package client

import (
	"fmt"
	"sync/atomic"
	"time"

	"github.com/theater/picomap/lib/halfsiphash"
	"github.com/theater/picomap/lib/msgpack"
	"io"
)

var HashKey = [8]byte{}

type transport interface {
	Send(data []byte) error
	SetReadTimeout(timeout time.Duration)
	Reader() io.Reader
	Close() error
}

type Client struct {
	transport transport
	timeout   time.Duration
	nextID    atomic.Uint32
}

func (c *Client) Close() error {
	return c.transport.Close()
}

func (c *Client) send(msg any) (uint32, error) {
	id := c.nextID.Add(1)
	payload, err := msgpack.Marshal(msg)
	if err != nil {
		return 0, fmt.Errorf("encode inner: %w", err)
	}
	checksum := halfsiphash.Sum32(payload, HashKey)
	env := Envelope{MessageID: id, Checksum: checksum, Payload: payload}
	data, err := msgpack.Marshal(&env)
	if err != nil {
		return 0, fmt.Errorf("encode envelope: %w", err)
	}
	return id, c.transport.Send(data)
}

func (c *Client) receive(expectedID uint32) (any, error) {
	c.transport.SetReadTimeout(c.timeout)
	dec := msgpack.NewDecoder(c.transport.Reader())
	var env Envelope
	if err := dec.Decode(&env); err != nil {
		return nil, fmt.Errorf("decode envelope: %w", err)
	}
	if env.MessageID != expectedID {
		return nil, fmt.Errorf("message id mismatch: got %d, want %d", env.MessageID, expectedID)
	}
	expected := halfsiphash.Sum32(env.Payload, HashKey)
	if env.Checksum != expected {
		return nil, fmt.Errorf("checksum mismatch: got %08x, want %08x", env.Checksum, expected)
	}
	var inner any
	if err := msgpack.Unmarshal(env.Payload, &inner); err != nil {
		return nil, fmt.Errorf("decode inner: %w", err)
	}
	if devErr, ok := inner.(*DeviceError); ok {
		return nil, devErr
	}
	return inner, nil
}

func roundTrip[T any](c *Client, req any) (*T, error) {
	id, err := c.send(req)
	if err != nil {
		return nil, err
	}
	resp, err := c.receive(id)
	if err != nil {
		return nil, err
	}
	typed, ok := resp.(*T)
	if !ok {
		return nil, fmt.Errorf("unexpected response: %T", resp)
	}
	return typed, nil
}

func (c *Client) PICOBOOT() error {
	_, err := roundTrip[ResponsePICOBOOT](c, &RequestPICOBOOT{})
	return err
}

func (c *Client) Info() (*ResponseInfo, error) {
	return roundTrip[ResponseInfo](c, &RequestInfo{})
}