--- **Functional** -- Make SAM sites execute evasive and defensive behaviour when being fired upon.
--
-- ===
--
-- ## Features:
--
--   * When SAM sites are being fired upon, the SAMs will take evasive action will reposition themselves when possible.
--   * When SAM sites are being fired upon, the SAMs will take defensive action by shutting down their radars.
--
-- ===
--
-- ## Missions:
--
-- [SEV - SEAD Evasion](https://github.com/FlightControl-Master/MOOSE_MISSIONS/tree/master/SEV%20-%20SEAD%20Evasion)
--
-- ===
--
-- ### Authors: **FlightControl**, **applevangelist**
--
-- Last Update: Nov 2021
--
-- ===
--
-- @module Functional.Sead
-- @image SEAD.JPG

---
-- @type SEAD
-- @extends Core.Base#BASE

--- Make SAM sites execute evasive and defensive behaviour when being fired upon.
--
-- This class is very easy to use. Just setup a SEAD object by using @{#SEAD.New}() and SAMs will evade and take defensive action when being fired upon.
--
-- # Constructor:
--
-- Use the @{#SEAD.New}() constructor to create a new SEAD object.
--
--       SEAD_RU_SAM_Defenses = SEAD:New( { 'RU SA-6 Kub', 'RU SA-6 Defenses', 'RU MI-26 Troops', 'RU Attack Gori' } )
--
-- @field #SEAD
SEAD = {
  ClassName = "SEAD",
  TargetSkill = {
    Average   = { Evade = 30, DelayOn = { 40, 60 } } ,
    Good      = { Evade = 20, DelayOn = { 30, 50 } } ,
    High      = { Evade = 15, DelayOn = { 20, 40 } } ,
    Excellent = { Evade = 10, DelayOn = { 10, 30 } }
  },
  SEADGroupPrefixes = {},
  SuppressedGroups = {},
  EngagementRange = 75, --  default 75% engagement range Feature Request #1355
  Padding = 10,
  CallBack = nil,
  UseCallBack = false,
}

  --- Missile enumerators
  -- @field Harms
  SEAD.Harms = {
  ["AGM_88"] = "AGM_88",
  ["AGM_45"] = "AGM_45",
  ["AGM_122"] = "AGM_122",
  ["AGM_84"] = "AGM_84",
  ["AGM_45"] = "AGM_45",
  ["ALARM"] = "ALARM",
  ["LD-10"] = "LD-10",
  ["X_58"] = "X_58",
  ["X_28"] = "X_28",
  ["X_25"] = "X_25",
  ["X_31"] = "X_31",
  ["Kh25"] = "Kh25",
  }

  --- Missile enumerators - from DCS ME and Wikipedia
  -- @field HarmData
  SEAD.HarmData = {
  -- km and mach
  ["AGM_88"] = { 150, 3},
  ["AGM_45"] = { 12, 2},
  ["AGM_122"] = { 16.5, 2.3},
  ["AGM_84"] = { 280, 0.85},
  ["ALARM"] = { 45, 2},
  ["LD-10"] = { 60, 4},
  ["X_58"] = { 70, 4},
  ["X_28"] = { 80, 2.5},
  ["X_25"] = { 25, 0.76},
  ["X_31"] = {150, 3},
  ["Kh25"] = {25, 0.8},
  }

--- Creates the main object which is handling defensive actions for SA sites or moving SA vehicles.
-- When an anti radiation missile is fired (KH-58, KH-31P, KH-31A, KH-25MPU, HARM missiles), the SA will shut down their radars and will take evasive actions...
-- Chances are big that the missile will miss.
-- @param #SEAD self
-- @param #table SEADGroupPrefixes Table of #string entries or single #string, which is a table of Prefixes of the SA Groups in the DCS mission editor on which evasive actions need to be taken.
-- @param #number Padding (Optional) Extra number of seconds to add to radar switch-back-on time
-- @return #SEAD self
-- @usage
-- -- CCCP SEAD Defenses
-- -- Defends the Russian SA installations from SEAD attacks.
-- SEAD_RU_SAM_Defenses = SEAD:New( { 'RU SA-6 Kub', 'RU SA-6 Defenses', 'RU MI-26 Troops', 'RU Attack Gori' } )
function SEAD:New( SEADGroupPrefixes, Padding )

  local self = BASE:Inherit( self, BASE:New() )
  self:F( SEADGroupPrefixes )

  if type( SEADGroupPrefixes ) == 'table' then
    for SEADGroupPrefixID, SEADGroupPrefix in pairs( SEADGroupPrefixes ) do
      self.SEADGroupPrefixes[SEADGroupPrefix] = SEADGroupPrefix
    end
  else
    self.SEADGroupPrefixes[SEADGroupPrefixes] = SEADGroupPrefixes
  end

  local padding = Padding or 10
  if padding < 10 then padding = 10 end
  self.Padding = padding
  self.UseEmissionsOnOff = false
  
  self.CallBack = nil
  self.UseCallBack = false
  
  self:HandleEvent( EVENTS.Shot, self.HandleEventShot )

  self:I("*** SEAD - Started Version 0.3.2")
  return self
end

--- Update the active SEAD Set
-- @param #SEAD self
-- @param #table SEADGroupPrefixes The prefixes to add, note: can also be a single #string
-- @return #SEAD self
function SEAD:UpdateSet( SEADGroupPrefixes )

  self:T( SEADGroupPrefixes )

  if type( SEADGroupPrefixes ) == 'table' then
    for SEADGroupPrefixID, SEADGroupPrefix in pairs( SEADGroupPrefixes ) do
      self.SEADGroupPrefixes[SEADGroupPrefix] = SEADGroupPrefix
    end
  else
    self.SEADGroupPrefixes[SEADGroupPrefixes] = SEADGroupPrefixes
  end

  return self
end

--- Sets the engagement range of the SAMs. Defaults to 75% to make it more deadly. Feature Request #1355
-- @param #SEAD self
-- @param #number range Set the engagement range in percent, e.g. 50
-- @return #SEAD self
function SEAD:SetEngagementRange(range)
  self:T( { range } )
  range = range or 75
  if range < 0 or range > 100 then
    range = 75
  end
  self.EngagementRange = range
  self:T(string.format("*** SEAD - Engagement range set to %s",range))
  return self
end

--- Set the padding in seconds, which extends the radar off time calculated by SEAD
-- @param #SEAD self
-- @param #number Padding Extra number of seconds to add for the switch-on
-- @return #SEAD self
function SEAD:SetPadding(Padding)
  self:T( { Padding } )
  local padding = Padding or 10
  if padding < 10 then padding = 10 end
  self.Padding = padding
  return self
end

--- Set SEAD to use emissions on/off in addition to alarm state.
-- @param #SEAD self
-- @param #boolean Switch True for on, false for off.
-- @return #SEAD self
function SEAD:SwitchEmissions(Switch)
  self:T({Switch})
  self.UseEmissionsOnOff = Switch
  return self
end

--- Add an object to call back when going evasive.
-- @param #SEAD self
-- @param #table Object The object to call. Needs to have object functions as follows:
-- `:SeadSuppressionPlanned(Group, Name, SuppressionStartTime, SuppressionEndTime)` 
-- `:SeadSuppressionStart(Group, Name)`, 
-- `:SeadSuppressionEnd(Group, Name)`, 
-- @return #SEAD self
function SEAD:AddCallBack(Object)
  self:T({Class=Object.ClassName})
  self.CallBack = Object
  self.UseCallBack = true
  return self
end

--- Check if a known HARM was fired
-- @param #SEAD self
-- @param #string WeaponName
-- @return #boolean Returns true for a match
-- @return #string name Name of hit in table
function SEAD:_CheckHarms(WeaponName)
  self:T( { WeaponName } )
  local hit = false
  local name = ""
    for _,_name in pairs (SEAD.Harms) do
      if string.find(WeaponName,_name,1) then
        hit = true
        name = _name
        break
      end
    end
  return hit, name
end

--- (Internal) Return distance in meters between two coordinates or -1 on error.
-- @param #SEAD self
-- @param Core.Point#COORDINATE _point1 Coordinate one
-- @param Core.Point#COORDINATE _point2 Coordinate two
-- @return #number Distance in meters
function SEAD:_GetDistance(_point1, _point2)
  self:T("_GetDistance")
  if _point1 and _point2 then
    local distance1 = _point1:Get2DDistance(_point2)
    local distance2 = _point1:DistanceFromPointVec2(_point2)
    --self:T({dist1=distance1, dist2=distance2})
    if distance1 and type(distance1) == "number" then
      return distance1
    elseif distance2 and type(distance2) == "number" then
      return distance2
    else
      self:E("*****Cannot calculate distance!")
      self:E({_point1,_point2})
      return -1
    end
  else
    self:E("******Cannot calculate distance!")
    self:E({_point1,_point2})
    return -1
  end
end

--- Detects if an SAM site was shot with an anti radiation missile. In this case, take evasive actions based on the skill level set within the ME.
-- @see SEAD
-- @param #SEAD
-- @param Core.Event#EVENTDATA EventData
-- @return #SEAD self
function SEAD:HandleEventShot( EventData )
  self:T( { EventData.id } )
  local SEADPlane = EventData.IniUnit -- Wrapper.Unit#UNIT
  local SEADPlanePos = SEADPlane:GetCoordinate() -- Core.Point#COORDINATE
  local SEADUnit = EventData.IniDCSUnit
  local SEADUnitName = EventData.IniDCSUnitName
  local SEADWeapon = EventData.Weapon -- Identify the weapon fired
  local SEADWeaponName = EventData.WeaponName -- return weapon type

  self:T( "*** SEAD - Missile Launched = " .. SEADWeaponName)
  --self:T({ SEADWeapon })

  if self:_CheckHarms(SEADWeaponName) then
    self:T( '*** SEAD - Weapon Match' )
    local _targetskill = "Random"
    local _targetgroupname = "none"
    local _target = EventData.Weapon:getTarget() -- Identify target
    local _targetUnit = UNIT:Find(_target) -- Wrapper.Unit#UNIT
    local _targetgroup = nil -- Wrapper.Group#GROUP
    if _targetUnit and _targetUnit:IsAlive() then
      _targetgroup = _targetUnit:GetGroup()
      _targetgroupname = _targetgroup:GetName() -- group name
      local _targetUnitName = _targetUnit:GetName()
      _targetUnit:GetSkill()
      _targetskill = _targetUnit:GetSkill()
    end
    -- see if we are shot at
    local SEADGroupFound = false
    for SEADGroupPrefixID, SEADGroupPrefix in pairs( self.SEADGroupPrefixes ) do
      self:T( _targetgroupname, SEADGroupPrefix )
      if string.find( _targetgroupname, SEADGroupPrefix ) then
        SEADGroupFound = true
        self:T( '*** SEAD - Group Match Found' )
        break
      end
    end
    if SEADGroupFound == true then -- yes we are being attacked
      if _targetskill == "Random" then -- when skill is random, choose a skill
        local Skills = { "Average", "Good", "High", "Excellent" }
        _targetskill = Skills[ math.random(1,4) ]
      end
      --self:T( _targetskill )
      if self.TargetSkill[_targetskill] then
        local _evade = math.random (1,100) -- random number for chance of evading action
        if (_evade > self.TargetSkill[_targetskill].Evade) then
          self:T("*** SEAD - Evading")
          -- calculate distance of attacker
          local _targetpos = _targetgroup:GetCoordinate()
          local _distance = self:_GetDistance(SEADPlanePos, _targetpos)
          -- weapon speed
          local hit, data = self:_CheckHarms(SEADWeaponName)
          local wpnspeed = 666 -- ;)
          local reach = 10
          if hit then
            local wpndata = SEAD.HarmData[data]
            reach = wpndata[1] * 1,1
            local mach = wpndata[2]
            wpnspeed = math.floor(mach * 340.29)
          end
          -- time to impact
          local _tti = math.floor(_distance / wpnspeed) -- estimated impact time
          if _distance > 0 then
            _distance = math.floor(_distance / 1000) -- km
          else
            _distance = 0
          end

          self:T( string.format("*** SEAD - target skill %s, distance %dkm, reach %dkm, tti %dsec", _targetskill, _distance,reach,_tti ))

          if reach >= _distance then
            self:T("*** SEAD - Shot in Reach")

            local function SuppressionStart(args)
              self:T(string.format("*** SEAD - %s Radar Off & Relocating",args[2]))
              local grp = args[1] -- Wrapper.Group#GROUP
              local name = args[2] -- #string Group Name 
              if self.UseEmissionsOnOff then
                grp:EnableEmission(false)
              else
               grp:OptionAlarmStateGreen()
              end
              grp:RelocateGroundRandomInRadius(20,300,false,false,"Diamond")
              if self.UseCallBack then
                local object = self.CallBack
                object:SeadSuppressionStart(grp,name)
              end
            end

            local function SuppressionStop(args)
              self:T(string.format("*** SEAD - %s Radar On",args[2]))
              local grp = args[1]  -- Wrapper.Group#GROUP
              local name = args[2] -- #string Group Nam
              if self.UseEmissionsOnOff then
                grp:EnableEmission(true)
              else
                grp:OptionAlarmStateRed()
              end
              grp:OptionEngageRange(self.EngagementRange)
              self.SuppressedGroups[name] = false
              if self.UseCallBack then
                local object = self.CallBack
                object:SeadSuppressionEnd(grp,name)
              end
            end

            -- randomize switch-on time
            local delay = math.random(self.TargetSkill[_targetskill].DelayOn[1], self.TargetSkill[_targetskill].DelayOn[2])
            if delay > _tti then delay = delay / 2 end -- speed up
            if _tti > (3*delay) then delay = (_tti / 2) * 0.9 end -- shot from afar

            local SuppressionStartTime = timer.getTime() + delay
            local SuppressionEndTime = timer.getTime() + _tti + self.Padding

            if not self.SuppressedGroups[_targetgroupname] then
              self:T(string.format("*** SEAD - %s | Parameters TTI %ds | Switch-Off in %ds",_targetgroupname,_tti,delay))
              timer.scheduleFunction(SuppressionStart,{_targetgroup,_targetgroupname},SuppressionStartTime)
              timer.scheduleFunction(SuppressionStop,{_targetgroup,_targetgroupname},SuppressionEndTime)
              self.SuppressedGroups[_targetgroupname] = true
              if self.UseCallBack then
                local object = self.CallBack
                object:SeadSuppressionPlanned(_targetgroup,_targetgroupname,SuppressionStartTime,SuppressionEndTime)
              end
            end

          end
        end
      end
    end
  end
  return self
end