package main

import (
	"encoding/json"
	"fmt"
	"os"
	"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"`
}

// managedSource is the SourceManager's view of one running source.
type managedSource struct {
	id     string
	label  string
	addr   string
	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.
// Returns the source ID.
func (sm *SourceManager) Add(label, addr string) string {
	if label == "" {
		label = addr
	}
	id := sm.genID()
	c := NewUDPClient(addr, id, sm.hub)
	ms := &managedSource{id: id, label: label, addr: addr, 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})
	}
	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)
	}
	return nil
}

// ParseSourceArg parses "label@host:port" or "host:port".
func ParseSourceArg(s string) (label, addr string) {
	s = strings.TrimSpace(s)
	if idx := strings.Index(s, "@"); idx >= 0 {
		return strings.TrimSpace(s[:idx]), strings.TrimSpace(s[idx+1:])
	}
	return "", s
}