package main

import (
	"encoding/json"
	"fmt"
	"os"
	"strconv"
	"strings"
	"sync"
	"sync/atomic"
)

// SourceConfig is the serialisable description of one data source (for file save/load).
type SourceConfig struct {
	Label          string `json:"label"`
	Addr           string `json:"addr"`
	MulticastGroup string `json:"multicastGroup,omitempty"` // "" = unicast mode
	DataPort       int    `json:"dataPort,omitempty"`        // 0 = Addr port+1
}

// managedSource is the SourceManager's view of one running source.
type managedSource struct {
	id             string
	label          string
	addr           string
	multicastGroup string
	dataPort       int
	client         *UDPClient
}

// SourceManager owns the lifecycle of all active data sources.
// It is the only place where UDPClient instances are created and stopped.
type SourceManager struct {
	mu       sync.RWMutex
	sources  map[string]*managedSource
	hub      *Hub
	filePath string // empty = save not configured
	nextID   atomic.Int32
}

// NewSourceManager creates a SourceManager bound to the given hub.
// filePath is the default path for Save(); may be empty.
func NewSourceManager(hub *Hub, filePath string) *SourceManager {
	return &SourceManager{
		sources:  make(map[string]*managedSource),
		hub:      hub,
		filePath: filePath,
	}
}

func (sm *SourceManager) genID() string {
	return fmt.Sprintf("s%d", sm.nextID.Add(1))
}

// Add creates a new source, registers it in the hub, and starts connecting.
// multicastGroup: multicast IP (e.g. "239.0.0.1") or "" for unicast mode.
// dataPort: UDP data port in multicast mode; 0 = Addr port+1.
// Returns the source ID.
func (sm *SourceManager) Add(label, addr, multicastGroup string, dataPort int) string {
	if label == "" {
		label = addr
	}
	id := sm.genID()
	c := NewUDPClient(addr, id, sm.hub, multicastGroup, dataPort)
	ms := &managedSource{
		id: id, label: label, addr: addr,
		multicastGroup: multicastGroup, dataPort: dataPort,
		client: c,
	}

	sm.mu.Lock()
	sm.sources[id] = ms
	sm.mu.Unlock()

	// Register in hub (creates hub-side state, broadcasts sources list).
	sm.hub.AddSource(id, label, addr)
	go c.Run()
	return id
}

// Remove stops the source's client and removes it from the hub.
func (sm *SourceManager) Remove(id string) {
	sm.mu.Lock()
	ms, ok := sm.sources[id]
	if ok {
		delete(sm.sources, id)
	}
	sm.mu.Unlock()

	if ok {
		ms.client.Stop()
		sm.hub.RemoveSource(id)
	}
}

// Save writes the current source list to filePath.
func (sm *SourceManager) Save() error {
	if sm.filePath == "" {
		return fmt.Errorf("no sources-file configured (start with --sources-file path)")
	}
	sm.mu.RLock()
	cfgs := make([]SourceConfig, 0, len(sm.sources))
	for _, ms := range sm.sources {
		cfgs = append(cfgs, SourceConfig{
			Label:          ms.label,
			Addr:           ms.addr,
			MulticastGroup: ms.multicastGroup,
			DataPort:       ms.dataPort,
		})
	}
	sm.mu.RUnlock()

	data, err := json.MarshalIndent(cfgs, "", "  ")
	if err != nil {
		return err
	}
	return os.WriteFile(sm.filePath, data, 0644)
}

// Load reads sources from path and adds them. Sets filePath for future saves.
func (sm *SourceManager) Load(path string) error {
	data, err := os.ReadFile(path)
	if err != nil {
		return err
	}
	var cfgs []SourceConfig
	if err := json.Unmarshal(data, &cfgs); err != nil {
		return err
	}
	sm.filePath = path
	for _, cfg := range cfgs {
		sm.Add(cfg.Label, cfg.Addr, cfg.MulticastGroup, cfg.DataPort)
	}
	return nil
}

// ParseSourceArg parses "label@host:port" or "host:port".
func ParseSourceArg(s string) (label, addr string) {
	label, addr, _, _ = ParseSourceArgFull(s)
	return
}

// ParseSourceArgFull parses "[label@]host:port[/multicastGroup:dataPort]".
// Examples:
//
//	"Streamer@127.0.0.1:44500/239.0.0.1:44503"  → label="Streamer", addr="127.0.0.1:44500", group="239.0.0.1", port=44503
//	"127.0.0.1:44501"                            → label="", addr="127.0.0.1:44501", group="", port=0
func ParseSourceArgFull(s string) (label, addr, multicastGroup string, dataPort int) {
	s = strings.TrimSpace(s)
	rest := s
	if idx := strings.Index(s, "@"); idx >= 0 {
		label = strings.TrimSpace(s[:idx])
		rest = strings.TrimSpace(s[idx+1:])
	}
	if idx := strings.Index(rest, "/"); idx >= 0 {
		addr = strings.TrimSpace(rest[:idx])
		mcastPart := strings.TrimSpace(rest[idx+1:])
		if lastColon := strings.LastIndex(mcastPart, ":"); lastColon >= 0 {
			multicastGroup = strings.TrimSpace(mcastPart[:lastColon])
			dataPort, _ = strconv.Atoi(strings.TrimSpace(mcastPart[lastColon+1:]))
		} else {
			multicastGroup = mcastPart
		}
	} else {
		addr = rest
	}
	return
}