--[[ Copyright (c) 2020 npc_strider
 * For direct use of code or graphics, credit is appreciated. See LICENSE.txt for more information.
 * This mod may contain modified code sourced from base/core Factorio
 * 
 * control.lua
 * Spiderbot.
--]]

require("util")

local function give_tool(player, stack)
    if player.clean_cursor() and player.cursor_stack.can_set_stack(stack) then
        if player.get_main_inventory() then
            player.get_main_inventory().remove("squad-spidertron-remote-sel")
            player.get_main_inventory().remove("squad-spidertron-remote")
        end
        player.cursor_stack.set_stack(stack)
        return true
    end
end

local function squad_center(spidersquad)
    local xbar=0
    local ybar=0
    local c=0
    for i=1, #spidersquad do
        local spider = spidersquad[i]
        c=c+1
        local pos = spider.position
        xbar=xbar+pos.x
        ybar=ybar+pos.y
    end
    return {xbar/c,ybar/c}
end

local function spiderbot_select(event)
    local index = event.player_index
    local spiders = event.entities
    if event.item == "squad-spidertron-remote-sel" and #spiders > 0 then
        local center = squad_center(spiders)
        global.spidercontrol_spidersquad[index] = {spiders={}} -- some future proofing here
        for i=1, #spiders do
            local spider = spiders[i]
            local pos = spider.position
            table.insert(global.spidercontrol_spidersquad[index].spiders, {
                spider_entity=spider,
                d={pos.x-center[1],pos.y-center[2]} -- dx and dy
            })
        end
        local player = game.players[index]
        if give_tool(player, {name="squad-spidertron-remote",count=1}) then
            player.cursor_stack.connected_entity=spiders[1]
        end
    end
end

local function validate_spiders(index)
    local c=0
    if global.spidercontrol_spidersquad[index] then
        --for i, spider_ in pairs(global.spidercontrol_spidersquad[index].spiders) do
        local d = global.spidercontrol_spidersquad[index].spiders
        for i=1, #d do
            if not d[i].spider_entity.valid then
                table.remove(global.spidercontrol_spidersquad[index].spiders,i)
                c=c+1
            end
        end
        if c > 0 then
            game.players[index].print(c .. " units were destroyed or mined since the last position command was sent")
        end
        return true
    end
end

local function spiderbot_designate(index, position)
    if validate_spiders(index) then
        local d_ = global.spidercontrol_spidersquad[index]
        local spidersquad = d_.spiders
        local leader = d_.spider_leader
        local l_d = {0,0}
        if leader then
            if spidersquad[leader].spider_entity.valid then
                -- game.players[index].print("Leader "..leader)
                l_d = spidersquad[leader].d
            else
                game.players[index].print("Leader destroyed") -- In case destroyed by biters/nuke/whatever
                global.spidercontrol_spidersquad[index].spider_leader = nil
                leader = nil
            end
        end


        local follow = game.players[index].is_shortcut_toggled("squad-spidertron-follow")
        for i=1, #spidersquad do
            if i ~= leader or not follow then
                local spider_ = spidersquad[i]
                local spider = spider_.spider_entity
                local d = spider_.d
                spider.autopilot_destination = {position.x+d[1]-l_d[1], position.y+d[2]-l_d[2]} -- leader dy and dx offsets so that the leader itself becomes the new mean of the squad.
            end
        end
    end
end

local function spiderbot_follow(player)
	if player.character then
		if player.is_shortcut_toggled("squad-spidertron-follow") then
			player.set_shortcut_toggled("squad-spidertron-follow", false)
        else
			player.set_shortcut_toggled("squad-spidertron-follow", true)
		end
	else
		player.print({"", {"error.error-message-box-title"}, ": ", {"player-doesnt-exist", {"gui.character"}}, " (", {"controller.god"}, "): ", {"gui-mod-info.status-disabled"}})
	end
end

local function initialize()
	if global.spidercontrol_spidersquad == nil then
		global.spidercontrol_spidersquad = {}
	end
end

script.on_init(initialize)
script.on_configuration_changed(initialize)
--commands.add_command("spiderbot_initialize_variables", "debug: ensure that all global tables are not nil (should not happen in a normal game)", initialize)

script.on_event(defines.events.on_player_alt_selected_area, spiderbot_select)
script.on_event(defines.events.on_player_selected_area, spiderbot_select)

script.on_event(defines.events.on_player_used_spider_remote, function(event)
    local index = event.player_index
    local player = game.players[index]
    local cursor_stack = player.cursor_stack
    if cursor_stack.valid_for_read and cursor_stack.name == "squad-spidertron-remote" and event.success then
        player.set_shortcut_toggled("squad-spidertron-follow", false)
        spiderbot_designate(index, event.position)
    elseif cursor_stack.valid_for_read and cursor_stack.name == "spidertron-remote" and event.success then -- WARNING: We're only overriding for the player's spidertron if it's the vanilla spidertron remote. Does not cover modded remotes!
        -- Alter dy and dx
        local unit_no = event.vehicle.unit_number
        local d_ = global.spidercontrol_spidersquad[index]
        local spidersquad = d_.spiders
        local leader = d_.spider_leader

        if spidersquad then -- HELLO: if you are reading this and have an idea how to optimize it pls let me know (Not really critical as it's not in the tick loop, but could be problematic for very large squads )
            for i=1, #spidersquad do  --something something premature debugging evil, but seriously the amount of loops are worrying (for large squds).
                if i ~= leader and spidersquad[i].spider_entity.unit_number == unit_no then -- Don't alter dy and dx for the squad leader (leads to infinite walking)
                    local dest = event.position
                    local flat = {} -- repack the array (which is divided because of us storing dy and dx) into a flat one
                    for j=1, #spidersquad do 
                        if j == i then
                            flat[#flat+1] = {position = dest}   -- need to predict where it will be and use that as a mean, not current location
                        else
                            flat[#flat+1] = spidersquad[j].spider_entity
                        end
                    end
                    local center = squad_center(flat)
                    -- tried to do something without calling this loop but it's the most reliable option

                    --very interesting problem : because the mean of the squad is dependent on the positions of each squad member, varying the dy/dx parameters of only one spider (originally the one we're moving) results in this one being scaled off the 'actual' target location - at very far distances from the squad mean this becomes very noticeable. This means we need to calculate the mean of the entire squad if one has changed position. I noticed this error because of the fact that the offset was not constant but proportional to distance away from the mean
                    for k=1, #spidersquad do
                        if k == i then
                            global.spidercontrol_spidersquad[index].spiders[k].d = {
                                dest.x - center[1], --dx
                                dest.y - center[2]  --dy
                            }
                        else
                            local pos = spidersquad[k].spider_entity.position
                            global.spidercontrol_spidersquad[index].spiders[k].d = {
                                pos.x - center[1], --dx
                                pos.y - center[2]  --dy
                            }
                        end
                    end
                    -- game.print("dx"..dest.x - center[1].."dy"..dest.y - center[2])
                    break
                end
            end
        end
    end
end)

local function squad_leader_state(index)
    local player = game.players[index]
    if player.vehicle and player.vehicle.type == "spider-vehicle" then
        local unit_no = player.vehicle.unit_number
        local d = global.spidercontrol_spidersquad[index].spiders
        if d then
            for i=1, #d do
                -- game.print(d[i].spider_entity.unit_number)
                if d[i].spider_entity.unit_number == unit_no then
                    global.spidercontrol_spidersquad[index].spider_leader = i
                    break
                end
            end
        end
    elseif player.vehicle == nil then
        global.spidercontrol_spidersquad[index].spider_leader = nil
    end
end

script.on_event(defines.events.on_player_driving_changed_state, function (event)
    squad_leader_state(event.player_index)
end)

script.on_event(defines.events.on_lua_shortcut, function (event)
    if event.prototype_name == "squad-spidertron-follow" then
        local index = event.player_index
        squad_leader_state(index)
        spiderbot_follow(game.players[index])
    end
end)

script.on_event(defines.events.on_player_created, function (event)
    global.spidercontrol_spidersquad[event.player_index] = {spiders={}}
end)

script.on_event("squad-spidertron-remote", function(event)
    give_tool(game.players[event.player_index], {name="squad-spidertron-remote-sel",count=1})
end)

script.on_event("squad-spidertron-follow", function(event)
    squad_leader_state(event.player_index)
    spiderbot_follow(game.players[event.player_index])
end)

script.on_event("squad-spidertron-switch-modes", function(event)
    local player = game.players[event.player_index]
    local cursor_stack = player.cursor_stack
    if cursor_stack.valid_for_read then
        if cursor_stack.name == "squad-spidertron-remote" then
            give_tool(player, {name="squad-spidertron-remote-sel",count=1})
        elseif cursor_stack.name == "squad-spidertron-remote-sel" then
            local e = global.spidercontrol_spidersquad[event.player_index]
            if e.spiders and e.spiders[1].spider_entity.valid and give_tool(player, {name="squad-spidertron-remote",count=1}) then
                player.cursor_stack.connected_entity=e.spiders[1].spider_entity
            end
        end
    end
end)


local mov_offset = settings.global["spidertron-follow-prediction-distance"].value --This is so the player stays within the spider squad when moving
local mov_offset_diagonal = math.sqrt(mov_offset^2/2)

local function pos_offset(position,dir)
    local def_dir = defines.direction
    local pos_x = position.x
    local pos_y = position.y

    if dir == def_dir.north then
        pos_y = pos_y - mov_offset
    elseif dir == def_dir.northeast then
        -- game.print("ne")
        pos_x = pos_x + mov_offset_diagonal
        pos_y = pos_y - mov_offset_diagonal
    elseif dir == def_dir.east then
        -- game.print("e")
        pos_x = pos_x + mov_offset
    elseif dir == def_dir.southeast then
        -- game.print("se")
        pos_x = pos_x + mov_offset_diagonal
        pos_y = pos_y + mov_offset_diagonal
    elseif dir == def_dir.south then
        -- game.print("s")
        pos_y = pos_y + mov_offset
    elseif dir == def_dir.southwest then
        -- game.print("sw")
        pos_x = pos_x - mov_offset_diagonal
        pos_y = pos_y + mov_offset_diagonal
    elseif dir == def_dir.west then
        -- game.print("w")
        pos_x = pos_x - mov_offset
    else -- northwest
        -- game.print("nw")
        pos_x = pos_x - mov_offset_diagonal
        pos_y = pos_y - mov_offset_diagonal
    end

    return {x=pos_x, y=pos_y}
end

local update_interval = settings.global["spidertron-follow-update-interval"].value

script.on_nth_tick(update_interval, function(event)
    for _, player in pairs(game.players) do
        if player.is_shortcut_toggled("squad-spidertron-follow") then
            local index = player.index
            if global.spidercontrol_spidersquad[index].spiders[1] then
                local p_pos = player.position
                local pos = p_pos
                if player.walking_state.walking then
                    local dir = player.walking_state.direction
                    pos = pos_offset(p_pos,dir)
                end
                spiderbot_designate(index, pos)
            end
        end
    end
end)