-- Load external library (should be in the same folder as main.lua)
local ui = require("ui")
 
-- Labels for digital display
local headingGeo = ui.newLabel{
        bounds = { 25, 47, 88, 46 },
        text = "0°",
        font = "Helvetica-Bold",
        textColor = { 35, 170, 255, 255 },
        size = 38,
        align = "right"
}
 
local directionGeo = ui.newLabel{
        bounds = { 111, 66, 31, 24 },
        text = "N",
        font = "Helvetica-Bold",
        textColor = { 35, 170, 255, 255 },
        size = 16,
        align = "left"
}
 
local headingMag = ui.newLabel{
        bounds = { 175, 47, 88, 46 },
        text = "0°",
        font = "Helvetica-Bold",
        textColor = { 153, 153, 153, 255 },
        size = 38,
        align = "right"
}
 
local directionMag = ui.newLabel{
        bounds = { 261, 66, 31, 24 },
        text = "N",
        font = "Helvetica-Bold",
        textColor = { 153, 153, 153, 255 },
        size = 16,
        align = "left"
}
 
local dial = display.newImage("compass_dial.png", 40, 150)
local background = display.newImage("compass_bkg.png")
 
local compassMode = "geo"
 
local showGeo = function( event )
print("geo")
        headingGeo:setTextColor( 35, 170, 255, 255 )
        directionGeo:setTextColor( 35, 170, 255, 255 )
        headingMag:setTextColor( 153, 153, 153, 255 )
        directionMag:setTextColor( 153, 153, 153, 255 )
        compassMode = "geo"
end
 
local showMag = function( event )
print("mag")
        headingGeo:setTextColor( 153, 153, 153, 255 )
        directionGeo:setTextColor( 153, 153, 153, 255 )
        headingMag:setTextColor( 35, 170, 255, 255 )
        directionMag:setTextColor( 35, 170, 255, 255 )
        compassMode = "mag"
end
 
-- Add touch events to textfields (for switching between geographic/magnetic display modes)
headingGeo:addEventListener( "touch", showGeo )
headingMag:addEventListener( "touch", showMag )
 
local directionForAngle = function( angle )
        local text
 
        if ( angle <= 22 or angle > 337 ) then
                text = "N"
        elseif ( angle > 22 and angle <= 67 ) then
                text = "NE"
        elseif ( angle > 67 and angle <= 112 ) then
                text = "E"
        elseif ( angle > 112 and angle <= 157 ) then
                text = "SE"
        elseif ( angle > 157 and angle <= 202 ) then
                text = "S"
        elseif ( angle > 202 and angle <= 247 ) then
                text = "SW"
        elseif ( angle > 247 and angle <= 292 ) then
                text = "W"
        elseif ( angle > 292 and angle <= 337 ) then
                text = "NW"
        end
        
        return text
end
 
local dstRotation = 0
 
local updateCompass = function( event )
 
        local angleMag, angleGeo
        
        -- Note: "magnetic" = magnetic north heading, and "geographic" = "true north" heading as seen on a map
        -- (The variance between these heading values depends on your position on the Earth)
 
        angleMag = event.magnetic
 
        -- Android does not support geographic headings, so we use magnetic headings for Android builds
        if system.getInfo( "platformName" ) ~= "Android" then
                angleGeo = event.geographic
        else
                angleGeo = angleMag
        end
        
        if ( "geo" == compassMode ) then
                dstRotation = -angleGeo
        else
                dstRotation = -angleMag
        end
        
        -- Format strings as whole numbers
        local valueGeo = string.format( '%.0f', angleGeo )
        local valueMag = string.format( '%.0f', angleMag )
 
        headingGeo:setText( valueGeo .. "°" )
        directionGeo:setText( directionForAngle( angleGeo ) )
        
        headingMag:setText( valueMag .. "°" )
        directionMag:setText( directionForAngle( angleMag ) )
end
 
local animateDial = function( event )
        local curRotation = dial.rotation
        local delta = dstRotation - curRotation
        
        if math.abs( delta ) >= 180 then
                if delta < -180 then
                        delta = delta + 360
                elseif delta > 180 then
                        delta = delta - 360
                end
        end
 
        dial.rotation = curRotation + delta*0.3
end
 
local didInitGPS = false
local initGPS = function( event )
        if ( not didInitGPS ) then
                didInitGPS = true
 
                -- We only need a single location event to calibrate "true north", then we can turn off GPS again
                local initDone = function( event )
                        Runtime:removeEventListener( "location", initGPS )
                end
 
                -- Delay removal to let the hardware activate
                timer.performWithDelay( 1000, initDone )
        end
end
 
-- Determine if running on Corona Simulator
--
local isSimulator = "simulator" == system.getInfo("environment")
 
-- Heading Events are not supported on Simulator
--
if isSimulator then
        msg = display.newText( "Heading events not supported on Simulator!", 0, 20, "Verdana-Bold", 12 )
        msg.x = display.contentWidth/2          -- center title
        msg:setTextColor( 255,255,0 )
end
 
-- Location event listener
if system.getInfo( "platformName" ) ~= "Android" then
        Runtime:addEventListener( "location", initGPS )
end
-- This is not required if you only want the heading relative to magnetic north, but to calculate 
-- your "true north" offset, the iPhone needs at least one location reading. Location may already 
-- be cached by the OS, but if not, then geographic north heading defaults to "-1".
-- Again, this is not required for Android, since Android does not support true north headings.
 
-- Compass event listener
Runtime:addEventListener( "heading", updateCompass )
 
-- Adaptive tweening to smooth the dial animation
Runtime:addEventListener( "enterFrame", animateDial )