-- ====================================================================================
-- TUM.AIRFORCE - HANDLES THE FRIENDLY AND ENEMY COMBAT AIR PATROL
-- ====================================================================================
-- ====================================================================================

TUM.airForce = {}

do
    local SUPPRESSION_INCREASE_ON_KILL = 0.35 -- Value added to enemyCAPSuppression each time an enemy aircraft is shot down

    local desiredUnitCount = { 4, 4 } -- Desired max number of aircraft in the air at any single time
    local fighterGroups = { {}, {} }

    local enemyCAPSuppression = 1
    local enemyCAPSuppressionTimer = 1
    local playerCenter = nil

    local function getSkillLevel(side)
        -- Friendly AI is always excellent
        if side == TUM.settings.getPlayerCoalition() then return "Excellent" end

        local airForceLevel = TUM.settings.getValue(TUM.settings.id.ENEMY_AIR_FORCE) - 1

        -- if airForceLevel <= 1 then return "Average"
        -- elseif airForceLevel == 2 then return DCSEx.table.getRandom({"Average", "Good"})
        -- elseif airForceLevel == 3 then return DCSEx.table.getRandom({"Good", "High"})
        -- else return DCSEx.table.getRandom({"High", "Excellent"})
        -- end

        if airForceLevel <= 2 then return "Average"
        elseif airForceLevel == 3 then return DCSEx.table.getRandom({"Average", "Good"})
        else return DCSEx.table.getRandom({"Good", "High", "Excellent"})
        end
    end

    local function randomizeDesiredAircraftCount(side)
        local airForceLevel = 0

        if side == TUM.settings.getPlayerCoalition() then
            if TUM.settings.getValue(TUM.settings.id.AI_CAP) == 1 then
                airForceLevel = 2
            else
                airForceLevel = 0
            end
        else
            airForceLevel = TUM.settings.getValue(TUM.settings.id.ENEMY_AIR_FORCE) - 1
        end

        if airForceLevel == 0 then
            desiredUnitCount[side] = 0
        else
            desiredUnitCount[side] = math.random(airForceLevel, math.ceil(airForceLevel * 1.5)) + 1
        end
    end

    local function getAirborneUnitCount(side)
        local count = 0

        for _,id in ipairs(fighterGroups[side]) do
            local g = DCSEx.world.getGroupByID(id)
            if g then
                count = count + g:getSize()
            end
        end

        return count
    end

    local function launchNewAircraftGroup(side, airbases)
        local groupSize = DCSEx.table.getRandom({ 1, 2, 2, 2, 2, 3, 3, 4 })
        groupSize = math.min(groupSize, desiredUnitCount[side] - getAirborneUnitCount(side))
        if groupSize <= 0 then return false end -- No aircraft slots left

        local faction = TUM.settings.getEnemyFaction()
        if side == TUM.settings.getPlayerCoalition() then faction = TUM.settings.getPlayerFaction() end

        local units = Library.factions.getUnits(faction, DCSEx.enums.unitFamily.PLANE_FIGHTER, groupSize, true)
        if not units or #units == 0 then return false end -- No aircraft found

        -- If enemy CAP suppression timer > 0, decrement it by 1 but don't spawn any aircraft
        if side == TUM.settings.getEnemyCoalition() then
            enemyCAPSuppressionTimer = enemyCAPSuppressionTimer - 1
            if enemyCAPSuppressionTimer > 0 then
                TUM.log("Enemy CAP is still suppressed (suppression="..tostring(enemyCAPSuppressionTimer).."), no enemy CAP spawned.")
                return false
            end

            enemyCAPSuppressionTimer = enemyCAPSuppression
        end

        local launchAirbase = airbases[DCSEx.math.clamp(math.random(1, math.ceil(math.sqrt(#airbases))), 1, #airbases)]
        local originPt = DCSEx.math.vec3ToVec2(launchAirbase:getPoint())

        local groupInfo = DCSEx.unitGroupMaker.create(
            side, Group.Category.AIRPLANE,
            originPt, units,
            {
                moveTo = DCSEx.math.randomPointInCircle(TUM.objectives.getCenter(), TUM.objectives.getRadius(), 0),
                silenced = true,
                skill = getSkillLevel(side),
                takeOff = true,
                taskCAP = true,
                unlimitedFuel = true
            })

        if not groupInfo then return false end
        table.insert(fighterGroups[side], groupInfo.groupID)

        local players = coalition.getPlayers(TUM.settings.getPlayerCoalition())

        if side == TUM.settings.getPlayerCoalition() then
            local newUnit = nil
            local newGroup = DCSEx.world.getGroupByID(groupInfo.groupID)
            if newGroup then newUnit = newGroup:getUnit(1) end

            local callsign = "FRIENDLY CAP"
            local typeName = "Fighter aircraft"
            if newUnit then
                callsign = newUnit:getCallsign()
                typeName = Library.objectNames.get(newUnit)
            end

            for _,p in ipairs(players) do
                local abInfo = launchAirbase:getName()
                abInfo = abInfo.." ("..DCSEx.dcs.getBRAA(launchAirbase:getPoint(), p:getPoint(), false, false, true).." from you)"

                TUM.radio.playForUnit(DCSEx.dcs.getObjectIDAsNumber(p), "pilotNewFriendlyAircraft", { typeName, abInfo }, callsign)
            end
        else
            for _,p in ipairs(players) do
                local abInfo = launchAirbase:getName()
                abInfo = abInfo.." ("..DCSEx.dcs.getBRAA(launchAirbase:getPoint(), p:getPoint(), false, false, true).." from you)"

                TUM.radio.playForUnit(DCSEx.dcs.getObjectIDAsNumber(p), "commandNewEnemyAircraft", { DCSEx.string.toStringNumber(groupSize), abInfo }, "Command")
            end
        end

        return true
    end

    local function updateAirForce(side)
        if desiredUnitCount[side] <= 0 then return false end -- No airforce
        if not TUM.DEBUG_MODE and #DCSEx.world.getPlayersInAir() == 0 then return false end -- No players currently in the air, don't spawn new AI aircraft (except in debug mode)

        local validAirbases = {}
        local airbases = coalition.getAirbases(side)
        for _,ab in pairs(airbases) do
            if ab:getDesc().category ~= Airbase.Category.SHIP then -- Ignore ships
                table.insert(validAirbases, ab)
            end
        end
        if not validAirbases or #validAirbases == 0 then return false end -- No airbases found for this coalition, nowhere to take off from

        if side == TUM.settings.getPlayerCoalition() then
            validAirbases = { DCSEx.dcs.getNearestObject(playerCenter, validAirbases) }
        else
            validAirbases = DCSEx.dcs.getNearestObjects(TUM.objectives.getCenter(), validAirbases)
        end

        local airborneUnitCount = getAirborneUnitCount(side)

        if airborneUnitCount < desiredUnitCount[side] then
            if math.random(1, 2 + math.ceil(airborneUnitCount / 2)) == 1 then
                if math.random(1, 4) then
                    randomizeDesiredAircraftCount(side)
                end

                return launchNewAircraftGroup(side, validAirbases)
            end
        end

        return false
    end

    ----------------------------------------------------------
    -- Called on every mission update tick (every 10-20 seconds)
    -- @param side The side for which air force must be updated
    -- @return True if something was done this tick, false otherwise
    ----------------------------------------------------------    
    function TUM.airForce.onClockTick(side)
        if TUM.mission.getStatus() == TUM.mission.status.NONE then return false end -- Not currenly in a mission
        if TUM.objectives.getCount() <= 0 then return false end -- No objectives, nothing to defend for CAP

        return updateAirForce(side)
    end

    -------------------------------------
    -- Called when an event is raised
    -- @param event The DCS World event
    -------------------------------------
    function TUM.airForce.onEvent(event)
        if not event.initiator then return end
        if Object.getCategory(event.initiator) ~= Object.Category.UNIT then return end
        if event.id ~= world.event.S_EVENT_UNIT_LOST then return end

        local groupID = DCSEx.dcs.getGroupIDAsNumber(event.initiator:getGroup())

        if DCSEx.table.contains(fighterGroups[TUM.settings.getEnemyCoalition()], groupID) then
            enemyCAPSuppression = enemyCAPSuppression + SUPPRESSION_INCREASE_ON_KILL
            TUM.log("Enemy CAP suppression increased to "..tostring(enemyCAPSuppression))
        end
    end

    function TUM.airForce.create()
        TUM.airForce.removeAll()
        TUM.log("Creating friendly and enemy air forces...")

        for side=1,2 do
            randomizeDesiredAircraftCount(side)
        end
    end

    function TUM.airForce.removeAll()
        if #fighterGroups[1] > 0 or #fighterGroups[2] > 0 then
            TUM.log("Removing all friendly and enemy air force...")
        end

        for side=1,2 do
            for _,id in ipairs(fighterGroups[side]) do
                DCSEx.world.destroyGroupByID(id)
            end
        end

        -- Reset enemy CAP suppression
        enemyCAPSuppression = 1
        enemyCAPSuppressionTimer = 1

        fighterGroups = { {}, {} }
    end

    function TUM.airForce.onStartUp()
        playerCenter = DCSEx.envMission.getPlayerGroupsCenterPoint()
        if not playerCenter then
            playerCenter = { x = env.mission.map.centerX, y = env.mission.map.centerY }
        end

        -- TODO: build list of airbases now instead of of each update() (but what about destroyed airbases?)

        return true
    end
end