package notify

import (
	"sync"
	"time"
)

// maxAlertHistory is the maximum number of alerts to retain.
const maxAlertHistory = 100

// AlertEntry represents a single notification that was sent.
type AlertEntry struct {
	Timestamp time.Time
	Title     string
	Message   string
	Priority  string
}

// AlertHistory is a thread-safe ring buffer that stores
// the most recent alerts.
type AlertHistory struct {
	mu      sync.RWMutex
	entries [maxAlertHistory]AlertEntry
	count   int
	index   int
}

// NewAlertHistory creates a new empty AlertHistory.
func NewAlertHistory() *AlertHistory {
	return &AlertHistory{}
}

// Add records a new alert entry in the ring buffer.
func (h *AlertHistory) Add(entry AlertEntry) {
	h.mu.Lock()
	defer h.mu.Unlock()

	h.entries[h.index] = entry
	h.index = (h.index + 1) % maxAlertHistory

	if h.count < maxAlertHistory {
		h.count++
	}
}

// Recent returns the stored alerts in reverse chronological
// order (newest first). Returns at most maxAlertHistory entries.
func (h *AlertHistory) Recent() []AlertEntry {
	h.mu.RLock()
	defer h.mu.RUnlock()

	result := make([]AlertEntry, h.count)

	for i := range h.count {
		// Walk backwards from the most recent entry.
		idx := (h.index - 1 - i + maxAlertHistory) %
			maxAlertHistory
		result[i] = h.entries[idx]
	}

	return result
}