// Package scpi implements a SCPI instrument data source. Each configured
// instrument is reached over a raw TCP socket (line-based SCPI, the "SCPI raw" /
// port 5025 convention); a VXI-11 transport is reserved for later. Channels are
// exposed as signals named "instrument:channel" and polled at a configurable
// interval. Channels with a write_cmd template accept Write.
package scpi

import (
	"context"
	"fmt"
	"strconv"
	"strings"
	"time"

	"github.com/uopi/uopi/internal/datasource"
)

const defaultPollInterval = time.Second

type instrumentConn struct {
	inst Instrument
	tr   transport
}

// Scpi is a datasource.DataSource backed by one or more SCPI instruments.
type Scpi struct {
	pollInterval time.Duration
	instruments  map[string]*instrumentConn
	signals      map[string]signalRef // "instrument:channel" → ref
}

type signalRef struct {
	instrument string
	ch         Channel
}

// New builds a SCPI source from config. It does not dial; connections are
// established lazily on first poll/write.
func New(cfg Config) (*Scpi, error) {
	poll := time.Duration(cfg.PollIntervalMs) * time.Millisecond
	if poll <= 0 {
		poll = defaultPollInterval
	}
	s := &Scpi{
		pollInterval: poll,
		instruments:  make(map[string]*instrumentConn),
		signals:      make(map[string]signalRef),
	}
	for _, inst := range cfg.Instruments {
		if inst.Name == "" || inst.Address == "" {
			return nil, fmt.Errorf("scpi: instrument needs name and address")
		}
		if _, dup := s.instruments[inst.Name]; dup {
			return nil, fmt.Errorf("scpi: duplicate instrument %q", inst.Name)
		}
		tr, err := newTransport(inst)
		if err != nil {
			return nil, err
		}
		ic := &instrumentConn{inst: inst, tr: tr}
		for _, ch := range inst.Channels {
			if ch.Name == "" || ch.Query == "" {
				return nil, fmt.Errorf("scpi: instrument %q channel needs name and query", inst.Name)
			}
			key := inst.Name + ":" + ch.Name
			if _, dup := s.signals[key]; dup {
				return nil, fmt.Errorf("scpi: instrument %q duplicate channel %q", inst.Name, ch.Name)
			}
			s.signals[key] = signalRef{instrument: inst.Name, ch: ch}
		}
		s.instruments[inst.Name] = ic
	}
	return s, nil
}

// newTransport selects the transport implementation for an instrument.
func newTransport(inst Instrument) (transport, error) {
	addr := inst.Address
	switch strings.ToLower(inst.Transport) {
	case "", "raw":
		if !strings.Contains(addr, ":") {
			addr += ":5025"
		}
		return newRawSocket(addr, time.Duration(inst.TimeoutMs)*time.Millisecond, inst.Terminator), nil
	case "vxi11":
		return nil, fmt.Errorf("scpi: vxi11 transport not yet implemented")
	default:
		return nil, fmt.Errorf("scpi: unknown transport %q", inst.Transport)
	}
}

// Name implements datasource.DataSource.
func (s *Scpi) Name() string { return "scpi" }

// Connect is a no-op; connections are dialled lazily per instrument.
func (s *Scpi) Connect(_ context.Context) error { return nil }

// ListSignals returns metadata for every configured channel.
func (s *Scpi) ListSignals(_ context.Context) ([]datasource.Metadata, error) {
	out := make([]datasource.Metadata, 0, len(s.signals))
	for _, ref := range s.signals {
		out = append(out, ref.ch.metadata(ref.instrument))
	}
	return out, nil
}

// GetMetadata returns metadata for one signal.
func (s *Scpi) GetMetadata(_ context.Context, signal string) (datasource.Metadata, error) {
	ref, ok := s.signals[signal]
	if !ok {
		return datasource.Metadata{}, datasource.ErrNotFound
	}
	return ref.ch.metadata(ref.instrument), nil
}

// readSignal performs one synchronous query of a channel.
func (s *Scpi) readSignal(ref signalRef) (datasource.Value, error) {
	ic := s.instruments[ref.instrument]
	resp, err := ic.tr.query(ref.ch.Query)
	if err != nil {
		return datasource.Value{}, err
	}
	data, err := parseValue(ref.ch.dataType(), resp)
	if err != nil {
		return datasource.Value{}, err
	}
	return datasource.Value{Timestamp: time.Now(), Data: data, Quality: datasource.QualityGood}, nil
}

// Subscribe polls the channel at its configured interval (falling back to the
// source default) and pushes values into ch. A query error emits QualityBad and
// polling continues.
func (s *Scpi) Subscribe(ctx context.Context, signal string, ch chan<- datasource.Value) (datasource.CancelFunc, error) {
	ref, ok := s.signals[signal]
	if !ok {
		return nil, datasource.ErrNotFound
	}
	interval := s.pollInterval
	if ref.ch.PollIntervalMs > 0 {
		interval = time.Duration(ref.ch.PollIntervalMs) * time.Millisecond
	}

	ctx, cancel := context.WithCancel(ctx)
	go func() {
		ticker := time.NewTicker(interval)
		defer ticker.Stop()
		emit := func() {
			v, err := s.readSignal(ref)
			if err != nil {
				v = datasource.Value{Timestamp: time.Now(), Quality: datasource.QualityBad}
			}
			select {
			case ch <- v:
			case <-ctx.Done():
			}
		}
		emit()
		for {
			select {
			case <-ticker.C:
				emit()
			case <-ctx.Done():
				return
			}
		}
	}()
	return datasource.CancelFunc(cancel), nil
}

// Write sends the channel's write_cmd template with the value substituted.
func (s *Scpi) Write(_ context.Context, signal string, value any) error {
	ref, ok := s.signals[signal]
	if !ok {
		return datasource.ErrNotFound
	}
	if !ref.ch.writable() {
		return datasource.ErrNotWritable
	}
	ic := s.instruments[ref.instrument]
	cmd := formatWrite(ref.ch.WriteCmd, value)
	return ic.tr.write(cmd)
}

// History is unavailable for SCPI instruments.
func (s *Scpi) History(_ context.Context, _ string, _, _ time.Time, _ int) ([]datasource.Value, error) {
	return nil, datasource.ErrHistoryUnavailable
}

// Close tears down every instrument connection.
func (s *Scpi) Close() {
	for _, ic := range s.instruments {
		ic.tr.close()
	}
}

// formatWrite substitutes value into the write template. A "%" in the template
// is treated as a printf verb; otherwise the value is appended after a space.
func formatWrite(tmpl string, value any) string {
	if strings.Contains(tmpl, "%") {
		return fmt.Sprintf(tmpl, value)
	}
	return fmt.Sprintf("%s %v", tmpl, value)
}

// parseValue converts a raw SCPI response string into the channel's data type.
func parseValue(t datasource.DataType, resp string) (any, error) {
	resp = strings.TrimSpace(resp)
	switch t {
	case datasource.TypeString:
		return resp, nil
	case datasource.TypeInt64:
		// Accept "12", "12.0", or scientific notation by going through float.
		f, err := strconv.ParseFloat(resp, 64)
		if err != nil {
			return nil, fmt.Errorf("scpi: parse int %q: %w", resp, err)
		}
		return int64(f), nil
	case datasource.TypeBool:
		switch strings.ToUpper(resp) {
		case "1", "ON", "TRUE":
			return true, nil
		case "0", "OFF", "FALSE":
			return false, nil
		}
		f, err := strconv.ParseFloat(resp, 64)
		if err != nil {
			return nil, fmt.Errorf("scpi: parse bool %q: %w", resp, err)
		}
		return f != 0, nil
	default:
		f, err := strconv.ParseFloat(resp, 64)
		if err != nil {
			return nil, fmt.Errorf("scpi: parse float %q: %w", resp, err)
		}
		return f, nil
	}
}