# Server \[Protect endpoints with payment requirements] Create a payment handler with `server.New()` and use `ChargeMiddleware` or call `Charge()` directly. The `charge.NewMethod` factory configures `Currency` and `Recipient` once, then every charge uses those defaults. ## Quick start ```go [server.go] import ( "github.com/tempoxyz/mpp-go/pkg/server" charge "github.com/tempoxyz/mpp-go/pkg/tempo/server" ) intent, _ := charge.NewIntent(charge.IntentConfig{ RPCURL: "https://rpc.tempo.xyz", }) method := charge.NewMethod(charge.MethodConfig{ Intent: intent, Recipient: "0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266", }) payment := server.New(method, "api.example.com", "my-server-secret") result, err := payment.Charge(ctx, server.ChargeParams{ Authorization: r.Header.Get("Authorization"), Amount: "0.50", }) if result.IsChallenge() { server.WriteChallenge(w, result.Challenge, payment.Realm()) return } // result.Receipt is the verified Receipt ``` ## Framework middleware ### net/http Use `server.ChargeMiddleware` to wrap any `http.Handler`: ```go mux := http.NewServeMux() mux.Handle("/resource", server.ChargeMiddleware(payment, server.ChargeParams{ Amount: "0.50", Description: "Paid resource", })(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) { credential := server.CredentialFromContext(r.Context()) json.NewEncoder(w).Encode(map[string]any{ "data": "paid content", "payer": credential.Source, }) }))) ``` ### Gin Use `ginadapter.ChargeMiddleware` from `pkg/server/gin`: ```go import ginadapter "github.com/tempoxyz/mpp-go/pkg/server/gin" r := gin.Default() r.GET("/resource", ginadapter.ChargeMiddleware(payment, server.ChargeParams{ Amount: "0.50", }), func(c *gin.Context) { credential := server.CredentialFromContext(c.Request.Context()) c.JSON(200, gin.H{"payer": credential.Source}) }) ``` ### Echo Use `echoadapter.ChargeMiddleware` from `pkg/server/echo`: ```go import echoadapter "github.com/tempoxyz/mpp-go/pkg/server/echo" e := echo.New() e.GET("/resource", func(c echo.Context) error { credential := server.CredentialFromContext(c.Request().Context()) return c.JSON(200, map[string]any{"payer": credential.Source}) }, echoadapter.ChargeMiddleware(payment, server.ChargeParams{ Amount: "0.50", })) ``` ### Chi Use `server.ChargeMiddleware` with `chi.With`: ```go r := chi.NewRouter() r.With(server.ChargeMiddleware(payment, server.ChargeParams{ Amount: "0.50", })).Get("/resource", func(w http.ResponseWriter, r *http.Request) { credential := server.CredentialFromContext(r.Context()) json.NewEncoder(w).Encode(map[string]any{"payer": credential.Source}) }) ``` ## `MethodConfig` parameters ### ChainID (optional) * **Type:** `int64` Explicitly bind issued Challenges to a specific chain. If omitted, `mpp-go` infers it from `IntentConfig.RPCURL` when it matches a known Tempo RPC endpoint. ### Currency (optional) * **Type:** `string` * **Default:** USDC.e on mainnet, pathUSD on testnet TIP-20 token address for charges. ### Decimals (optional) * **Type:** `int` * **Default:** `6` Token decimal places for dollar-to-base-unit conversion. ### FeePayer (optional) * **Type:** `bool` * **Default:** `false` Enable fee sponsorship for all Challenges. When enabled, the server co-signs and sponsors transaction gas fees. ### FeePayerURL (optional) * **Type:** `string` URL of a remote co-signer when the server does not sign locally. ### Intent * **Type:** `*charge.Intent` Intent instance created by `charge.NewIntent`. ### Memo (optional) * **Type:** `string` Default memo attached to Challenges. ### Recipient (optional) * **Type:** `string` Default recipient address for charges. ### SupportedModes (optional) * **Type:** `[]tempo.ChargeMode` Supported Credential submission modes (for example, `pull`, `push`). ## `IntentConfig` parameters ### FeePayerPrivateKey (optional) * **Type:** `string` Hex-encoded private key for fee sponsorship. The server co-signs and sponsors transaction gas fees. ### FeePayerSigner (optional) * **Type:** `*temposigner.Signer` Custom signer for fee sponsorship. Takes precedence over `FeePayerPrivateKey`. ### RPC (optional) * **Type:** `tempo.RPCClient` Custom RPC client instance. Takes precedence over `RPCURL`. ### RPCURL (optional) * **Type:** `string` * **Default:** `"https://rpc.tempo.xyz"` Tempo RPC endpoint URL. ### Store (optional) * **Type:** `tempo.Store` Replay-protection store for hash and proof Credentials. Defaults to an in-memory store. ## `ChargeParams` parameters ### Amount * **Type:** `string` Payment amount in dollars (for example, `"0.50"` for $0.50). Automatically converted to base units using the configured decimals. ### Authorization (optional) * **Type:** `string` The `Authorization` header value from the incoming request. ### ChainID (optional) * **Type:** `int64` Override the method's default chain ID for this charge. ### Currency (optional) * **Type:** `string` Override the method's default currency address. ### Description (optional) * **Type:** `string` Human-readable description attached to the Challenge. ### Expires (optional) * **Type:** `string` Challenge expiration as ISO 8601 timestamp. Defaults to 5 minutes from now. ### ExternalID (optional) * **Type:** `string` Merchant reference ID for reconciliation. ### FeePayer (optional) * **Type:** `bool` Override the method's default fee sponsorship setting for this charge. ### FeePayerURL (optional) * **Type:** `string` Override the method's default fee payer URL for this charge. ### Memo (optional) * **Type:** `string` Memo attached to this Challenge. ### Meta (optional) * **Type:** `map[string]string` Arbitrary metadata attached to the Challenge. ### Recipient (optional) * **Type:** `string` Override the method's default recipient address. ### Splits (optional) * **Type:** `[]tempo.SplitParams` Split the payment across multiple recipients. ### SupportedModes (optional) * **Type:** `[]tempo.ChargeMode` Override supported submission modes for this charge. ## Fee sponsorship Sponsor gas fees so clients do not need native tokens. Pass `FeePayerPrivateKey` in the `IntentConfig`: ```go intent, _ := charge.NewIntent(charge.IntentConfig{ RPCURL: "https://rpc.tempo.xyz", FeePayerPrivateKey: os.Getenv("FEE_PAYER_KEY"), }) method := charge.NewMethod(charge.MethodConfig{ Intent: intent, Recipient: "0xf39Fd6e51aad88F6F4ce6aB8827279cffFb92266", }) ``` When fee sponsorship is enabled, the server co-signs transactions and covers gas fees on behalf of the client. ## Context helpers | Function | Description | |----------|-------------| | `CredentialFromContext(ctx)` | Extract the verified Credential from request context | | `ReceiptFromContext(ctx)` | Extract the verified Receipt from request context | | `ContextWithPayment(ctx, credential, receipt)` | Store payment data in context | ## Key types | Type | Description | |------|-------------| | `ChargeParams` | Parameters for a single charge | | `IntentConfig` | Configuration for `charge.NewIntent` | | `MethodConfig` | Configuration for `charge.NewMethod` | | `Mpp` | Server handler binding method, realm, and secret | | `ChargeResult` | Charge result containing either a Challenge or a Receipt | | `SplitParams` | Payment split recipient and amount |