CpFieldUtil = {}
-- force reload
CpFieldUtil.groundTypeModifier = nil

function CpFieldUtil.isNodeOnField(node, fieldId)
    local x, y, z = getWorldTranslation(node)
    local isOnField, _ = FSDensityMapUtil.getFieldDataAtWorldPosition(x, y, z)
    if isOnField and fieldId then
        return fieldId == CpFieldUtil.getFieldIdAtWorldPosition(x, z)
    end
    return isOnField
end

function CpFieldUtil.isNodeOnFieldArea(node)
    local x, _, z = getWorldTranslation(node)
    return CpFieldUtil.isOnFieldArea(x, z)
end

--- Is the relative position dx/dz on the same field as node?
function CpFieldUtil.isOnSameField(node, dx, dy)

end

function CpFieldUtil.isOnField(x, z, fieldId)
    local y = getTerrainHeightAtWorldPos(g_currentMission.terrainRootNode, x, 1, z);
    local isOnField, _ = FSDensityMapUtil.getFieldDataAtWorldPosition(x, y, z)
    if isOnField and fieldId then
        return fieldId == CpFieldUtil.getFieldIdAtWorldPosition(x, z)
    end
    return isOnField
end

function CpFieldUtil.initFieldMod()
    local groundTypeMapId, groundTypeFirstChannel, groundTypeNumChannels =
        g_currentMission.fieldGroundSystem:getDensityMapData(FieldDensityMap.GROUND_TYPE)
    CpFieldUtil.groundTypeModifier = DensityMapModifier.new(groundTypeMapId, groundTypeFirstChannel, groundTypeNumChannels,
            g_currentMission.terrainRootNode)
    CpFieldUtil.groundTypeFilter = DensityMapFilter.new(CpFieldUtil.groundTypeModifier)
end

function CpFieldUtil.isOnFieldArea(x, z)
    if CpFieldUtil.groundTypeModifier == nil then
        CpFieldUtil.initFieldMod()
    end
    local w, h = 1, 1
    CpFieldUtil.groundTypeModifier:setParallelogramWorldCoords(x - w / 2, z - h / 2, w, 0, 0, h, DensityCoordType.POINT_VECTOR_VECTOR)
    CpFieldUtil.groundTypeFilter:setValueCompareParams(DensityValueCompareType.GREATER, 0)
    local density, area, totalArea = CpFieldUtil.groundTypeModifier:executeGet(CpFieldUtil.groundTypeFilter)
    return area > 0, area, totalArea
end

--- Which field this node is on.
---@param node table Giants engine node
---@return number 0 if not on any field, otherwise the number of field, see note on getFieldIdAtWorldPosition()
function CpFieldUtil.getFieldNumUnderNode(node)
    local x, _, z = getWorldTranslation(node)
    return CpFieldUtil.getFieldIdAtWorldPosition(x, z)
end

--- Which field this node is on. See above for more info
function CpFieldUtil.getFieldNumUnderVehicle(vehicle)
    return CpFieldUtil.getFieldNumUnderNode(vehicle.rootNode)
end

--- Returns a field ID for a position. This really is the ID of the first field which is
--- on the same farmland where the given position is. The farmland is what you can buy in the game,
--- including the area around an actual field, and may extend well beyond the actual field.
--- So do not use this the determine the field ID of a given position, as this does not guarantee
--- that the position is actually on a field.
function CpFieldUtil.getFieldIdAtWorldPosition(posX, posZ)
    local farmland = g_farmlandManager:getFarmlandAtWorldPosition(posX, posZ)
    if farmland ~= nil then
        local fieldMapping = g_fieldManager.farmlandIdFieldMapping[farmland.id]
        if fieldMapping ~= nil and fieldMapping[1] ~= nil then
            return fieldMapping[1].fieldId
        end
    end
    return 0
end


function CpFieldUtil.saveAllFields()
    local fileName = string.format('%s/cpFields.xml', g_Courseplay.debugPrintDir)
    local xmlFile = createXMLFile("cpFields", fileName, "CPFields");
    if xmlFile and xmlFile ~= 0 then
        for _, field in pairs(g_fieldManager:getFields()) do
            local valid, points = g_fieldScanner:findContour(field.posX, field.posZ)
            if valid then
                local key = ("CPFields.field(%d)"):format(field.fieldId);
                setXMLInt(xmlFile, key .. '#fieldNum',	field.fieldId);
                setXMLInt(xmlFile, key .. '#numPoints', #points);
                for i, point in ipairs(points) do
                    setXMLString(xmlFile, key .. (".point%d#pos"):format(i), ("%.2f %.2f %.2f"):format(point.x, point.y, point.z))
                end
                local islandNodes = Island.findIslands( Polygon:new(CourseGenerator.pointsToXy(points)))
                CourseGenerator.pointsToXzInPlace(islandNodes)
                for i, islandNode in ipairs(islandNodes) do
                    setXMLString(xmlFile, key .. ( ".islandNode%d#pos"):format( i ), ("%.2f %2.f"):format( islandNode.x, islandNode.z ))
                end
                CpUtil.info('Field %d saved', field.fieldId)
            else
                CpUtil.info('Field %d could not be saved', field.fieldId)
            end
        end
        saveXMLFile(xmlFile);
        delete(xmlFile);
        
        CpUtil.info('Saved all fields to %s', fileName)
    else
        CpUtil.info("Error: field could not be saved to " , g_Courseplay.debugPrintDir);
    end;
end

function CpFieldUtil.initializeFieldMod()
    CpFieldUtil.fieldMod = {}
    CpFieldUtil.fieldMod.modifier = DensityMapModifier:new(g_currentMission.terrainDetailId, g_currentMission.terrainDetailTypeFirstChannel, g_currentMission.terrainDetailTypeNumChannels)
    CpFieldUtil.fieldMod.filter = DensityMapFilter:new(CpFieldUtil.fieldMod.modifier)
end

function CpFieldUtil.isField(x, z, widthX, widthZ)
    if not CpFieldUtil.fieldMod then
        CpFieldUtil.initializeFieldMod()
    end
    widthX = widthX or 0.5
    widthZ = widthZ or 0.5
    local startWorldX, startWorldZ   = x, z
    local widthWorldX, widthWorldZ   = x - widthX, z - widthZ
    local heightWorldX, heightWorldZ = x + widthX, z + widthZ

    CpFieldUtil.fieldMod.modifier:setParallelogramWorldCoords(startWorldX, startWorldZ, widthWorldX, widthWorldZ, heightWorldX, heightWorldZ, "ppp")
    CpFieldUtil.fieldMod.filter:setValueCompareParams("greater", 0)

    local _, area, totalArea = CpFieldUtil.fieldMod.modifier:executeGet(CpFieldUtil.fieldMod.filter)
    local isField = area > 0
    return isField, area, totalArea
end

--- Get the field polygon (field edge vertices) at the world position.
--- If there is also a custom field at the position it may return that, depending on the user's preference set.
---@return Polygon, boolean the field polygon, nil if not on field. True if a custom field was selected
function CpFieldUtil.getFieldPolygonAtWorldPosition(x, z)
    local fieldPolygon, isCustomField
    local customField = g_customFieldManager:getCustomField(x, z)
    local fieldNum = CpFieldUtil.getFieldIdAtWorldPosition(x, z)
    CpUtil.info('Scanning field %d on %s, prefer custom fields %s',
            fieldNum, g_currentMission.missionInfo.mapTitle, g_Courseplay.globalSettings.preferCustomFields:getValue())
    local mapField, mapFieldPolygon = g_fieldScanner:findContour(x, z)

    if customField and (not mapField or g_Courseplay.globalSettings.preferCustomFields:getValue()) then
        -- use a custom field if there is one under us and either there's no regular map field or, there is,
        -- but the user prefers custom fields
        CpUtil.info('Custom field found: %s', customField:getName())
        fieldPolygon = customField:getVertices()
        isCustomField = true
    elseif mapField then
        fieldPolygon = mapFieldPolygon
    end
    return fieldPolygon, isCustomField
end