package loki

import (
	"net/http"
	"regexp"
	"sync"
	"time"
)

const logEntriesChanSize = 5000

// Represents a single log entry.
type logEntry struct {
	Ts   time.Time `json:"ts"`
	Line string    `json:"line"`
}

type labels map[string]string

// Stream represents a stream of log entries with associated labels.
type stream struct {
	Labels  labels     `json:"-"`
	Entries []logEntry `json:"entries"`
}

type promtailMsg struct {
	Streams []stream `json:"streams"`
}

// Client is a client for sending log entries.
type Client struct {
	config         Config
	quit           chan struct{}
	entries        chan logEntry
	waitGroup      sync.WaitGroup
	client         http.Client
	missedMessages int64
	mutex          sync.RWMutex
}

type Config struct {
	Enabled bool
	// E.g. localhost:3100/api/prom/push.
	Endpoint string
	Labels   map[string]string
	// Maximum message buffering time.
	BatchWait time.Duration
	// Maximum number of messages in the queue.
	BatchEntriesNumber int
}

// Setup initializes the client with the given configuration and starts the processing goroutine.
// It is the caller's responsibility to call Shutdown() to free resources.
func Setup(conf Config) *Client {
	client := newClient()
	client.config = conf
	client.config.Endpoint = normalizeURL(client.config.Endpoint)
	go client.run()
	return client
}

// Shutdown stops the client and waits for all logs to be sent.
func (client *Client) Shutdown() {
	client.mutex.Lock()
	client.config.Enabled = false
	client.mutex.Unlock()

	close(client.quit)
	client.waitGroup.Wait()
}

// IsEnabled checks whether the client is enabled.
func (client *Client) IsEnabled() bool {
	client.mutex.RLock()
	defer client.mutex.RUnlock()
	return client.config.Enabled
}

func newClient() *Client {
	return &Client{
		quit:      make(chan struct{}),
		entries:   make(chan logEntry, logEntriesChanSize),
		client:    http.Client{},
		config:    Config{Enabled: false},
		mutex:     sync.RWMutex{},
		waitGroup: sync.WaitGroup{},
	}
}

func normalizeURL(host string) string {
	if !regexp.MustCompile(`^https?:\/\/`).MatchString(host) {
		host = "http://" + host
	}

	return host
}