//go:build pluto && linux

package plutosdr

/*
#cgo pkg-config: libiio
#include <iio.h>
#include <stdlib.h>
#include <stdint.h>
*/
import "C"

import (
	"context"
	"fmt"
	"log"
	"sync"
	"sync/atomic"
	"time"
	"unsafe"

	"github.com/jan/fm-rds-tx/internal/output"
	"github.com/jan/fm-rds-tx/internal/platform"
)

type PlutoDriver struct {
	mu  sync.Mutex
	cfg platform.SoapyConfig

	ctx    *C.struct_iio_context
	txDev  *C.struct_iio_device
	phyDev *C.struct_iio_device
	chanI  *C.struct_iio_channel
	chanQ  *C.struct_iio_channel
	chanLO *C.struct_iio_channel
	buf    *C.struct_iio_buffer
	bufSize int

	started        bool
	configured     bool
	framesWritten  atomic.Uint64
	samplesWritten atomic.Uint64
	underruns      atomic.Uint64
	lastError      string
	lastErrorAt    string
	layoutLogged   bool
}

func NewPlutoDriver() platform.SoapyDriver {
	return &PlutoDriver{}
}

func (d *PlutoDriver) Name() string { return "pluto-iio" }

func (d *PlutoDriver) Configure(_ context.Context, cfg platform.SoapyConfig) error {
	d.mu.Lock()
	defer d.mu.Unlock()

	d.cleanup()
	d.cfg = cfg

	uri := "usb:"
	if cfg.Device != "" && cfg.Device != "plutosdr" {
		uri = cfg.Device
	}
	if v, ok := cfg.DeviceArgs["uri"]; ok && v != "" {
		uri = v
	}

	cURI := C.CString(uri)
	defer C.free(unsafe.Pointer(cURI))
	ctx := C.iio_create_context_from_uri(cURI)
	if ctx == nil {
		return fmt.Errorf("pluto: failed to create IIO context (uri=%s)", uri)
	}
	d.ctx = ctx

	txDev := d.findDevice("cf-ad9361-dds-core-lpc")
	if txDev == nil {
		return fmt.Errorf("pluto: TX device 'cf-ad9361-dds-core-lpc' not found")
	}
	d.txDev = txDev

	phyDev := d.findDevice("ad9361-phy")
	if phyDev == nil {
		return fmt.Errorf("pluto: PHY device 'ad9361-phy' not found")
	}
	d.phyDev = phyDev

	phyChanTX := d.findChannel(phyDev, "voltage3", true)
	if phyChanTX == nil {
		phyChanTX = d.findChannel(phyDev, "voltage0", true)
	}
	if phyChanTX == nil {
		return fmt.Errorf("pluto: PHY TX channel not found (tried voltage3, voltage0)")
	}

	rate := int64(cfg.SampleRateHz)
	if rate < 2084000 {
		rate = 2084000
	}
	d.cfg.SampleRateHz = float64(rate)
	if err := d.writeChanAttrLL(phyChanTX, "sampling_frequency", rate); err != nil {
		return err
	}

	bw := rate
	if bw > 2000000 {
		bw = 2000000
	}
	if err := d.writeChanAttrLL(phyChanTX, "rf_bandwidth", bw); err != nil {
		return err
	}

	phyChanLO := d.findChannel(phyDev, "altvoltage1", true)
	d.chanLO = phyChanLO
	if phyChanLO != nil {
		freqHz := int64(cfg.CenterFreqHz)
		if freqHz <= 0 {
			freqHz = 100000000
		}
		if err := d.writeChanAttrLL(phyChanLO, "frequency", freqHz); err != nil {
			return err
		}
	}

	attenDB := int64(0)
	if cfg.GainDB > 0 {
		attenDB = -int64(89 - cfg.GainDB)
		if attenDB > 0 {
			attenDB = 0
		}
		if attenDB < -89 {
			attenDB = -89
		}
	}
	_ = d.writeChanAttrLL(phyChanTX, "hardwaregain", attenDB*1000)

	chanI := d.findChannel(txDev, "voltage0", true)
	chanQ := d.findChannel(txDev, "voltage1", true)
	if chanI == nil || chanQ == nil {
		return fmt.Errorf("pluto: TX I/Q channels not found on streaming device")
	}
	C.iio_channel_enable(chanI)
	C.iio_channel_enable(chanQ)
	d.chanI = chanI
	d.chanQ = chanQ

	d.bufSize = int(rate) / 20
	if d.bufSize < 4096 {
		d.bufSize = 4096
	}
	buf := C.iio_device_create_buffer(txDev, C.size_t(d.bufSize), C.bool(false))
	if buf == nil {
		return fmt.Errorf("pluto: failed to create TX buffer (size=%d)", d.bufSize)
	}
	d.buf = buf
	d.configured = true
	return nil
}

func (d *PlutoDriver) Capabilities(_ context.Context) (platform.DeviceCaps, error) {
	return platform.DeviceCaps{
		MinSampleRate: 521e3,
		MaxSampleRate: 61.44e6,
		HasGain:       true,
		GainMinDB:     -89,
		GainMaxDB:     0,
		Channels:      []int{0},
	}, nil
}

func (d *PlutoDriver) Start(_ context.Context) error {
	d.mu.Lock()
	defer d.mu.Unlock()
	if !d.configured {
		return fmt.Errorf("pluto: not configured")
	}
	if d.started {
		return fmt.Errorf("pluto: already started")
	}
	d.started = true
	return nil
}

func (d *PlutoDriver) Write(_ context.Context, frame *output.CompositeFrame) (int, error) {
	d.mu.Lock()
	buf := d.buf
	chanI := d.chanI
	chanQ := d.chanQ
	started := d.started
	bufSize := d.bufSize
	d.mu.Unlock()

	if !started || buf == nil {
		return 0, fmt.Errorf("pluto: not active")
	}
	if frame == nil || len(frame.Samples) == 0 {
		return 0, nil
	}

	written := 0
	total := len(frame.Samples)

	for written < total {
		chunk := total - written
		if chunk > bufSize {
			chunk = bufSize
		}

		step := uintptr(C.iio_buffer_step(buf))
		if step == 0 {
			return written, fmt.Errorf("pluto: buffer step is 0")
		}

		ptrI := uintptr(C.iio_buffer_first(buf, chanI))
		ptrQ := uintptr(C.iio_buffer_first(buf, chanQ))
		if ptrI == 0 || ptrQ == 0 {
			return written, fmt.Errorf("pluto: buffer_first returned null")
		}

		end := uintptr(C.iio_buffer_end(buf))
		d.mu.Lock()
		if !d.layoutLogged {
			delta := int64(ptrQ) - int64(ptrI)
			span := int64(0)
			if end > ptrI {
				span = int64(end - ptrI)
			}
			log.Printf("pluto-linux: buffer layout step=%d ptrI=%#x ptrQ=%#x delta=%d end=%#x span=%d bufSize=%d", step, ptrI, ptrQ, delta, end, span, bufSize)
			d.layoutLogged = true
		}
		d.mu.Unlock()
		if end > 0 {
			bufSamples := int((end - ptrI) / step)
			if bufSamples > 0 && chunk > bufSamples {
				chunk = bufSamples
			}
		}

		for i := 0; i < chunk; i++ {
			s := frame.Samples[written+i]
			*(*int16)(unsafe.Pointer(ptrI)) = int16(s.I * 32767)
			*(*int16)(unsafe.Pointer(ptrQ)) = int16(s.Q * 32767)
			ptrI += step
			ptrQ += step
		}

		pushed := int(C.iio_buffer_push(buf))
		if pushed < 0 {
			d.mu.Lock()
			d.lastError = fmt.Sprintf("buffer_push: %d", pushed)
			d.lastErrorAt = time.Now().UTC().Format(time.RFC3339)
			d.underruns.Add(1)
			d.mu.Unlock()
			return written, fmt.Errorf("pluto: buffer_push returned %d", pushed)
		}

		written += chunk
	}

	d.framesWritten.Add(1)
	d.samplesWritten.Add(uint64(written))
	return written, nil
}

func (d *PlutoDriver) Stop(_ context.Context) error {
	d.mu.Lock()
	defer d.mu.Unlock()
	d.started = false
	return nil
}

func (d *PlutoDriver) Flush(_ context.Context) error { return nil }

func (d *PlutoDriver) Tune(_ context.Context, freqHz float64) error {
	d.mu.Lock()
	defer d.mu.Unlock()
	if !d.configured || d.chanLO == nil {
		return fmt.Errorf("pluto: not configured or LO channel not available")
	}
	return d.writeChanAttrLL(d.chanLO, "frequency", int64(freqHz))
}

func (d *PlutoDriver) Close(_ context.Context) error {
	d.mu.Lock()
	defer d.mu.Unlock()
	d.started = false
	d.cleanup()
	return nil
}

func (d *PlutoDriver) Stats() platform.RuntimeStats {
	d.mu.Lock()
	defer d.mu.Unlock()
	return platform.RuntimeStats{
		TXEnabled:      d.started,
		StreamActive:   d.started && d.buf != nil,
		FramesWritten:  d.framesWritten.Load(),
		SamplesWritten: d.samplesWritten.Load(),
		Underruns:      d.underruns.Load(),
		LastError:      d.lastError,
		LastErrorAt:    d.lastErrorAt,
		EffectiveRate:  d.cfg.SampleRateHz,
	}
}

func (d *PlutoDriver) cleanup() {
	if d.buf != nil {
		C.iio_buffer_destroy(d.buf)
		d.buf = nil
	}
	if d.chanI != nil {
		C.iio_channel_disable(d.chanI)
		d.chanI = nil
	}
	if d.chanQ != nil {
		C.iio_channel_disable(d.chanQ)
		d.chanQ = nil
	}
	d.chanLO = nil
	if d.ctx != nil {
		C.iio_context_destroy(d.ctx)
		d.ctx = nil
	}
	d.txDev = nil
	d.phyDev = nil
	d.configured = false
	d.layoutLogged = false
}

func (d *PlutoDriver) findDevice(name string) *C.struct_iio_device {
	if d.ctx == nil {
		return nil
	}
	cName := C.CString(name)
	defer C.free(unsafe.Pointer(cName))
	return C.iio_context_find_device(d.ctx, cName)
}

func (d *PlutoDriver) findChannel(dev *C.struct_iio_device, name string, isOutput bool) *C.struct_iio_channel {
	if dev == nil {
		return nil
	}
	cName := C.CString(name)
	defer C.free(unsafe.Pointer(cName))
	if isOutput {
		return C.iio_device_find_channel(dev, cName, C.bool(true))
	}
	return C.iio_device_find_channel(dev, cName, C.bool(false))
}

func (d *PlutoDriver) writeChanAttrLL(ch *C.struct_iio_channel, attr string, val int64) error {
	if ch == nil {
		return fmt.Errorf("pluto: channel missing for attr %s", attr)
	}
	cAttr := C.CString(attr)
	defer C.free(unsafe.Pointer(cAttr))
	ret := C.iio_channel_attr_write_longlong(ch, cAttr, C.longlong(val))
	if ret < 0 {
		return fmt.Errorf("pluto: write attr %s failed (rc=%d)", attr, int(ret))
	}
	return nil
}