local transforms = asset.require('scene/solarsystem/planets/earth/transforms')
local assetHelper = asset.require('util/asset_helper')

function downloadTLEFile(sceneAsset, url, name, filename)
    local identifier = name
    identifier = identifier:gsub(" ", "")
    identifier = identifier:gsub("&", "")
    identifier = identifier:gsub("-", "")

    local urlSyncTable = {
        Name = "Satellite TLE Data (" .. name .. ")",
        Type = "UrlSynchronization",
        Identifier = "satellite_tle_data_" .. identifier,
        Url = url,
        Override = true
    }

    if (filename ~= '')  then
        urlSyncTable.Filename = filename
    end

    return sceneAsset.syncedResource(urlSyncTable)
end

-- Check format of a set of 3 TLE file lines and return nonzero if there is a format error
function isValidTLEFileFormat(lineArr)
    function isEmpty(s) return s == nil or s == '' end

    if isEmpty(lineArr[1]) or isEmpty(lineArr[2]) or isEmpty(lineArr[3]) then
        return false
    end
    if string.sub(lineArr[2], 1, 2) ~= "1 " then
        return false
    end
    if string.sub(lineArr[3], 1, 2) ~= "2 " then
        return false
    end
    return true
end

local makeSingleLineElement = function(tle, filename)
  local path = tle .. "/" .. filename
  local file = io.open(path, "r")
  assert(file, "File not found: " .. path)

    local line = {
    file:read('*l'), --title line
    file:read('*l'),
    file:read('*l')
  }

  assert(isValidTLEFileFormat(line), "TLE file syntax error on line " .. 1 .. ": " .. path)

  -- Trim string
  line[1] = line[1]:gsub("^%s*(.-)%s*$", "%1")
  line[1] = line[1]:gsub("%s+", "_")
  line[1] = line[1]:gsub("[%-()]", "")
  --local title = line[1]

  return line
end

function numLinesInFile(filename)
    local ctr = 0
    for _ in io.lines(filename) do ctr = ctr + 1 end
    return ctr
end

local getPeriodFromElement = function(element)
  -- Get period from correct location of the string
  local per = tonumber(string.sub(element[3], 53, 63))
  -- Trail for 2x a single revolution
  per = 1.0 / per

  return per
end

function satellites(title, file, color, group)
    return {
       Identifier = title,
       Parent = transforms.EarthInertial.Identifier,
       Renderable = {
            Type = "RenderableSatellites",
            Path = file,
            SegmentQuality = 3,
            Color = color,
            Fade = 1.5
        },
        Tag = { "earth_satellites" },
        GUI = {
            Path = "/Solar System/Planets/Earth/Satellites"
       }
    }
end

local registerSatelliteGroupObjects = function(containingAsset, group, tleFolder, shouldAddDuplicates)
    local filename = group.Url:match("([^/]+)$")
    local filenameSansExt = filename:gsub(filename:match("(%.%w+)$"), "")

    local path = tleFolder .. "/" .. filename

    local SatelliteBatch = satellites(filenameSansExt, path, group.TrailColor, group)
    assetHelper.registerSceneGraphNodesAndExport(containingAsset, { SatelliteBatch })
end

asset.export("downloadTLEFile", downloadTLEFile)
asset.export("isValidTLEFileFormat", isValidTLEFileFormat)
asset.export("numLinesInFile", numLinesInFile)
asset.export("makeSingleLineElement", makeSingleLineElement)
asset.export("getPeriodFromElement", getPeriodFromElement)
asset.export("registerSatelliteGroupObjects", registerSatelliteGroupObjects)