package openai

import (
	"bytes"
	"context"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"strconv"
	"strings"
	"time"

	"github.com/QuantumNous/new-api/common"
	"github.com/QuantumNous/new-api/logger"
	relaycommon "github.com/QuantumNous/new-api/relay/common"
	"github.com/QuantumNous/new-api/service"

	"github.com/gin-gonic/gin"
)

const (
	maxImageTaskResponseBytes    int64 = 64 * 1024 * 1024
	defaultImageTaskPollTimeout        = 120 * time.Second
	defaultImageTaskPollDelay          = 2 * time.Second
	minImageTaskPollDelay              = 250 * time.Millisecond
	maxImageTaskPollDelay              = 5 * time.Second
	maxImageTaskPollErrors             = 3
)

type openAIImageTaskEnvelope struct {
	Object      string `json:"object"`
	Status      string `json:"status"`
	TaskID      string `json:"task_id"`
	ID          string `json:"id"`
	PollURL     string `json:"poll_url"`
	ResultURL   string `json:"result_url"`
	PollAfterMS int64  `json:"poll_after_ms"`
	Error       string `json:"error"`
	ErrorCode   string `json:"error_code"`
}

type imageTaskPollStats struct {
	TaskID   string
	Attempts int
	Duration time.Duration
}

type imageTaskWaitFunc func(context.Context, time.Duration) error

func resolveOpenAIImageTask(c *gin.Context, info *relaycommon.RelayInfo, response *http.Response) (*http.Response, error) {
	if !common.GetEnvOrDefaultBool("CODEX_IMAGE_TASK_POLL", false) || response == nil || response.StatusCode != http.StatusAccepted {
		return response, nil
	}
	if info == nil {
		return nil, fmt.Errorf("image task relay info is missing")
	}

	client, err := service.GetHttpClientWithProxy(info.ChannelSetting.Proxy)
	if err != nil {
		return nil, fmt.Errorf("create image task poll client: %w", err)
	}

	timeoutSeconds := common.GetEnvOrDefault("CODEX_IMAGE_TASK_POLL_TIMEOUT_SECONDS", int(defaultImageTaskPollTimeout/time.Second))
	if timeoutSeconds < 1 {
		timeoutSeconds = int(defaultImageTaskPollTimeout / time.Second)
	}
	if timeoutSeconds > 600 {
		timeoutSeconds = 600
	}

	startedAt := time.Now()
	resolved, stats, err := pollOpenAIImageTask(
		c.Request.Context(),
		response,
		client,
		time.Duration(timeoutSeconds)*time.Second,
		waitForOpenAIImageTask,
	)
	stats.Duration = time.Since(startedAt)
	if err != nil {
		return nil, err
	}
	if stats.Attempts > 0 {
		logger.LogInfo(c, fmt.Sprintf(
			"image task compatibility completed task_id=%s attempts=%d total_ms=%.3f",
			maskImageTaskID(stats.TaskID),
			stats.Attempts,
			float64(stats.Duration.Microseconds())/1000,
		))
		resolved.Header.Set("X-New-API-Image-Task-Compat", "polled")
	}
	return resolved, nil
}

func pollOpenAIImageTask(
	ctx context.Context,
	initial *http.Response,
	client *http.Client,
	timeout time.Duration,
	wait imageTaskWaitFunc,
) (*http.Response, imageTaskPollStats, error) {
	var stats imageTaskPollStats
	if initial == nil || initial.Body == nil {
		return nil, stats, fmt.Errorf("image task response is empty")
	}
	if initial.StatusCode != http.StatusAccepted {
		return initial, stats, nil
	}

	initialBody, err := readImageTaskResponseBody(initial)
	if err != nil {
		return nil, stats, err
	}
	initial.Body = io.NopCloser(bytes.NewReader(initialBody))
	initial.ContentLength = int64(len(initialBody))

	task, isTask, err := parseOpenAIImageTask(initialBody)
	if err != nil {
		return nil, stats, err
	}
	if !isTask {
		return initial, stats, nil
	}

	stats.TaskID = firstNonEmpty(task.TaskID, task.ID)
	baseURL, err := imageTaskBaseURL(initial)
	if err != nil {
		return nil, stats, err
	}
	pollClient := *client
	pollClient.CheckRedirect = func(request *http.Request, via []*http.Request) error {
		if len(via) >= 10 {
			return fmt.Errorf("image task polling stopped after 10 redirects")
		}
		if request == nil || request.URL == nil ||
			!strings.EqualFold(baseURL.Scheme, request.URL.Scheme) ||
			!strings.EqualFold(baseURL.Host, request.URL.Host) {
			return fmt.Errorf("image task redirect must use the original upstream origin")
		}
		return nil
	}
	client = &pollClient
	pollURL, err := resolveImageTaskPollURL(baseURL, firstNonEmpty(task.PollURL, task.ResultURL))
	if err != nil {
		return nil, stats, err
	}

	deadline := time.Now().Add(timeout)
	consecutiveErrors := 0
	for {
		if remaining := time.Until(deadline); remaining <= 0 {
			return nil, stats, fmt.Errorf("image task polling timed out after %s (task_id=%s)", timeout, maskImageTaskID(stats.TaskID))
		}

		delay := imageTaskPollDelay(task.PollAfterMS)
		if remaining := time.Until(deadline); delay > remaining {
			delay = remaining
		}
		if err := wait(ctx, delay); err != nil {
			return nil, stats, fmt.Errorf("image task polling stopped: %w", err)
		}

		request, err := http.NewRequestWithContext(ctx, http.MethodGet, pollURL.String(), nil)
		if err != nil {
			return nil, stats, fmt.Errorf("create image task poll request: %w", err)
		}
		copyImageTaskAuthHeaders(request.Header, initial.Request)
		request.Header.Set("Accept", "application/json")

		pollResponse, err := client.Do(request)
		stats.Attempts++
		if err != nil {
			consecutiveErrors++
			if consecutiveErrors >= maxImageTaskPollErrors {
				return nil, stats, fmt.Errorf("poll image task after %d consecutive errors: %w", consecutiveErrors, err)
			}
			continue
		}

		pollBody, readErr := readImageTaskResponseBody(pollResponse)
		if readErr != nil {
			return nil, stats, readErr
		}
		if pollResponse.StatusCode >= http.StatusInternalServerError {
			consecutiveErrors++
			if consecutiveErrors >= maxImageTaskPollErrors {
				return nil, stats, fmt.Errorf("poll image task returned HTTP %d after %d attempts", pollResponse.StatusCode, consecutiveErrors)
			}
			continue
		}
		consecutiveErrors = 0
		if pollResponse.StatusCode < http.StatusOK || pollResponse.StatusCode >= http.StatusMultipleChoices {
			return nil, stats, fmt.Errorf("poll image task returned HTTP %d", pollResponse.StatusCode)
		}

		if isFinalOpenAIImageResponse(pollBody) {
			pollResponse.StatusCode = http.StatusOK
			pollResponse.Status = fmt.Sprintf("%d %s", http.StatusOK, http.StatusText(http.StatusOK))
			pollResponse.Body = io.NopCloser(bytes.NewReader(pollBody))
			pollResponse.ContentLength = int64(len(pollBody))
			pollResponse.Header.Del("Content-Encoding")
			pollResponse.Header.Set("Content-Length", strconv.FormatInt(int64(len(pollBody)), 10))
			return pollResponse, stats, nil
		}

		nextTask, nextIsTask, err := parseOpenAIImageTask(pollBody)
		if err != nil {
			return nil, stats, err
		}
		if !nextIsTask {
			return nil, stats, fmt.Errorf("image task poll response is neither a task nor a final image response")
		}
		task = nextTask
		if nextID := firstNonEmpty(task.TaskID, task.ID); nextID != "" {
			stats.TaskID = nextID
		}

		switch strings.ToLower(strings.TrimSpace(task.Status)) {
		case "failed", "cancelled", "canceled", "expired":
			message := firstNonEmpty(task.Error, task.ErrorCode, task.Status)
			return nil, stats, fmt.Errorf("image task %s: %s", maskImageTaskID(stats.TaskID), message)
		case "completed", "succeeded", "success":
			return nil, stats, fmt.Errorf("image task %s completed without image data", maskImageTaskID(stats.TaskID))
		}

		if nextRawURL := firstNonEmpty(task.PollURL, task.ResultURL); nextRawURL != "" {
			pollURL, err = resolveImageTaskPollURL(baseURL, nextRawURL)
			if err != nil {
				return nil, stats, err
			}
		}
	}
}

func parseOpenAIImageTask(body []byte) (openAIImageTaskEnvelope, bool, error) {
	var task openAIImageTaskEnvelope
	if err := common.Unmarshal(body, &task); err != nil {
		return task, false, fmt.Errorf("decode image task response: %w", err)
	}
	if !strings.EqualFold(strings.TrimSpace(task.Object), "image.task") {
		return task, false, nil
	}
	if firstNonEmpty(task.PollURL, task.ResultURL) == "" {
		return task, false, fmt.Errorf("image task response is missing poll_url")
	}
	return task, true, nil
}

func isFinalOpenAIImageResponse(body []byte) bool {
	var payload map[string]json.RawMessage
	if err := common.Unmarshal(body, &payload); err != nil {
		return false
	}
	if _, ok := payload["created"]; !ok {
		return false
	}
	var images []json.RawMessage
	if err := common.Unmarshal(payload["data"], &images); err != nil {
		return false
	}
	return len(images) > 0
}

func imageTaskBaseURL(response *http.Response) (*url.URL, error) {
	if response.Request == nil || response.Request.URL == nil {
		return nil, fmt.Errorf("image task response is missing its upstream request URL")
	}
	base := response.Request.URL
	if base.Scheme != "http" && base.Scheme != "https" {
		return nil, fmt.Errorf("unsupported image task upstream scheme: %s", base.Scheme)
	}
	if base.User != nil || base.Hostname() == "" {
		return nil, fmt.Errorf("invalid image task upstream URL")
	}
	return base, nil
}

func resolveImageTaskPollURL(baseURL *url.URL, rawURL string) (*url.URL, error) {
	if baseURL == nil {
		return nil, fmt.Errorf("image task upstream URL is missing")
	}
	reference, err := url.Parse(strings.TrimSpace(rawURL))
	if err != nil {
		return nil, fmt.Errorf("parse image task poll URL: %w", err)
	}
	resolved := baseURL.ResolveReference(reference)
	if resolved.Scheme != "http" && resolved.Scheme != "https" {
		return nil, fmt.Errorf("unsupported image task poll scheme: %s", resolved.Scheme)
	}
	if resolved.User != nil || resolved.Hostname() == "" {
		return nil, fmt.Errorf("invalid image task poll URL")
	}
	if !strings.EqualFold(baseURL.Scheme, resolved.Scheme) || !strings.EqualFold(baseURL.Host, resolved.Host) {
		return nil, fmt.Errorf("image task poll URL must use the original upstream origin")
	}
	return resolved, nil
}

func copyImageTaskAuthHeaders(destination http.Header, source *http.Request) {
	if source == nil {
		return
	}
	for _, name := range []string{"Authorization", "Api-Key", "X-Api-Key"} {
		for _, value := range source.Header.Values(name) {
			destination.Add(name, value)
		}
	}
}

func readImageTaskResponseBody(response *http.Response) ([]byte, error) {
	if response == nil || response.Body == nil {
		return nil, fmt.Errorf("image task response is empty")
	}
	defer response.Body.Close()
	if response.ContentLength > maxImageTaskResponseBytes {
		return nil, fmt.Errorf("image task response exceeds %d bytes", maxImageTaskResponseBytes)
	}
	body, err := io.ReadAll(io.LimitReader(response.Body, maxImageTaskResponseBytes+1))
	if err != nil {
		return nil, fmt.Errorf("read image task response: %w", err)
	}
	if int64(len(body)) > maxImageTaskResponseBytes {
		return nil, fmt.Errorf("image task response exceeds %d bytes", maxImageTaskResponseBytes)
	}
	return body, nil
}

func imageTaskPollDelay(milliseconds int64) time.Duration {
	if milliseconds <= 0 {
		return defaultImageTaskPollDelay
	}
	delay := time.Duration(milliseconds) * time.Millisecond
	if delay < minImageTaskPollDelay {
		return minImageTaskPollDelay
	}
	if delay > maxImageTaskPollDelay {
		return maxImageTaskPollDelay
	}
	return delay
}

func waitForOpenAIImageTask(ctx context.Context, delay time.Duration) error {
	timer := time.NewTimer(delay)
	defer timer.Stop()
	select {
	case <-ctx.Done():
		return ctx.Err()
	case <-timer.C:
		return nil
	}
}

func firstNonEmpty(values ...string) string {
	for _, value := range values {
		if trimmed := strings.TrimSpace(value); trimmed != "" {
			return trimmed
		}
	}
	return ""
}

func maskImageTaskID(taskID string) string {
	taskID = strings.TrimSpace(taskID)
	if len(taskID) <= 12 {
		return taskID
	}
	return taskID[:8] + "..." + taskID[len(taskID)-4:]
}