feat(core): support COOKIE parameter location

core/src/main/kotlin/com/avsystem/justworks/core/gen/Names.kt

@@ -17,6 +17,7 @@ val SET_BODY_FUN = MemberName("io.ktor.client.request", "setBody")
 val CONTENT_TYPE_FUN = MemberName("io.ktor.http", "contentType")
 val CONTENT_TYPE_APPLICATION = ClassName("io.ktor.http", "ContentType", "Application")
 val HEADERS_FUN = MemberName("io.ktor.client.request", "headers")
+val COOKIE_FUN = MemberName("io.ktor.client.request", "cookie")
 
 val GET_FUN = MemberName("io.ktor.client.request", "get")
 val POST_FUN = MemberName("io.ktor.client.request", "post")

core/src/main/kotlin/com/avsystem/justworks/core/gen/client/BodyGenerator.kt

@@ -6,6 +6,7 @@ import com.avsystem.justworks.core.gen.BODY
 import com.avsystem.justworks.core.gen.CLIENT
 import com.avsystem.justworks.core.gen.CONTENT_TYPE_APPLICATION
 import com.avsystem.justworks.core.gen.CONTENT_TYPE_FUN
+import com.avsystem.justworks.core.gen.COOKIE_FUN
 import com.avsystem.justworks.core.gen.DELETE_FUN
 import com.avsystem.justworks.core.gen.ENCODE_PARAM_FUN
 import com.avsystem.justworks.core.gen.FORM_DATA_FUN
@@ -197,6 +198,7 @@ internal object BodyGenerator {
     private fun CodeBlock.Builder.addCommonRequestParts(params: Map<ParameterLocation, List<Parameter>>) {
         addStatement("${APPLY_AUTH}()")
         addHeaderParams(params)
+        addCookieParams(params)
         addQueryParams(params)
     }
 
@@ -233,6 +235,18 @@ internal object BodyGenerator {
         }
     }
 
+    private fun CodeBlock.Builder.addCookieParams(params: Map<ParameterLocation, List<Parameter>>) {
+        val cookieParams = params[ParameterLocation.COOKIE]
+        if (!cookieParams.isNullOrEmpty()) {
+            for (param in cookieParams) {
+                val paramName = param.name.toCamelCase()
+                optionalGuard(param.required, paramName) {
+                    addStatement("%M(%S, %M(%L))", COOKIE_FUN, param.name, ENCODE_PARAM_FUN, paramName)
+                }
+            }
+        }
+    }
+
     private fun CodeBlock.Builder.addQueryParams(params: Map<ParameterLocation, List<Parameter>>) {
         val queryParams = params[ParameterLocation.QUERY]
         if (!queryParams.isNullOrEmpty()) {

core/src/main/kotlin/com/avsystem/justworks/core/gen/client/ClientGenerator.kt

@@ -245,7 +245,11 @@ internal object ClientGenerator {
             buildNullableParameter(param.schema, param.name, param.required)
         }
 
-        funBuilder.addParameters(pathParams + queryParams + headerParams)
+        val cookieParams = params[ParameterLocation.COOKIE].orEmpty().map { param ->
+            buildNullableParameter(param.schema, param.name, param.required)
+        }
+
+        funBuilder.addParameters(pathParams + queryParams + headerParams + cookieParams)
 
         if (endpoint.requestBody != null) {
             funBuilder.addParameters(buildBodyParams(endpoint.requestBody))

core/src/main/kotlin/com/avsystem/justworks/core/model/ApiSpec.kt

@@ -63,11 +63,11 @@ data class Parameter(
     val description: String?,
 )
 
-// todo: add cookie
 enum class ParameterLocation {
     PATH,
     QUERY,
-    HEADER
+    HEADER,
+    COOKIE
 }
 
 data class RequestBody(

core/src/test/kotlin/com/avsystem/justworks/core/gen/ClientGeneratorTest.kt

@@ -320,6 +320,72 @@ class ClientGeneratorTest {
         assertTrue(body.contains("append(\"X-Request-Id\""), "Expected header append inside headers block")
     }
 
+    // -- CLNT-09b: Cookie parameters --
+
+    @Test
+    fun `cookie parameters become function parameters`() {
+        val ep = endpoint(
+            operationId = "listPets",
+            parameters =
+                listOf(
+                    Parameter(
+                        "session",
+                        ParameterLocation.COOKIE,
+                        true,
+                        TypeRef.Primitive(PrimitiveType.STRING),
+                        null,
+                    ),
+                ),
+        )
+        val cls = clientClass(ep)
+        val funSpec = cls.funSpecs.first { it.name == "listPets" }
+        val param = funSpec.parameters.first { it.name == "session" }
+        assertEquals("kotlin.String", param.type.toString())
+    }
+
+    @Test
+    fun `required cookie parameters are emitted via cookie call`() {
+        val ep = endpoint(
+            operationId = "listPets",
+            parameters =
+                listOf(
+                    Parameter(
+                        "session",
+                        ParameterLocation.COOKIE,
+                        true,
+                        TypeRef.Primitive(PrimitiveType.STRING),
+                        null,
+                    ),
+                ),
+        )
+        val cls = clientClass(ep)
+        val funSpec = cls.funSpecs.first { it.name == "listPets" }
+        val body = funSpec.body.toString()
+        assertTrue(body.contains("cookie(\"session\""), "Expected cookie call in generated body")
+    }
+
+    @Test
+    fun `optional cookie parameters are null-guarded`() {
+        val ep = endpoint(
+            operationId = "listPets",
+            parameters =
+                listOf(
+                    Parameter(
+                        "session",
+                        ParameterLocation.COOKIE,
+                        false,
+                        TypeRef.Primitive(PrimitiveType.STRING),
+                        null,
+                    ),
+                ),
+        )
+        val cls = clientClass(ep)
+        val funSpec = cls.funSpecs.first { it.name == "listPets" }
+        val body = funSpec.body.toString()
+        assertTrue(body.contains("if (session != null)"), "Expected null guard for optional cookie")
+        assertTrue(body.contains("cookie(\"session\""), "Expected cookie call in generated body")
+    }
+
     // -- CLNT-10: Client constructor has baseUrl parameter --
 
     @Test

core/src/test/kotlin/com/avsystem/justworks/core/parser/SpecParserTest.kt

@@ -124,6 +124,41 @@ class SpecParserTest : SpecParserTestBase() {
         assertTrue(petIdParam.required, "Path parameter should be required")
     }
 
+    @Test
+    fun `parses cookie parameter location`() {
+        val spec = File.createTempFile("cookie-spec", ".yaml").apply { deleteOnExit() }
+        spec.writeText(
+            """
+            openapi: 3.0.0
+            info:
+              title: Cookie API
+              version: 1.0.0
+            paths:
+              /session:
+                get:
+                  operationId: getSession
+                  parameters:
+                    - name: session
+                      in: cookie
+                      required: true
+                      schema:
+                        type: string
+                  responses:
+                    '200':
+                      description: ok
+            """.trimIndent(),
+        )
+        val parsed = parseSpec(spec)
+        val getSession =
+            parsed.endpoints.find { it.operationId == "getSession" }
+                ?: fail("getSession endpoint not found")
+        val sessionParam =
+            getSession.parameters.find { it.name == "session" }
+                ?: fail("session parameter not found")
+        assertEquals(ParameterLocation.COOKIE, sessionParam.location)
+        assertTrue(sessionParam.required, "Cookie parameter should be required")
+    }
+
     @Test
     fun `parsed POST pets has requestBody referencing NewPet`() {
         val createPet =