package main

import (
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"testing"
	"time"

	"gcy_hpc_server/internal/testutil/testenv"
)

// taskAPIResponse decodes the unified API response envelope.
type taskAPIResponse struct {
	Success bool            `json:"success"`
	Data    json.RawMessage `json:"data,omitempty"`
	Error   string          `json:"error,omitempty"`
}

// taskCreateData is the data payload from a successful task creation.
type taskCreateData struct {
	ID int64 `json:"id"`
}

// taskListData is the data payload from listing tasks.
type taskListData struct {
	Items []taskListItem `json:"items"`
	Total int64          `json:"total"`
}

type taskListItem struct {
	ID         int64  `json:"id"`
	TaskName   string `json:"task_name"`
	AppID      int64  `json:"app_id"`
	Status     string `json:"status"`
	SlurmJobID *int32 `json:"slurm_job_id"`
}

// taskSendReq sends an HTTP request via the test env and returns the response.
func taskSendReq(t *testing.T, env *testenv.TestEnv, method, path string, body string) *http.Response {
	t.Helper()
	var r io.Reader
	if body != "" {
		r = strings.NewReader(body)
	}
	resp := env.DoRequest(method, path, r)
	return resp
}

// taskParseResp decodes the response body into a taskAPIResponse.
func taskParseResp(t *testing.T, resp *http.Response) taskAPIResponse {
	t.Helper()
	b, err := io.ReadAll(resp.Body)
	resp.Body.Close()
	if err != nil {
		t.Fatalf("read response body: %v", err)
	}
	var result taskAPIResponse
	if err := json.Unmarshal(b, &result); err != nil {
		t.Fatalf("unmarshal response: %v (body: %s)", err, string(b))
	}
	return result
}

// taskCreateViaAPI creates a task via the HTTP API and returns the task ID.
func taskCreateViaAPI(t *testing.T, env *testenv.TestEnv, appID int64, taskName string) int64 {
	t.Helper()
	body := fmt.Sprintf(`{"app_id":%d,"task_name":"%s","values":{},"file_ids":[]}`, appID, taskName)
	resp := taskSendReq(t, env, http.MethodPost, "/api/v1/tasks", body)
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusCreated {
		b, _ := io.ReadAll(resp.Body)
		t.Fatalf("expected 201, got %d: %s", resp.StatusCode, string(b))
	}

	parsed := taskParseResp(t, resp)
	if !parsed.Success {
		t.Fatalf("expected success=true, got error: %s", parsed.Error)
	}

	var data taskCreateData
	if err := json.Unmarshal(parsed.Data, &data); err != nil {
		t.Fatalf("unmarshal create data: %v", err)
	}
	if data.ID == 0 {
		t.Fatal("expected non-zero task ID")
	}
	return data.ID
}

// ---------- Tests ----------

func TestIntegration_Task_Create(t *testing.T) {
	env := testenv.NewTestEnv(t)

	// Create application
	appID, err := env.CreateApp("task-create-app", "#!/bin/bash\necho hello", nil)
	if err != nil {
		t.Fatalf("create app: %v", err)
	}

	// Create task via API
	taskID := taskCreateViaAPI(t, env, appID, "test-task-create")

	// Verify the task ID is positive
	if taskID <= 0 {
		t.Fatalf("expected positive task ID, got %d", taskID)
	}

	// Wait briefly for async processing, then verify task exists in DB via list
	time.Sleep(200 * time.Millisecond)

	resp := taskSendReq(t, env, http.MethodGet, "/api/v1/tasks", "")
	defer resp.Body.Close()
	parsed := taskParseResp(t, resp)

	var listData taskListData
	if err := json.Unmarshal(parsed.Data, &listData); err != nil {
		t.Fatalf("unmarshal list data: %v", err)
	}

	found := false
	for _, item := range listData.Items {
		if item.ID == taskID {
			found = true
			if item.TaskName != "test-task-create" {
				t.Errorf("expected task_name=test-task-create, got %s", item.TaskName)
			}
			if item.AppID != appID {
				t.Errorf("expected app_id=%d, got %d", appID, item.AppID)
			}
			break
		}
	}
	if !found {
		t.Fatalf("task %d not found in list", taskID)
	}
}

func TestIntegration_Task_List(t *testing.T) {
	env := testenv.NewTestEnv(t)

	// Create application
	appID, err := env.CreateApp("task-list-app", "#!/bin/bash\necho hello", nil)
	if err != nil {
		t.Fatalf("create app: %v", err)
	}

	// Create 3 tasks
	taskCreateViaAPI(t, env, appID, "list-task-1")
	taskCreateViaAPI(t, env, appID, "list-task-2")
	taskCreateViaAPI(t, env, appID, "list-task-3")

	// Allow async processing
	time.Sleep(200 * time.Millisecond)

	// List tasks
	resp := taskSendReq(t, env, http.MethodGet, "/api/v1/tasks", "")
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		b, _ := io.ReadAll(resp.Body)
		t.Fatalf("expected 200, got %d: %s", resp.StatusCode, string(b))
	}

	parsed := taskParseResp(t, resp)
	if !parsed.Success {
		t.Fatalf("expected success, got error: %s", parsed.Error)
	}

	var listData taskListData
	if err := json.Unmarshal(parsed.Data, &listData); err != nil {
		t.Fatalf("unmarshal list data: %v", err)
	}

	if listData.Total < 3 {
		t.Fatalf("expected at least 3 tasks, got %d", listData.Total)
	}

	// Verify each created task has required fields
	for _, item := range listData.Items {
		if item.ID == 0 {
			t.Error("expected non-zero ID")
		}
		if item.Status == "" {
			t.Error("expected non-empty status")
		}
		if item.AppID == 0 {
			t.Error("expected non-zero app_id")
		}
	}
}

func TestIntegration_Task_PollerLifecycle(t *testing.T) {
	env := testenv.NewTestEnv(t)

	// 1. Create application
	appID, err := env.CreateApp("poller-lifecycle-app", "#!/bin/bash\necho hello", nil)
	if err != nil {
		t.Fatalf("create app: %v", err)
	}

	// 2. Submit task via API
	taskID := taskCreateViaAPI(t, env, appID, "poller-lifecycle-task")

	// 3. Wait for queued — TaskProcessor submits to MockSlurm asynchronously.
	//    Intermediate states (submitted→preparing→downloading→ready→queued) are
	//    non-deterministic; only assert the final "queued" state.
	if err := env.WaitForTaskStatus(taskID, "queued", 5*time.Second); err != nil {
		t.Fatalf("wait for queued: %v", err)
	}

	// 4. Get slurm job ID from DB (not returned by API)
	slurmJobID, err := env.GetTaskSlurmJobID(taskID)
	if err != nil {
		t.Fatalf("get slurm job id: %v", err)
	}

	// 5. Transition: queued → running
	//    ORDER IS CRITICAL: SetJobState BEFORE MakeTaskStale
	env.MockSlurm.SetJobState(slurmJobID, "RUNNING")
	if err := env.MakeTaskStale(taskID); err != nil {
		t.Fatalf("make task stale (running): %v", err)
	}
	if err := env.WaitForTaskStatus(taskID, "running", 5*time.Second); err != nil {
		t.Fatalf("wait for running: %v", err)
	}

	// 6. Transition: running → completed
	//    ORDER IS CRITICAL: SetJobState BEFORE MakeTaskStale
	env.MockSlurm.SetJobState(slurmJobID, "COMPLETED")
	if err := env.MakeTaskStale(taskID); err != nil {
		t.Fatalf("make task stale (completed): %v", err)
	}
	if err := env.WaitForTaskStatus(taskID, "completed", 5*time.Second); err != nil {
		t.Fatalf("wait for completed: %v", err)
	}
}

func TestIntegration_Task_Validation(t *testing.T) {
	env := testenv.NewTestEnv(t)

	// Missing required app_id
	resp := taskSendReq(t, env, http.MethodPost, "/api/v1/tasks", `{"task_name":"no-app-id"}`)
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusBadRequest {
		t.Fatalf("expected 400 for missing app_id, got %d", resp.StatusCode)
	}

	parsed := taskParseResp(t, resp)
	if parsed.Success {
		t.Fatal("expected success=false for validation error")
	}
	if parsed.Error == "" {
		t.Error("expected non-empty error message")
	}
}