event-driven-shoppinglist/example_client.go

package main

import (
	"bytes"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"time"
)

// ExampleClient demonstrates how to interact with the event store API
type ExampleClient struct {
	baseURL string
	client  *http.Client
}

func NewExampleClient(baseURL string) *ExampleClient {
	return &ExampleClient{
		baseURL: baseURL,
		client:  &http.Client{Timeout: 10 * time.Second},
	}
}

func (c *ExampleClient) CreateItem(itemID, content string) error {
	// Create item using JSON Patch "add" operations
	patches := []PatchOperation{
		{Op: "add", Path: "/content", Value: content},
	}

	return c.sendPatch("shopping_items", itemID, patches)
}

func (c *ExampleClient) UpdateItem(itemID, content string) error {
	// Update item using JSON Patch "replace" operation
	patches := []PatchOperation{
		{Op: "replace", Path: "/content", Value: content},
	}

	return c.sendPatch("shopping_items", itemID, patches)
}

func (c *ExampleClient) DeleteItem(itemID string) error {
	// Delete item using JSON Patch "add" operation for deleted_at
	patches := []PatchOperation{
		{Op: "add", Path: "/deleted_at", Value: time.Now()},
	}

	return c.sendPatch("shopping_items", itemID, patches)
}

// sendPatch sends JSON Patch operations using the PATCH method
func (c *ExampleClient) sendPatch(collection, itemID string, patches []PatchOperation) error {
	jsonData, err := json.Marshal(patches)
	if err != nil {
		return fmt.Errorf("failed to marshal patches: %w", err)
	}

	url := fmt.Sprintf("%s/api/collections/%s/items/%s", c.baseURL, collection, itemID)
	req, err := http.NewRequest("PATCH", url, bytes.NewBuffer(jsonData))
	if err != nil {
		return fmt.Errorf("failed to create request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := c.client.Do(req)
	if err != nil {
		return fmt.Errorf("failed to send patch: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("patch failed: %s", string(body))
	}

	return nil
}

// sendEvent sends event using the legacy POST method
func (c *ExampleClient) sendEvent(event Event) error {
	jsonData, err := json.Marshal(event)
	if err != nil {
		return fmt.Errorf("failed to marshal event: %w", err)
	}

	resp, err := c.client.Post(c.baseURL+"/api/events", "application/json", bytes.NewBuffer(jsonData))
	if err != nil {
		return fmt.Errorf("failed to send event: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusCreated {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("event creation failed: %s", string(body))
	}

	return nil
}

func (c *ExampleClient) SyncEvents(lastSeq int, lastHash string) (*SyncResponse, error) {
	syncReq := SyncRequest{
		LastSeq:  lastSeq,
		LastHash: lastHash,
	}

	jsonData, err := json.Marshal(syncReq)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal sync request: %w", err)
	}

	resp, err := c.client.Post(c.baseURL+"/api/sync", "application/json", bytes.NewBuffer(jsonData))
	if err != nil {
		return nil, fmt.Errorf("failed to sync: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("sync failed: %s", string(body))
	}

	var syncResp SyncResponse
	if err := json.NewDecoder(resp.Body).Decode(&syncResp); err != nil {
		return nil, fmt.Errorf("failed to decode sync response: %w", err)
	}

	return &syncResp, nil
}

func (c *ExampleClient) GetItems(collection string) ([]map[string]interface{}, error) {
	resp, err := c.client.Get(c.baseURL + "/api/items/" + collection)
	if err != nil {
		return nil, fmt.Errorf("failed to get items: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return nil, fmt.Errorf("get items failed: %s", string(body))
	}

	var result map[string]interface{}
	if err := json.NewDecoder(resp.Body).Decode(&result); err != nil {
		return nil, fmt.Errorf("failed to decode response: %w", err)
	}

	items, ok := result["items"].([]interface{})
	if !ok {
		return nil, fmt.Errorf("invalid response format")
	}

	var typedItems []map[string]interface{}
	for _, item := range items {
		if typedItem, ok := item.(map[string]interface{}); ok {
			typedItems = append(typedItems, typedItem)
		}
	}

	return typedItems, nil
}

// Advanced JSON Patch operations examples
func (c *ExampleClient) AdvancedPatchExample(itemID string) error {
	// Example: Create item with multiple fields
	patches := []PatchOperation{
		{Op: "add", Path: "/content", Value: "Advanced Shopping Item"},
		{Op: "add", Path: "/quantity", Value: 5},
		{Op: "add", Path: "/tags", Value: []string{"grocery", "urgent"}},
		{Op: "add", Path: "/metadata", Value: map[string]interface{}{
			"store":    "SuperMart",
			"category": "food",
		}},
	}

	if err := c.sendPatch("shopping_items", itemID, patches); err != nil {
		return fmt.Errorf("failed to create advanced item: %w", err)
	}

	// Example: Complex updates using different operations
	updatePatches := []PatchOperation{
		{Op: "replace", Path: "/quantity", Value: 3},                // Update quantity
		{Op: "add", Path: "/tags/-", Value: "sale"},                 // Append to array
		{Op: "replace", Path: "/metadata/store", Value: "MegaMart"}, // Update nested field
		{Op: "add", Path: "/metadata/priority", Value: "high"},      // Add new nested field
		{Op: "remove", Path: "/tags/0"},                             // Remove first tag
	}

	return c.sendPatch("shopping_items", itemID, updatePatches)
}

// Example usage function
func runClientExample() {
	client := NewExampleClient("http://localhost:8090")

	fmt.Println("=== RFC6902 JSON Patch Event Store Example ===")

	// Create some shopping items using JSON Patch
	fmt.Println("Creating shopping items with JSON Patch...")
	if err := client.CreateItem("item1", "Milk"); err != nil {
		fmt.Printf("Error creating item1: %v\n", err)
		return
	}

	if err := client.CreateItem("item2", "Bread"); err != nil {
		fmt.Printf("Error creating item2: %v\n", err)
		return
	}

	// Update an item using JSON Patch replace
	fmt.Println("Updating item1 with JSON Patch replace...")
	if err := client.UpdateItem("item1", "Organic Milk"); err != nil {
		fmt.Printf("Error updating item1: %v\n", err)
		return
	}

	// Advanced JSON Patch operations
	fmt.Println("Demonstrating advanced JSON Patch operations...")
	if err := client.AdvancedPatchExample("item3"); err != nil {
		fmt.Printf("Error with advanced patch example: %v\n", err)
		return
	}

	// Get current items
	fmt.Println("Fetching current items...")
	items, err := client.GetItems("shopping_items")
	if err != nil {
		fmt.Printf("Error getting items: %v\n", err)
		return
	}

	fmt.Printf("Current items: %+v\n", items)

	// Sync events (simulate client sync)
	fmt.Println("Syncing events...")
	syncResp, err := client.SyncEvents(0, "")
	if err != nil {
		fmt.Printf("Error syncing: %v\n", err)
		return
	}

	fmt.Printf("Sync response - Found %d events\n", len(syncResp.Events))

	// Soft delete an item using JSON Patch
	fmt.Println("Soft deleting item2 with JSON Patch...")
	if err := client.DeleteItem("item2"); err != nil {
		fmt.Printf("Error deleting item2: %v\n", err)
		return
	}

	// Get items again to see the change
	fmt.Println("Fetching items after deletion...")
	items, err = client.GetItems("shopping_items")
	if err != nil {
		fmt.Printf("Error getting items: %v\n", err)
		return
	}

	fmt.Printf("Items after deletion: %+v\n", items)
	fmt.Println("=== JSON Patch Example completed ===")
}

// Uncomment the following to run the example:
// func init() {
//     go func() {
//         time.Sleep(2 * time.Second) // Wait for server to start
//         runClientExample()
//     }()
// }