package httpapi

import (
	"bytes"
	"encoding/json"
	"fmt"
	"net/http"
	"net/http/httptest"
	"strings"
	"sync"
	"testing"
	"time"
)

func TestConcurrentUploadsRemainConsistentAndReadable(t *testing.T) {
	t.Parallel()

	handler := newTestHandler(t, testServerOptions{
		maxUploadBytes:  1024 * 1024,
		defaultTTL:      time.Hour,
		rateLimitEnable: false,
	})

	const uploads = 80

	type createdScratch struct {
		id   string
		body string
	}

	resultsCh := make(chan createdScratch, uploads)
	errCh := make(chan error, uploads)
	var wg sync.WaitGroup

	for i := 0; i < uploads; i++ {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()

			body := fmt.Sprintf("parallel-upload-%03d-%s", i, strings.Repeat("x", i%17))
			createReq := httptest.NewRequest(http.MethodPost, "/api/scratch", bytes.NewBufferString(body))
			createReq.Header.Set("Content-Type", "text/plain; charset=utf-8")
			createReq.RemoteAddr = fmt.Sprintf("127.0.0.1:%d", 8200+i)
			createRec := httptest.NewRecorder()
			handler.ServeHTTP(createRec, createReq)
			if createRec.Code != http.StatusCreated {
				errCh <- fmt.Errorf("create status = %d, want %d", createRec.Code, http.StatusCreated)
				return
			}

			var payload map[string]any
			if err := json.Unmarshal(createRec.Body.Bytes(), &payload); err != nil {
				errCh <- fmt.Errorf("decode create payload error: %w", err)
				return
			}
			id, _ := payload["id"].(string)
			if id == "" {
				errCh <- fmt.Errorf("create payload missing id")
				return
			}

			metaReq := httptest.NewRequest(http.MethodGet, "/api/scratch/"+id, nil)
			metaRec := httptest.NewRecorder()
			handler.ServeHTTP(metaRec, metaReq)
			if metaRec.Code != http.StatusOK {
				errCh <- fmt.Errorf("metadata status = %d, want %d", metaRec.Code, http.StatusOK)
				return
			}

			rawReq := httptest.NewRequest(http.MethodGet, "/api/raw/"+id, nil)
			rawRec := httptest.NewRecorder()
			handler.ServeHTTP(rawRec, rawReq)
			if rawRec.Code != http.StatusOK {
				errCh <- fmt.Errorf("raw status = %d, want %d", rawRec.Code, http.StatusOK)
				return
			}
			if got := rawRec.Body.String(); got != body {
				errCh <- fmt.Errorf("raw body mismatch = %q, want %q", got, body)
				return
			}

			resultsCh <- createdScratch{id: id, body: body}
		}(i)
	}

	wg.Wait()
	close(resultsCh)
	close(errCh)
	for err := range errCh {
		t.Error(err)
	}

	seen := make(map[string]struct{}, uploads)
	for result := range resultsCh {
		if _, exists := seen[result.id]; exists {
			t.Errorf("duplicate scratch id generated: %s", result.id)
			continue
		}
		seen[result.id] = struct{}{}
	}
	if len(seen) != uploads {
		t.Fatalf("unique IDs = %d, want %d", len(seen), uploads)
	}
}

func TestParallelClientsCanReadSameScratchAcrossAllReadRoutes(t *testing.T) {
	t.Parallel()

	handler := newTestHandler(t, testServerOptions{
		maxUploadBytes:  1024,
		defaultTTL:      time.Hour,
		rateLimitEnable: false,
	})

	const body = "parallel readers"
	createReq := httptest.NewRequest(http.MethodPost, "/api/scratch", bytes.NewBufferString(body))
	createReq.Header.Set("Content-Type", "text/plain; charset=utf-8")
	createReq.RemoteAddr = "127.0.0.1:6010"
	createRec := httptest.NewRecorder()
	handler.ServeHTTP(createRec, createReq)
	if createRec.Code != http.StatusCreated {
		t.Fatalf("create status = %d, want %d", createRec.Code, http.StatusCreated)
	}

	var payload map[string]any
	if err := json.Unmarshal(createRec.Body.Bytes(), &payload); err != nil {
		t.Fatalf("decode create payload error = %v", err)
	}
	id, _ := payload["id"].(string)
	if id == "" {
		t.Fatalf("create payload missing id")
	}

	paths := []string{
		"/api/raw/" + id,
		"/s/" + id,
		"/api/scratch/" + id,
	}
	const requests = 120

	errCh := make(chan error, requests)
	var wg sync.WaitGroup
	for i := 0; i < requests; i++ {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()
			path := paths[i%len(paths)]
			req := httptest.NewRequest(http.MethodGet, path, nil)
			req.RemoteAddr = fmt.Sprintf("127.0.0.1:%d", 6100+i)
			rec := httptest.NewRecorder()
			handler.ServeHTTP(rec, req)

			if rec.Code != http.StatusOK {
				errCh <- fmt.Errorf("path %s status = %d, want %d", path, rec.Code, http.StatusOK)
				return
			}

			switch {
			case strings.HasPrefix(path, "/api/raw/"):
				if got := rec.Body.String(); got != body {
					errCh <- fmt.Errorf("raw body = %q, want %q", got, body)
				}
			case strings.HasPrefix(path, "/s/"):
				if !strings.Contains(rec.Body.String(), `id="app"`) {
					errCh <- fmt.Errorf("view body missing SPA marker")
				}
			case strings.HasPrefix(path, "/api/scratch/"):
				var gotPayload map[string]any
				if err := json.Unmarshal(rec.Body.Bytes(), &gotPayload); err != nil {
					errCh <- fmt.Errorf("metadata decode error: %w", err)
					return
				}
				if gotID, _ := gotPayload["id"].(string); gotID != id {
					errCh <- fmt.Errorf("metadata id = %q, want %q", gotID, id)
				}
			}
		}(i)
	}
	wg.Wait()
	close(errCh)
	for err := range errCh {
		t.Error(err)
	}
}

func TestParallelClientsExpiredScratchReadsReturnGone(t *testing.T) {
	t.Parallel()

	handler := newTestHandler(t, testServerOptions{
		maxUploadBytes:  1024,
		defaultTTL:      80 * time.Millisecond,
		rateLimitEnable: false,
	})

	createReq := httptest.NewRequest(http.MethodPost, "/api/scratch", bytes.NewBufferString("expires soon"))
	createReq.Header.Set("Content-Type", "text/plain; charset=utf-8")
	createReq.RemoteAddr = "127.0.0.1:7010"
	createRec := httptest.NewRecorder()
	handler.ServeHTTP(createRec, createReq)
	if createRec.Code != http.StatusCreated {
		t.Fatalf("create status = %d, want %d", createRec.Code, http.StatusCreated)
	}

	var payload map[string]any
	if err := json.Unmarshal(createRec.Body.Bytes(), &payload); err != nil {
		t.Fatalf("decode create payload error = %v", err)
	}
	id, _ := payload["id"].(string)
	if id == "" {
		t.Fatalf("create payload missing id")
	}

	time.Sleep(130 * time.Millisecond)

	paths := []string{
		"/api/raw/" + id,
		"/s/" + id,
		"/api/scratch/" + id,
	}
	const requests = 90

	errCh := make(chan error, requests)
	var wg sync.WaitGroup
	for i := 0; i < requests; i++ {
		wg.Add(1)
		go func(i int) {
			defer wg.Done()
			path := paths[i%len(paths)]
			req := httptest.NewRequest(http.MethodGet, path, nil)
			req.RemoteAddr = fmt.Sprintf("127.0.0.1:%d", 7100+i)
			rec := httptest.NewRecorder()
			handler.ServeHTTP(rec, req)

			if rec.Code != http.StatusGone {
				errCh <- fmt.Errorf("expired path %s status = %d, want %d", path, rec.Code, http.StatusGone)
				return
			}

			if strings.HasPrefix(path, "/s/") && !strings.Contains(rec.Body.String(), `id="app"`) {
				errCh <- fmt.Errorf("expired view body missing SPA marker")
			}
		}(i)
	}
	wg.Wait()
	close(errCh)
	for err := range errCh {
		t.Error(err)
	}
}