ComfyFactorio/maps/biter_battles_v2/spec_spy.lua

local Global = require 'utils.global'

local this = {
    -- map player <> force
    initialForce = {}
}

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

local function is_spying(player)
    return this.initialForce[player.index] ~= nil
end

local function switch_force(player, force)
    this.initialForce[player.index] = player.force
    player.force = force
end

local function spy_production(player, force)
    if is_spying(player) then
        return
    end
    switch_force(player, force)
    player.opened = defines.gui_type.production
end

local function spy_tech_tree(player, force)
    if is_spying(player) then
        return
    end
    switch_force(player, force)
    player.open_technology_gui()
end

local function restore_force(player)
    if not is_spying(player) then
        return
    end
    player.force = this.initialForce[player.index]
    this.initialForce[player.index] = nil
end

-- When a player clicks on a spying prod LuaGuiElement
local function spy_prod_handler(event)
    if not event.element.valid then
        return
    end
    local elementToForce = {
        ['spy-north-prod'] = 'north',
        ['spy-south-prod'] = 'south'
    }
    local force = elementToForce[event.element.name]
    if force then
        local player = game.players[event.player_index]
        spy_production(player, force)
    end
end

-- When a player clicks on a spying tech LuaGuiElement
local function spy_tech_handler(event)
    if not event.element.valid then
        return
    end
    local elementToForce = {
        ['spy-north-tech'] = 'north',
        ['spy-south-tech'] = 'south'
    }
    local force = elementToForce[event.element.name]
    if force then
        local player = game.players[event.player_index]
        spy_tech_tree(player, force)
    end
end

-- When a player closes the prod view while spying
local function close_prod_handler(event)
    if event.gui_type ~= defines.gui_type.production then
        return
    end
    local player = game.players[event.player_index]
    -- If the player was spying
    if is_spying(player) then
        restore_force(player)
    end
end

-- When a player closes the tech view while spying
local function close_tech_handler(event)
    if event.gui_type ~= defines.gui_type.research then
        return
    end
    local player = game.players[event.player_index]
    -- If the player was spying
    if is_spying(player) then
        restore_force(player)
    end
end

local Event = require 'utils.event'
Event.add(defines.events.on_gui_click, spy_prod_handler)
Event.add(defines.events.on_gui_click, spy_tech_handler)
Event.add(defines.events.on_gui_closed, close_prod_handler)
Event.add(defines.events.on_gui_closed, close_tech_handler)