end
        end
    end
    this.active_biter_threat = math_round(active_biter_threat * global.biter_health_boost, 2)
    debug_print('refresh_active_unit_threat - new value ' .. this.active_biter_threat)
end

local function time_out_biters()
    local this = WD.get()
    for k, biter in pairs(this.active_biters) do
        if not is_unit_valid(biter) then
            this.active_biter_count = this.active_biter_count - 1
            if biter.entity then
                if biter.entity.valid then
                    this.active_biter_threat =
                        this.active_biter_threat -
                        math_round(threat_values[biter.entity.name] * global.biter_health_boost, 2)
                    if biter.entity.force.index == 2 then
                        biter.entity.destroy()
                    end
                end
            end
            this.active_biters[k] = nil
        end
    end
end

local function get_random_close_spawner(surface)
    local this = WD.get()
    local spawners = surface.find_entities_filtered({type = 'unit-spawner', force = 'enemy'})
    if not spawners[1] then
        return false
    end
    local center = this.target.position
    local spawner = spawners[math_random(1, #spawners)]
    for i = 1, this.get_random_close_spawner_attempts, 1 do
        local spawner_2 = spawners[math_random(1, #spawners)]
        if
            (center.x - spawner_2.position.x) ^ 2 + (center.y - spawner_2.position.y) ^ 2 <
                (center.x - spawner.position.x) ^ 2 + (center.y - spawner.position.y) ^ 2
         then
            spawner = spawner_2
        end
    end
    debug_print('get_random_close_spawner - Found at x' .. spawner.position.x .. ' y' .. spawner.position.y)
    return spawner
end

local function get_random_character(this)
    local characters = {}
    for _, player in pairs(game.connected_players) do
        if player.character then
            if player.character.valid then
                if player.character.surface.index == this.surface_index then
                    characters[#characters + 1] = player.character
                end
            end
        end
    end
    if not characters[1] then
        return
    end
    return characters[math_random(1, #characters)]
end

local function set_main_target()
    local this = WD.get()
    if this.target then
        if this.target.valid then
            return
        end
    end

    local target = SideTargets.get_side_target()
    if not target then
        target = get_random_character(this)
    end
    if not target then
        return
    end

    this.target = target
    debug_print(
        'set_main_target -- New main target ' ..
            target.name .. ' at position x' .. target.position.x .. ' y' .. target.position.y .. ' selected.'
    )
end

local function set_group_spawn_position(surface)
    local this = WD.get()
    local spawner = get_random_close_spawner(surface)
    if not spawner then
        return
    end
    local position = surface.find_non_colliding_position('behemoth-biter', spawner.position, 64, 1)
    if not position then
        return
    end
    this.spawn_position = {x = position.x, y = position.y}
    debug_print(
        'set_group_spawn_position -- Changed position to x' ..
            this.spawn_position.x .. ' y' .. this.spawn_position.y .. '.'
    )
end

local function set_enemy_evolution()
    local this = WD.get()
    local evolution_factor = this.wave_number * 0.001
    local biter_health_boost = 1
    --local damage_increase = 0

    if evolution_factor > 1 then
        --damage_increase = damage_increase + (evolution_factor - 1)
        --biter_health_boost = biter_health_boost + (evolution_factor - 1) * 2
        evolution_factor = 1
    end

    if this.threat > 50000 then
        biter_health_boost = math_round(biter_health_boost + (this.threat - 50000) * 0.000033, 3)
    --damage_increase = math_round(damage_increase + this.threat * 0.0000025, 3)
    end

    global.biter_health_boost = biter_health_boost
    --game.forces.enemy.set_ammo_damage_modifier("melee", damage_increase)
    --game.forces.enemy.set_ammo_damage_modifier("biological", damage_increase)
    game.forces.enemy.evolution_factor = evolution_factor
end

local function can_units_spawn()
    local this = WD.get()
    if this.threat <= 0 then
        debug_print('can_units_spawn - threat too low')
        return false
    end
    if this.active_biter_count >= this.max_active_biters then
        debug_print('can_units_spawn - active biter count too high')
        return false
    end
    if this.active_biter_threat >= this.threat then
        debug_print('can_units_spawn - active biter threat too high (' .. this.active_biter_threat .. ')')
        return false
    end
    return true
end

local function get_active_unit_groups_count()
    local this = WD.get()
    local count = 0
    for _, g in pairs(this.unit_groups) do
        if g.valid then
            if #g.members > 0 then
                count = count + 1
            else
                g.destroy()
            end
        end
    end
    debug_print('Active unit group count: ' .. count)
    return count
end

local function spawn_biter(surface, is_boss_biter)
    local this = WD.get()
    if not is_boss_biter then
        if not can_units_spawn() then
            return
        end
    end

    local name
    if math_random(1, 100) > 73 then
        name = BiterRolls.wave_defense_roll_spitter_name()
    else
        name = BiterRolls.wave_defense_roll_biter_name()
    end
    local position = this.spawn_position

    local biter = surface.create_entity({name = name, position = position, force = 'enemy'})
    biter.ai_settings.allow_destroy_when_commands_fail = true
    biter.ai_settings.allow_try_return_to_spawner = false
    biter.ai_settings.do_separation = true
    if this.remove_entities then
        remove_trees(biter)
        remove_rocks(biter)
    end
    if is_boss_biter then
        BiterHealthBooster.add_boss_unit(biter, global.biter_health_boost * 5, 0.35)
    end
    this.active_biters[biter.unit_number] = {entity = biter, spawn_tick = game.tick}
    this.active_biter_count = this.active_biter_count + 1
    this.active_biter_threat = this.active_biter_threat + math_round(threat_values[name] * global.biter_health_boost, 2)
    return biter
end

local function set_next_wave()
    local this = WD.get()
    this.wave_number = this.wave_number + 1

    local threat_gain = this.wave_number * this.threat_gain_multiplier
    if this.wave_number > 1000 then
        threat_gain = threat_gain * (this.wave_number * 0.001)
    end
    if this.wave_number % 25 == 0 then
        this.boss_wave = true
        this.boss_wave_warning = true
        if this.alert_boss_wave then
            local msg = 'Boss Wave: ' .. this.wave_number
            local pos = {
                position = this.spawn_position
            }
            Alert.alert_all_players_location(pos, msg, {r = 0.8, g = 0.1, b = 0.1})
        end
        threat_gain = threat_gain * 2
    else
        if this.boss_wave_warning then
            this.boss_wave_warning = false
        end
    end

    this.threat = this.threat + math_floor(threat_gain)
    this.last_wave = this.next_wave
    this.next_wave = game.tick + this.wave_interval
    if this.clear_corpses then
        local surface = game.surfaces[this.surface_index]
        for _, entity in pairs(surface.find_entities_filtered {type = 'corpse'}) do
            if math_random(1, 2) == 1 then
                entity.destroy()
            end
        end
    end
end

local function reform_group(group)
    local this = WD.get()
    local group_position = {x = group.position.x, y = group.position.y}
    local step_length = this.unit_group_command_step_length
    local position = group.surface.find_non_colliding_position('biter-spawner', group_position, step_length, 4)
    if position then
        local new_group = group.surface.create_unit_group {position = position, force = group.force}
        for key, biter in pairs(group.members) do
            new_group.add_member(biter)
        end
        debug_print('Creating new unit group, because old one was stuck.')
        table_insert(this.unit_groups, new_group)
        return new_group
    else
        debug_print('Destroying stuck group.')
        --table.remove(this.unit_groups, group) --need group id instead to work, so as of now, groups are removed only by regular remove checks :( !
        group.destroy()
    end
    return nil
end

local function get_commmands(group)
    local this = WD.get()
    local commands = {}
    local group_position = {x = group.position.x, y = group.position.y}
    local step_length = this.unit_group_command_step_length

    if math_random(1, 2) == 1 then
        local side_target = SideTargets.get_side_target()
        if side_target then
            local target_position = side_target.position
            local distance_to_target =
                math_floor(
                math_sqrt((target_position.x - group_position.x) ^ 2 + (target_position.y - group_position.y) ^ 2)
            )
            local steps = math_floor(distance_to_target / step_length) + 1
            local vector = {
                math_round((target_position.x - group_position.x) / steps, 3),
                math_round((target_position.y - group_position.y) / steps, 3)
            }

            if this.debug then
                debug_print(
                    'get_commmands - to side_target x' .. side_target.position.x .. ' y' .. side_target.position.y
                )
                debug_print('get_commmands - distance_to_target:' .. distance_to_target .. ' steps:' .. steps)
                debug_print('get_commmands - vector ' .. vector[1] .. '_' .. vector[2])
            end

            for i = 1, steps, 1 do
                local old_position = group_position
                group_position.x = group_position.x + vector[1]
                group_position.y = group_position.y + vector[2]
                local obstacles =
                    group.surface.find_entities_filtered {
                    position = old_position,
                    radius = step_length,
                    type = {'simple-entity', 'tree'},
                    limit = 50
                }
                if obstacles then
                    shuffle_distance(obstacles, old_position)
                    for i = 1, #obstacles, 1 do
                        if obstacles[i].valid then
                            commands[#commands + 1] = {
                                type = defines.command.attack,
                                target = obstacles[i],
                                distraction = defines.distraction.by_enemy
                            }
                        end
                    end
                end
                local position =
                    group.surface.find_non_colliding_position('rocket-silo', group_position, step_length, 4)
                if position then
                    -- commands[#commands + 1] = {
                    -- 	type = defines.command.go_to_location,
                    -- 	destination = {x = position.x, y = position.y},
                    -- 	distraction = defines.distraction.by_anything
                    -- }
                    commands[#commands + 1] = {
                        type = defines.command.attack_area,
                        destination = {x = position.x, y = position.y},
                        radius = 16,
                        distraction = defines.distraction.by_anything
                    }
                else
                    local obstacles =
                        group.surface.find_entities_filtered {
                        position = group_position,
                        radius = step_length,
                        type = {'simple-entity', 'tree'},
                        limit = 50
                    }
                    if obstacles then
                        shuffle_distance(obstacles, old_position)
                        for i = 1, #obstacles, 1 do
                            if obstacles[i].valid then
                                commands[#commands + 1] = {
                                    type = defines.command.attack,
                                    target = obstacles[i],
                                    distraction = defines.distraction.by_enemy
                                }
                            end
                        end
                    end
                end
            end

            commands[#commands + 1] = {
                type = defines.command.attack,
                target = side_target,
                distraction = defines.distraction.by_enemy
            }
        end
    end

    local target_position = this.target.position
    local distance_to_target =
        math_floor(math_sqrt((target_position.x - group_position.x) ^ 2 + (target_position.y - group_position.y) ^ 2))
    local steps = math_floor(distance_to_target / step_length) + 1
    local vector = {
        math_round((target_position.x - group_position.x) / steps, 3),
        math_round((target_position.y - group_position.y) / steps, 3)
    }

    if this.debug then
        debug_print('get_commmands - to main target x' .. target_position.x .. ' y' .. target_position.y)
        debug_print('get_commmands - distance_to_target:' .. distance_to_target .. ' steps:' .. steps)
        debug_print('get_commmands - vector ' .. vector[1] .. '_' .. vector[2])
    end

    for i = 1, steps, 1 do
        local old_position = group_position
        group_position.x = group_position.x + vector[1]
        group_position.y = group_position.y + vector[2]
        local obstacles =
            group.surface.find_entities_filtered {
            position = old_position,
            radius = step_length / 2,
            type = {'simple-entity', 'tree'},
            limit = 50
        }
        if obstacles then
            shuffle_distance(obstacles, old_position)
            for i = 1, #obstacles, 1 do
                if obstacles[i].valid then
                    commands[#commands + 1] = {
                        type = defines.command.attack,
                        target = obstacles[i],
                        distraction = defines.distraction.by_enemy
                    }
                end
            end
        end
        local position = group.surface.find_non_colliding_position('rocket-silo', group_position, step_length, 1)
        if position then
            commands[#commands + 1] = {
                type = defines.command.attack_area,
                destination = {x = position.x, y = position.y},
                radius = 16,
                distraction = defines.distraction.by_anything
            }
        end
    end

    commands[#commands + 1] = {
        type = defines.command.attack_area,
        destination = {x = target_position.x, y = target_position.y},
        radius = 8,
        distraction = defines.distraction.by_enemy
    }

    commands[#commands + 1] = {
        type = defines.command.attack,
        target = this.target,
        distraction = defines.distraction.by_enemy
    }

    return commands
end

local function command_unit_group(group)
    local this = WD.get()
    if not this.unit_group_last_command[group.group_number] then
        this.unit_group_last_command[group.group_number] = game.tick - (this.unit_group_command_delay + 1)
    end
    if this.unit_group_last_command[group.group_number] then
        if this.unit_group_last_command[group.group_number] + this.unit_group_command_delay > game.tick then
            return
        end
    end
    local tile = group.surface.get_tile(group.position)
    if tile.valid and tile.collides_with('player-layer') then
        group = reform_group(group)
    end
    if not group then
        return
    end
    if not group.valid then
        return
    end
    group.set_command(
        {
            type = defines.command.compound,
            structure_type = defines.compound_command.return_last,
            commands = get_commmands(group)
        }
    )

    this.unit_group_last_command[group.group_number] = game.tick
end

local function give_commands_to_unit_groups()
    local this = WD.get()
    if #this.unit_groups == 0 then
        return
    end
    if not this.target then
        return
    end
    if not this.target.valid then
        return
    end
    for k, group in pairs(this.unit_groups) do
        if group.valid then
            command_unit_group(group, this)
        else
            fast_remove(this.unit_groups, k)
        end
    end
end

local function spawn_unit_group()
    local this = WD.get()
    if not can_units_spawn() then
        return
    end
    if not this.target then
        return
    end
    if not this.target.valid then
        return
    end
    if get_active_unit_groups_count() >= this.max_active_unit_groups then
        return
    end
    local surface = game.surfaces[this.surface_index]
    set_group_spawn_position(surface)
    local pos = this.spawn_position
    if not surface.can_place_entity({name = 'small-biter', position = pos}) then
        return
    end

    local radius = 10
    local area = {left_top = {pos.x - radius, pos.y - radius}, right_bottom = {pos.x + radius, pos.y + radius}}
    for k, v in pairs(surface.find_entities_filtered {area = area, name = 'land-mine'}) do
        if v and v.valid then
            v.die()
        end
    end

    BiterRolls.wave_defense_set_unit_raffle(this.wave_number)

    debug_print('Spawning unit group at x' .. this.spawn_position.x .. ' y' .. this.spawn_position.y)
    local position = this.spawn_position

    local unit_group = surface.create_unit_group({position = position, force = 'enemy'})
    local group_size =
        math_floor(
        this.average_unit_group_size * group_size_modifier_raffle[math_random(1, group_size_modifier_raffle_size)]
    )
    for _ = 1, group_size, 1 do
        local biter = spawn_biter(surface)
        if not biter then
            break
        end
        unit_group.add_member(biter)
    end

    if this.boss_wave then
        local count = math_random(1, math_floor(this.wave_number * 0.01) + 2)
        if count > 8 then
            count = 8
        end
        for _ = 1, count, 1 do
            local biter = spawn_biter(surface, true)
            if not biter then
                break
            end
            unit_group.add_member(biter)
        end
        this.boss_wave = false
    end

    table_insert(this.unit_groups, unit_group)
    return true
end

local function log_threat()
    local this = WD.get()
    this.threat_log_index = this.threat_log_index + 1
    this.threat_log[this.threat_log_index] = this.threat
    if this.threat_log_index > 900 then
        this.threat_log[this.threat_log_index - 901] = nil
    end
end

local function clear_tables()
    local this = WD.get()
    this.unit_group_last_command = {}
    for k, groups in next, this.active_biters do
        for _, entity in next, groups do
            if type(entity) == 'table' then
                if not entity or not entity.valid then
                    this.active_biters[k] = nil
                end
            end
        end
    end
end

local tick_tasks = {
    [30] = set_main_target,
    [60] = set_enemy_evolution,
    [90] = spawn_unit_group,
    [120] = give_commands_to_unit_groups,
    [150] = ThreatEvent.build_nest,
    [180] = ThreatEvent.build_worm,
    [3600] = time_out_biters,
    [7200] = refresh_active_unit_threat,
    [7400] = clear_tables
}

local function on_tick()
    local this = WD.get()
    if this.game_lost then
        return
    end

    if game.tick > this.next_wave then
        set_next_wave()
    end

    local t = game.tick % 300
    local t2 = game.tick % 18000

    if tick_tasks[t] then
        tick_tasks[t]()
    end
    if tick_tasks[t2] then
        tick_tasks[t2]()
    end

    if this.enable_threat_log then
        if game.tick % 60 == 0 then
            log_threat()
        end
    end
    for _, player in pairs(game.connected_players) do
        update_gui(player)
    end
end

Event.on_nth_tick(30, on_tick)

return Public