package main

import (
  "fmt"
  "machine"
  "net/netip"
  "time"
  "image/color"

  "tinygo.org/x/drivers/ssd1306"
  "tinygo.org/x/tinyfont"
  "tinygo.org/x/tinyfont/freesans"
  "tinygo.org/x/tinyfont/proggy"
)

var (
  defaultFont = &freesans.Regular9pt7b
  tinyFont = &proggy.TinySZ8pt7b
)

// -------------------------------------------------------------
// Panic Handler & Entry Point
// -------------------------------------------------------------
func panicErr(msg string, err error) {
  if err != nil {
    println("FATAL:", msg, "-", err.Error())
  }
  for {
    time.Sleep(500 * time.Millisecond)
  }
}

// syncNTP triggers an NTP request and polls until completed or timed out.
func syncNTP(stack *NetworkStack, server netip.Addr, timeout time.Duration) (time.Duration, error) {
  if err := stack.stack.StartNTP(server); err != nil {
    return 0, fmt.Errorf("start NTP: %w", err)
  }

  deadline := time.Now().Add(timeout)
  for time.Now().Before(deadline) {
    offset, done := stack.stack.ResultNTPOffset()
    if done {
      return offset, nil
    }
    time.Sleep(50 * time.Millisecond)
  }

  return 0, fmt.Errorf("NTP request timed out")
}

func main() {
  time.Sleep(2 * time.Second)
  println("Starting app...")

  // Bump frequency to 400kHz for snappy display flushes
  i2c := machine.I2C0
  err := i2c.Configure(machine.I2CConfig{
    Frequency: 400 * machine.KHz,
    SDA:       machine.GPIO4,
    SCL:       machine.GPIO5,
  })
  if err != nil {
    panicErr("I2C configuration", err)
  }

  // Instantiate nil oled variable
  var oled *ssd1306.Device
  // White color for display
  white := color.RGBA{R: 255, G: 255, B: 255, A: 255}

  // Probe address 0x3C with a zero-byte or 1-byte read
  println("Initializing display...")
  var dummy [1]byte
  if err := i2c.ReadRegister(0x3C, 0x00, dummy[:]); err == nil {
      println("SSD1306 detected at 0x3C")
      dev := ssd1306.NewI2C(i2c)
      dev.Configure(ssd1306.Config{
          Address: 0x3C,
          Width:   128,
          Height:  64,
      })
      oled = dev

      // Run some initial clearing and add booting text to the screen
      oled.ClearBuffer()
      tinyfont.WriteLine(oled, defaultFont, 0, 32, "Booting...", white)
      oled.Display()
      time.Sleep(1 * time.Second)
  } else {
      panicErr("Failed to init display.", err)
  }

  println("Starting Wi-Fi...")
  oled.ClearBuffer()
  tinyfont.WriteLine(oled, defaultFont, 0, 32, "Starting Wi-Fi...", white)
  oled.Display()

  netStack, err := InitNetwork(WifiSSID, WifiPass)
  if err != nil {
    panicErr("network init", err)
  }

  println("Wi-Fi Connected!")
  oled.ClearBuffer()
  tinyfont.WriteLine(oled, defaultFont, 0, 32, "Wi-Fi Connected!", white)
  oled.Display()
  time.Sleep(1 * time.Second)

  // Extract IP string from the returned NetworkStack
  ipStr := netStack.localIP.String()

  // Sync wall time using public NTP (e.g. Cloudflare: 162.159.200.1 / time.cloudflare.com)
  println("Synchronizing clock via NTP...")
  oled.ClearBuffer()
  tinyfont.WriteLine(oled, defaultFont, 0, 32, "Syncing NTP...", white)
  oled.Display()
  ntpServer := netip.MustParseAddr("162.159.200.1")
  timeOffset, err := syncNTP(netStack, ntpServer, 5*time.Second)
  if err != nil {
    panicErr("NTP sync failed", err)
  }

  println("NTP synced successfully!")
  oled.ClearBuffer()
  tinyfont.WriteLine(oled, defaultFont, 0, 32, "NTP synced!", white)
  oled.Display()
  time.Sleep(1 * time.Second)

  lastSecond := -1

  // Remove static call before the loop, then in the loop:
  for {
    currentTime := time.Now().Add(timeOffset).UTC()
    currentSecond := currentTime.Second()

    if currentSecond != lastSecond {
      lastSecond = currentSecond

      timeSeperator := ":"
      if currentSecond%2 == 1 {
        timeSeperator = " "
      }

      // Dynamically determine DST vs Standard time for this second
      loc, zoneName := ResolveTimezone(ActiveTimezone, currentTime)
      localTime := currentTime.In(loc)

      timeStr := fmt.Sprintf("%02d%s%02d%s%02d %s",
        localTime.Hour(), timeSeperator,
        localTime.Minute(), timeSeperator,
        localTime.Second(),
        zoneName)

      oled.ClearBuffer()
      tinyfont.WriteLine(oled, defaultFont, 8, 32, timeStr, white)
      tinyfont.WriteLine(oled, tinyFont, 0, 60, fmt.Sprintf("IP: %s", ipStr), white)
      oled.Display()
    }

    time.Sleep(10 * time.Millisecond)
  }
}