feat: add Http effect to C backend

Implement HTTP client using POSIX sockets:
- Http.get(url) - GET request
- Http.post(url, body) - POST request
- Http.put(url, body) - PUT request
- Http.delete(url) - DELETE request

Features:
- Self-contained implementation (no libcurl dependency)
- URL parsing for host, port, and path
- HTTP/1.1 protocol with Connection: close
- Response body extraction

All Http operations use evidence passing for handler customization.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

docs/C_BACKEND.md

@@ -301,11 +301,15 @@ Implemented C versions of:
 
 All effects use evidence passing for handler customization.
 
-### Phase 3: Http Effect
+### Phase 3: Http Effect ✅ COMPLETE
 
-Implement HTTP client:
+HTTP client using POSIX sockets:
 - `Http.get(url)` - GET request
 - `Http.post(url, body)` - POST request
+- `Http.put(url, body)` - PUT request
+- `Http.delete(url)` - DELETE request
+
+Self-contained implementation (no external dependencies like libcurl).
 
 ### Phase 5: JavaScript Backend
 

src/codegen/c_backend.rs

@@ -467,6 +467,15 @@ impl CBackend {
         self.writeln("    void* env;");
         self.writeln("} LuxFileHandler;");
         self.writeln("");
+        self.writeln("// Handler struct for Http effect");
+        self.writeln("typedef struct {");
+        self.writeln("    LuxString (*get)(void* env, LuxString url);");
+        self.writeln("    LuxString (*post)(void* env, LuxString url, LuxString body);");
+        self.writeln("    LuxString (*put)(void* env, LuxString url, LuxString body);");
+        self.writeln("    LuxString (*delete_req)(void* env, LuxString url);");
+        self.writeln("    void* env;");
+        self.writeln("} LuxHttpHandler;");
+        self.writeln("");
         self.writeln("// Evidence struct - passed to effectful functions");
         self.writeln("// Contains pointers to current handlers for each effect type");
         self.writeln("typedef struct {");
@@ -476,6 +485,7 @@ impl CBackend {
         self.writeln("    LuxRandomHandler* random;");
         self.writeln("    LuxTimeHandler* time;");
         self.writeln("    LuxFileHandler* file;");
+        self.writeln("    LuxHttpHandler* http;");
         self.writeln("} LuxEvidence;");
         self.writeln("");
         self.writeln("// Default Console handler using built-in implementations");
@@ -672,6 +682,142 @@ impl CBackend {
         self.writeln("    .env = NULL");
         self.writeln("};");
         self.writeln("");
+        self.writeln("// === Http Effect Built-in Implementations ===");
+        self.writeln("");
+        self.writeln("#include <sys/socket.h>");
+        self.writeln("#include <netinet/in.h>");
+        self.writeln("#include <netdb.h>");
+        self.writeln("#include <arpa/inet.h>");
+        self.writeln("");
+        self.writeln("// Parse URL into host, port, and path");
+        self.writeln("static int lux_http_parse_url(const char* url, char* host, int* port, char* path) {");
+        self.writeln("    *port = 80;");
+        self.writeln("    path[0] = '/'; path[1] = '\\0';");
+        self.writeln("    const char* start = url;");
+        self.writeln("    if (strncmp(url, \"http://\", 7) == 0) start = url + 7;");
+        self.writeln("    else if (strncmp(url, \"https://\", 8) == 0) { start = url + 8; *port = 443; }");
+        self.writeln("    const char* slash = strchr(start, '/');");
+        self.writeln("    const char* colon = strchr(start, ':');");
+        self.writeln("    if (colon && (!slash || colon < slash)) {");
+        self.writeln("        strncpy(host, start, colon - start);");
+        self.writeln("        host[colon - start] = '\\0';");
+        self.writeln("        *port = atoi(colon + 1);");
+        self.writeln("    } else if (slash) {");
+        self.writeln("        strncpy(host, start, slash - start);");
+        self.writeln("        host[slash - start] = '\\0';");
+        self.writeln("    } else {");
+        self.writeln("        strcpy(host, start);");
+        self.writeln("    }");
+        self.writeln("    if (slash) strcpy(path, slash);");
+        self.writeln("    return 0;");
+        self.writeln("}");
+        self.writeln("");
+        self.writeln("static LuxString lux_http_request(const char* method, LuxString url, LuxString body) {");
+        self.writeln("    char host[256], path[1024];");
+        self.writeln("    int port;");
+        self.writeln("    lux_http_parse_url(url, host, &port, path);");
+        self.writeln("");
+        self.writeln("    struct hostent* server = gethostbyname(host);");
+        self.writeln("    if (!server) return strdup(\"Error: Could not resolve host\");");
+        self.writeln("");
+        self.writeln("    int sockfd = socket(AF_INET, SOCK_STREAM, 0);");
+        self.writeln("    if (sockfd < 0) return strdup(\"Error: Could not create socket\");");
+        self.writeln("");
+        self.writeln("    struct sockaddr_in serv_addr;");
+        self.writeln("    memset(&serv_addr, 0, sizeof(serv_addr));");
+        self.writeln("    serv_addr.sin_family = AF_INET;");
+        self.writeln("    memcpy(&serv_addr.sin_addr.s_addr, server->h_addr, server->h_length);");
+        self.writeln("    serv_addr.sin_port = htons(port);");
+        self.writeln("");
+        self.writeln("    if (connect(sockfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr)) < 0) {");
+        self.writeln("        close(sockfd);");
+        self.writeln("        return strdup(\"Error: Connection failed\");");
+        self.writeln("    }");
+        self.writeln("");
+        self.writeln("    char request[4096];");
+        self.writeln("    if (body && strlen(body) > 0) {");
+        self.writeln("        snprintf(request, sizeof(request),");
+        self.writeln("            \"%s %s HTTP/1.1\\r\\n\"");
+        self.writeln("            \"Host: %s\\r\\n\"");
+        self.writeln("            \"Content-Type: application/x-www-form-urlencoded\\r\\n\"");
+        self.writeln("            \"Content-Length: %zu\\r\\n\"");
+        self.writeln("            \"Connection: close\\r\\n\\r\\n%s\",");
+        self.writeln("            method, path, host, strlen(body), body);");
+        self.writeln("    } else {");
+        self.writeln("        snprintf(request, sizeof(request),");
+        self.writeln("            \"%s %s HTTP/1.1\\r\\n\"");
+        self.writeln("            \"Host: %s\\r\\n\"");
+        self.writeln("            \"Connection: close\\r\\n\\r\\n\",");
+        self.writeln("            method, path, host);");
+        self.writeln("    }");
+        self.writeln("");
+        self.writeln("    send(sockfd, request, strlen(request), 0);");
+        self.writeln("");
+        self.writeln("    char* response = malloc(65536);");
+        self.writeln("    size_t total = 0;");
+        self.writeln("    ssize_t n;");
+        self.writeln("    while ((n = recv(sockfd, response + total, 65536 - total - 1, 0)) > 0) {");
+        self.writeln("        total += n;");
+        self.writeln("        if (total >= 65535) break;");
+        self.writeln("    }");
+        self.writeln("    response[total] = '\\0';");
+        self.writeln("    close(sockfd);");
+        self.writeln("");
+        self.writeln("    // Find body (after \\r\\n\\r\\n)");
+        self.writeln("    char* body_start = strstr(response, \"\\r\\n\\r\\n\");");
+        self.writeln("    if (body_start) {");
+        self.writeln("        body_start += 4;");
+        self.writeln("        char* result = strdup(body_start);");
+        self.writeln("        free(response);");
+        self.writeln("        return result;");
+        self.writeln("    }");
+        self.writeln("    return response;");
+        self.writeln("}");
+        self.writeln("");
+        self.writeln("static LuxString lux_http_get(LuxString url) {");
+        self.writeln("    return lux_http_request(\"GET\", url, NULL);");
+        self.writeln("}");
+        self.writeln("");
+        self.writeln("static LuxString lux_http_post(LuxString url, LuxString body) {");
+        self.writeln("    return lux_http_request(\"POST\", url, body);");
+        self.writeln("}");
+        self.writeln("");
+        self.writeln("static LuxString lux_http_put(LuxString url, LuxString body) {");
+        self.writeln("    return lux_http_request(\"PUT\", url, body);");
+        self.writeln("}");
+        self.writeln("");
+        self.writeln("static LuxString lux_http_delete(LuxString url) {");
+        self.writeln("    return lux_http_request(\"DELETE\", url, NULL);");
+        self.writeln("}");
+        self.writeln("");
+        self.writeln("static LuxString default_http_get(void* env, LuxString url) {");
+        self.writeln("    (void)env;");
+        self.writeln("    return lux_http_get(url);");
+        self.writeln("}");
+        self.writeln("");
+        self.writeln("static LuxString default_http_post(void* env, LuxString url, LuxString body) {");
+        self.writeln("    (void)env;");
+        self.writeln("    return lux_http_post(url, body);");
+        self.writeln("}");
+        self.writeln("");
+        self.writeln("static LuxString default_http_put(void* env, LuxString url, LuxString body) {");
+        self.writeln("    (void)env;");
+        self.writeln("    return lux_http_put(url, body);");
+        self.writeln("}");
+        self.writeln("");
+        self.writeln("static LuxString default_http_delete(void* env, LuxString url) {");
+        self.writeln("    (void)env;");
+        self.writeln("    return lux_http_delete(url);");
+        self.writeln("}");
+        self.writeln("");
+        self.writeln("static LuxHttpHandler default_http_handler = {");
+        self.writeln("    .get = default_http_get,");
+        self.writeln("    .post = default_http_post,");
+        self.writeln("    .put = default_http_put,");
+        self.writeln("    .delete_req = default_http_delete,");
+        self.writeln("    .env = NULL");
+        self.writeln("};");
+        self.writeln("");
         self.writeln("// Default evidence with built-in handlers");
         self.writeln("static LuxEvidence default_evidence = {");
         self.writeln("    .console = &default_console_handler,");
@@ -679,7 +825,8 @@ impl CBackend {
         self.writeln("    .reader = NULL,");
         self.writeln("    .random = &default_random_handler,");
         self.writeln("    .time = &default_time_handler,");
-        self.writeln("    .file = &default_file_handler");
+        self.writeln("    .file = &default_file_handler,");
+        self.writeln("    .http = &default_http_handler");
         self.writeln("};");
         self.writeln("");
         self.writeln("// === List Types ===");
@@ -1409,6 +1556,47 @@ impl CBackend {
                     }
                 }
 
+                // Built-in Http effect
+                if effect.name == "Http" {
+                    match operation.name.as_str() {
+                        "get" => {
+                            let url = self.emit_expr(&args[0])?;
+                            if self.has_evidence {
+                                return Ok(format!("ev->http->get(ev->http->env, {})", url));
+                            } else {
+                                return Ok(format!("lux_http_get({})", url));
+                            }
+                        }
+                        "post" => {
+                            let url = self.emit_expr(&args[0])?;
+                            let body = self.emit_expr(&args[1])?;
+                            if self.has_evidence {
+                                return Ok(format!("ev->http->post(ev->http->env, {}, {})", url, body));
+                            } else {
+                                return Ok(format!("lux_http_post({}, {})", url, body));
+                            }
+                        }
+                        "put" => {
+                            let url = self.emit_expr(&args[0])?;
+                            let body = self.emit_expr(&args[1])?;
+                            if self.has_evidence {
+                                return Ok(format!("ev->http->put(ev->http->env, {}, {})", url, body));
+                            } else {
+                                return Ok(format!("lux_http_put({}, {})", url, body));
+                            }
+                        }
+                        "delete" => {
+                            let url = self.emit_expr(&args[0])?;
+                            if self.has_evidence {
+                                return Ok(format!("ev->http->delete_req(ev->http->env, {})", url));
+                            } else {
+                                return Ok(format!("lux_http_delete({})", url));
+                            }
+                        }
+                        _ => {}
+                    }
+                }
+
                 // For other effects, emit generic evidence-passing call
                 let arg_strs: Result<Vec<_>, _> = args.iter().map(|a| self.emit_expr(a)).collect();
                 if self.has_evidence {
@@ -1915,6 +2103,11 @@ impl CBackend {
                         "exists" | "isDir" => Some("LuxBool".to_string()),
                         _ => None,
                     }
+                } else if effect.name == "Http" {
+                    match operation.name.as_str() {
+                        "get" | "post" | "put" | "delete" => Some("LuxString".to_string()),
+                        _ => None,
+                    }
                 } else if effect.name == "Console" {
                     match operation.name.as_str() {
                         "print" => Some("void".to_string()),