configcenter/pkg/sdk/go/client.go

// Package configsdk provides a concurrency-safe Config Center client with
// full-snapshot synchronization and an optional local-file fallback cache.
package configsdk

import (
	"bufio"
	"context"
	"crypto/tls"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"path/filepath"
	"strconv"
	"strings"
	"sync"
	"time"

	"google.golang.org/grpc"
	"google.golang.org/grpc/credentials"
	"google.golang.org/grpc/metadata"

	configcenterv1 "github.com/longpeng/configcenter/pkg/proto/v1"
)

type Options struct {
	BaseURL    string
	Env        string
	App        string
	Token      string
	IP         string
	Instance   string
	CacheFile  string
	HTTPClient *http.Client
}

type GRPCOptions struct {
	Target      string
	Env         string
	App         string
	Token       string
	IP          string
	Instance    string
	CacheFile   string
	DialOptions []grpc.DialOption
}

type Client struct {
	baseURL   string
	env       string
	app       string
	token     string
	ip        string
	instance  string
	cacheFile string
	http      *http.Client
	grpcConn  *grpc.ClientConn
	grpc      configcenterv1.ConfigServiceClient

	mu        sync.RWMutex
	cache     map[string]map[string]string
	revisions map[string]int64
}

type apiEnvelope struct {
	Data json.RawMessage `json:"data"`
}

type runtimeConfig struct {
	Items          map[string]string `json:"items"`
	Revision       int64             `json:"revision"`
	ReleaseVersion int               `json:"releaseVersion"`
}

type configEvent struct {
	Type     string            `json:"type"`
	Items    map[string]string `json:"items"`
	Revision int64             `json:"revision"`
}

type diskCache struct {
	Namespaces map[string]map[string]string `json:"namespaces"`
	Revisions  map[string]int64             `json:"revisions"`
}

func New(options Options) (*Client, error) {
	if strings.TrimSpace(options.BaseURL) == "" || strings.TrimSpace(options.Env) == "" || strings.TrimSpace(options.App) == "" {
		return nil, errors.New("base URL, environment and application are required")
	}
	httpClient := options.HTTPClient
	if httpClient == nil {
		httpClient = &http.Client{Timeout: 15 * time.Second}
	}
	client := &Client{
		baseURL:   strings.TrimRight(options.BaseURL, "/"),
		env:       strings.TrimSpace(options.Env),
		app:       strings.TrimSpace(options.App),
		token:     strings.TrimSpace(options.Token),
		ip:        strings.TrimSpace(options.IP),
		instance:  strings.TrimSpace(options.Instance),
		cacheFile: options.CacheFile,
		http:      httpClient,
		cache:     make(map[string]map[string]string),
		revisions: make(map[string]int64),
	}
	if options.CacheFile != "" {
		if err := client.loadDiskCache(); err != nil && !errors.Is(err, os.ErrNotExist) {
			return nil, fmt.Errorf("load config cache: %w", err)
		}
	}
	return client, nil
}

func NewGRPC(options GRPCOptions) (*Client, error) {
	if strings.TrimSpace(options.Target) == "" || strings.TrimSpace(options.Env) == "" || strings.TrimSpace(options.App) == "" {
		return nil, errors.New("gRPC target, environment and application are required")
	}
	dialOptions := append([]grpc.DialOption(nil), options.DialOptions...)
	if len(dialOptions) == 0 {
		dialOptions = append(dialOptions, grpc.WithTransportCredentials(credentials.NewTLS(&tls.Config{MinVersion: tls.VersionTLS12})))
	}
	connection, err := grpc.NewClient(strings.TrimSpace(options.Target), dialOptions...)
	if err != nil {
		return nil, fmt.Errorf("connect config center gRPC: %w", err)
	}
	client := &Client{
		env:       strings.TrimSpace(options.Env),
		app:       strings.TrimSpace(options.App),
		token:     strings.TrimSpace(options.Token),
		ip:        strings.TrimSpace(options.IP),
		instance:  strings.TrimSpace(options.Instance),
		cacheFile: options.CacheFile,
		grpcConn:  connection,
		grpc:      configcenterv1.NewConfigServiceClient(connection),
		cache:     make(map[string]map[string]string),
		revisions: make(map[string]int64),
	}
	if options.CacheFile != "" {
		if err := client.loadDiskCache(); err != nil && !errors.Is(err, os.ErrNotExist) {
			_ = connection.Close()
			return nil, fmt.Errorf("load config cache: %w", err)
		}
	}
	return client, nil
}

func (c *Client) Close() error {
	if c.grpcConn != nil {
		return c.grpcConn.Close()
	}
	return nil
}

func (c *Client) GetString(namespace, key, fallback string) string {
	c.mu.RLock()
	defer c.mu.RUnlock()
	if items, ok := c.cache[namespace]; ok {
		if value, exists := items[key]; exists {
			return value
		}
	}
	return fallback
}

func (c *Client) GetInt(namespace, key string, fallback int) int {
	value := c.GetString(namespace, key, "")
	parsed, err := strconv.Atoi(value)
	if err != nil {
		return fallback
	}
	return parsed
}

func (c *Client) GetBool(namespace, key string, fallback bool) bool {
	value := c.GetString(namespace, key, "")
	parsed, err := strconv.ParseBool(value)
	if err != nil {
		return fallback
	}
	return parsed
}

func (c *Client) Snapshot(namespace string) map[string]string {
	c.mu.RLock()
	defer c.mu.RUnlock()
	return clone(c.cache[namespace])
}

func (c *Client) Load(ctx context.Context, namespace string) error {
	if c.grpc != nil {
		return c.loadGRPC(ctx, namespace)
	}
	endpoint := c.endpoint("/v1/config", namespace)
	request, err := http.NewRequestWithContext(ctx, http.MethodGet, endpoint, nil)
	if err != nil {
		return err
	}
	c.authorize(request)
	response, err := c.http.Do(request)
	if err != nil {
		return err
	}
	defer func() { _ = response.Body.Close() }()
	if response.StatusCode != http.StatusOK {
		return responseError(response)
	}
	var envelope apiEnvelope
	if err := json.NewDecoder(response.Body).Decode(&envelope); err != nil {
		return err
	}
	var current runtimeConfig
	if err := json.Unmarshal(envelope.Data, &current); err != nil {
		return err
	}
	return c.apply(namespace, current.Items, current.Revision)
}

// WatchAndSync blocks until ctx is canceled. It reconnects with exponential
// backoff and replaces the namespace cache only with complete snapshots.
func (c *Client) WatchAndSync(ctx context.Context, namespace string) error {
	backoff := time.Second
	for {
		err := c.watchOnce(ctx, namespace)
		if ctx.Err() != nil {
			return nil
		}
		if err == nil {
			backoff = time.Second
		}
		timer := time.NewTimer(backoff)
		select {
		case <-ctx.Done():
			timer.Stop()
			return nil
		case <-timer.C:
		}
		if backoff < 30*time.Second {
			backoff *= 2
		}
	}
}

func (c *Client) watchOnce(ctx context.Context, namespace string) error {
	if c.grpc != nil {
		return c.watchGRPCOnce(ctx, namespace)
	}
	request, err := http.NewRequestWithContext(ctx, http.MethodGet, c.endpoint("/v1/watch", namespace), nil)
	if err != nil {
		return err
	}
	request.Header.Set("Accept", "text/event-stream")
	c.authorize(request)
	response, err := c.http.Do(request)
	if err != nil {
		return err
	}
	defer func() { _ = response.Body.Close() }()
	if response.StatusCode != http.StatusOK {
		return responseError(response)
	}
	scanner := bufio.NewScanner(response.Body)
	scanner.Buffer(make([]byte, 64*1024), 10*1024*1024)
	var data strings.Builder
	for scanner.Scan() {
		line := scanner.Text()
		if line == "" {
			if data.Len() > 0 {
				var event configEvent
				if err := json.Unmarshal([]byte(data.String()), &event); err != nil {
					return err
				}
				if err := c.apply(namespace, event.Items, event.Revision); err != nil {
					return err
				}
				data.Reset()
			}
			continue
		}
		if strings.HasPrefix(line, "data:") {
			if data.Len() > 0 {
				data.WriteByte('\n')
			}
			data.WriteString(strings.TrimSpace(strings.TrimPrefix(line, "data:")))
		}
	}
	if err := scanner.Err(); err != nil {
		return err
	}
	return io.EOF
}

func (c *Client) loadGRPC(ctx context.Context, namespace string) error {
	response, err := c.grpc.GetConfig(c.grpcContext(ctx), &configcenterv1.GetConfigRequest{
		Env: c.env, App: c.app, Namespace: namespace, Ip: c.ip, Instance: c.instance,
	})
	if err != nil {
		return err
	}
	return c.apply(namespace, protoItemMap(response.GetItems()), response.GetRevision())
}

func (c *Client) watchGRPCOnce(ctx context.Context, namespace string) error {
	c.mu.RLock()
	lastRevision := c.revisions[namespace]
	c.mu.RUnlock()
	startRevision := int64(0)
	if lastRevision > 0 {
		startRevision = lastRevision + 1
	}
	stream, err := c.grpc.WatchConfig(c.grpcContext(ctx), &configcenterv1.WatchConfigRequest{
		Env: c.env, App: c.app, Namespace: namespace, StartRevision: startRevision, Ip: c.ip, Instance: c.instance,
	})
	if err != nil {
		return err
	}
	for {
		event, err := stream.Recv()
		if err != nil {
			return err
		}
		if err := c.apply(namespace, protoItemMap(event.GetItems()), event.GetRevision()); err != nil {
			return err
		}
	}
}

func (c *Client) grpcContext(ctx context.Context) context.Context {
	if c.token == "" {
		return ctx
	}
	return metadata.AppendToOutgoingContext(ctx, "authorization", "Bearer "+c.token)
}

func protoItemMap(items []*configcenterv1.ConfigItem) map[string]string {
	result := make(map[string]string, len(items))
	for _, item := range items {
		result[item.GetKey()] = item.GetValue()
	}
	return result
}

func (c *Client) endpoint(path, namespace string) string {
	query := url.Values{"env": {c.env}, "app": {c.app}, "namespace": {namespace}}
	if c.ip != "" {
		query.Set("ip", c.ip)
	}
	if c.instance != "" {
		query.Set("instance", c.instance)
	}
	return c.baseURL + path + "?" + query.Encode()
}

func (c *Client) authorize(request *http.Request) {
	if c.token != "" {
		request.Header.Set("Authorization", "Bearer "+c.token)
	}
}

func (c *Client) apply(namespace string, items map[string]string, revision int64) error {
	c.mu.Lock()
	if revision > 0 && revision < c.revisions[namespace] {
		c.mu.Unlock()
		return nil
	}
	c.cache[namespace] = clone(items)
	c.revisions[namespace] = revision
	err := c.saveDiskCacheLocked()
	c.mu.Unlock()
	return err
}

func (c *Client) loadDiskCache() error {
	payload, err := os.ReadFile(c.cacheFile)
	if err != nil {
		return err
	}
	var cached diskCache
	if err := json.Unmarshal(payload, &cached); err != nil {
		return err
	}
	if cached.Namespaces != nil {
		c.cache = cached.Namespaces
	}
	if cached.Revisions != nil {
		c.revisions = cached.Revisions
	}
	return nil
}

func (c *Client) saveDiskCacheLocked() error {
	if c.cacheFile == "" {
		return nil
	}
	payload, err := json.MarshalIndent(diskCache{Namespaces: c.cache, Revisions: c.revisions}, "", "  ")
	if err != nil {
		return err
	}
	directory := filepath.Dir(c.cacheFile)
	if err := os.MkdirAll(directory, 0o700); err != nil {
		return err
	}
	temporary, err := os.CreateTemp(directory, ".configcenter-cache-*")
	if err != nil {
		return err
	}
	temporaryName := temporary.Name()
	defer os.Remove(temporaryName) //nolint:errcheck
	defer func() { _ = temporary.Close() }()
	if err := temporary.Chmod(0o600); err != nil {
		return err
	}
	if _, err := temporary.Write(payload); err != nil {
		return err
	}
	if err := temporary.Sync(); err != nil {
		return err
	}
	if err := temporary.Close(); err != nil {
		return err
	}
	return os.Rename(temporaryName, c.cacheFile)
}

func responseError(response *http.Response) error {
	payload, _ := io.ReadAll(io.LimitReader(response.Body, 64*1024))
	return fmt.Errorf("config center returned %s: %s", response.Status, strings.TrimSpace(string(payload)))
}

func clone(input map[string]string) map[string]string {
	result := make(map[string]string, len(input))
	for key, value := range input {
		result[key] = value
	}
	return result
}