package compat

import (
	"bytes"
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"log/slog"
	"net"
	"net/http"
	"strings"
	"time"

	thoughttypes "git.warky.dev/wdevs/amcs/internal/types"
)

const metadataSystemPrompt = `You extract structured metadata from short notes.
Return only valid JSON matching this schema:
{
  "people": ["string"],
  "action_items": ["string"],
  "dates_mentioned": ["string"],
  "topics": ["string"],
  "type": "observation|task|idea|reference|person_note",
  "source": "string"
}
Rules:
- Keep arrays concise.
- Use lowercase for type.
- If unsure, prefer "observation".
- Do not include any text outside the JSON object.`

type Client struct {
	name                  string
	baseURL               string
	apiKey                string
	embeddingModel        string
	metadataModel         string
	fallbackMetadataModel string
	temperature           float64
	headers               map[string]string
	httpClient            *http.Client
	log                   *slog.Logger
	dimensions            int
	logConversations      bool
}

type Config struct {
	Name                  string
	BaseURL               string
	APIKey                string
	EmbeddingModel        string
	MetadataModel         string
	FallbackMetadataModel string
	Temperature           float64
	Headers               map[string]string
	HTTPClient            *http.Client
	Log                   *slog.Logger
	Dimensions            int
	LogConversations      bool
}

type embeddingsRequest struct {
	Input string `json:"input"`
	Model string `json:"model"`
}

type embeddingsResponse struct {
	Data []struct {
		Embedding []float32 `json:"embedding"`
	} `json:"data"`
	Error *providerError `json:"error,omitempty"`
}

type chatCompletionsRequest struct {
	Model          string        `json:"model"`
	Temperature    float64       `json:"temperature,omitempty"`
	ResponseFormat *responseType `json:"response_format,omitempty"`
	Messages       []chatMessage `json:"messages"`
}

type responseType struct {
	Type string `json:"type"`
}

type chatMessage struct {
	Role    string `json:"role"`
	Content string `json:"content"`
}

type chatCompletionsResponse struct {
	Choices []struct {
		Message responseChatMessage `json:"message"`
		Text    string              `json:"text,omitempty"`
	} `json:"choices"`
	Error *providerError `json:"error,omitempty"`
}

type responseChatMessage struct {
	Role             string          `json:"role"`
	Content          json.RawMessage `json:"content"`
	ReasoningContent string          `json:"reasoning_content,omitempty"`
}

type providerError struct {
	Message string `json:"message"`
	Type    string `json:"type,omitempty"`
}

func New(cfg Config) *Client {
	return &Client{
		name:                  cfg.Name,
		baseURL:               cfg.BaseURL,
		apiKey:                cfg.APIKey,
		embeddingModel:        cfg.EmbeddingModel,
		metadataModel:         cfg.MetadataModel,
		fallbackMetadataModel: cfg.FallbackMetadataModel,
		temperature:           cfg.Temperature,
		headers:               cfg.Headers,
		httpClient:            cfg.HTTPClient,
		log:                   cfg.Log,
		dimensions:            cfg.Dimensions,
		logConversations:      cfg.LogConversations,
	}
}

func (c *Client) Embed(ctx context.Context, input string) ([]float32, error) {
	input = strings.TrimSpace(input)
	if input == "" {
		return nil, fmt.Errorf("%s embed: input must not be empty", c.name)
	}

	var resp embeddingsResponse
	err := c.doJSON(ctx, "/embeddings", embeddingsRequest{
		Input: input,
		Model: c.embeddingModel,
	}, &resp)
	if err != nil {
		return nil, err
	}
	if resp.Error != nil {
		return nil, fmt.Errorf("%s embed error: %s", c.name, resp.Error.Message)
	}
	if len(resp.Data) == 0 {
		return nil, fmt.Errorf("%s embed: no embedding returned", c.name)
	}
	if c.dimensions > 0 && len(resp.Data[0].Embedding) != c.dimensions {
		return nil, fmt.Errorf("%s embed: expected %d dimensions, got %d", c.name, c.dimensions, len(resp.Data[0].Embedding))
	}

	return resp.Data[0].Embedding, nil
}

func (c *Client) ExtractMetadata(ctx context.Context, input string) (thoughttypes.ThoughtMetadata, error) {
	input = strings.TrimSpace(input)
	if input == "" {
		return thoughttypes.ThoughtMetadata{}, fmt.Errorf("%s extract metadata: input must not be empty", c.name)
	}

	result, err := c.extractMetadataWithModel(ctx, input, c.metadataModel)
	if err != nil && c.fallbackMetadataModel != "" && ctx.Err() == nil {
		if c.log != nil {
			c.log.Warn("metadata extraction failed, trying fallback model",
				slog.String("provider", c.name),
				slog.String("primary_model", c.metadataModel),
				slog.String("fallback_model", c.fallbackMetadataModel),
				slog.String("error", err.Error()),
			)
		}
		return c.extractMetadataWithModel(ctx, input, c.fallbackMetadataModel)
	}
	return result, err
}

func (c *Client) extractMetadataWithModel(ctx context.Context, input, model string) (thoughttypes.ThoughtMetadata, error) {
	req := chatCompletionsRequest{
		Model:       model,
		Temperature: c.temperature,
		ResponseFormat: &responseType{
			Type: "json_object",
		},
		Messages: []chatMessage{
			{Role: "system", Content: metadataSystemPrompt},
			{Role: "user", Content: input},
		},
	}

	if c.logConversations && c.log != nil {
		c.log.Info("metadata conversation request",
			slog.String("provider", c.name),
			slog.String("model", model),
			slog.String("system", metadataSystemPrompt),
			slog.String("input", input),
		)
	}

	var resp chatCompletionsResponse
	if err := c.doJSON(ctx, "/chat/completions", req, &resp); err != nil {
		return thoughttypes.ThoughtMetadata{}, err
	}
	if resp.Error != nil {
		return thoughttypes.ThoughtMetadata{}, fmt.Errorf("%s metadata error: %s", c.name, resp.Error.Message)
	}
	if len(resp.Choices) == 0 {
		return thoughttypes.ThoughtMetadata{}, fmt.Errorf("%s metadata: no choices returned", c.name)
	}

	rawResponse := extractChoiceText(resp.Choices[0].Message, resp.Choices[0].Text)

	if c.logConversations && c.log != nil {
		c.log.Info("metadata conversation response",
			slog.String("provider", c.name),
			slog.String("model", model),
			slog.String("response", rawResponse),
		)
	}

	metadataText := strings.TrimSpace(rawResponse)
	metadataText = stripThinkingBlocks(metadataText)
	metadataText = stripCodeFence(metadataText)
	metadataText = extractJSONObject(metadataText)
	if metadataText == "" {
		return thoughttypes.ThoughtMetadata{}, fmt.Errorf("%s metadata: response contains no JSON object", c.name)
	}

	var metadata thoughttypes.ThoughtMetadata
	if err := json.Unmarshal([]byte(metadataText), &metadata); err != nil {
		return thoughttypes.ThoughtMetadata{}, fmt.Errorf("%s metadata: parse json: %w", c.name, err)
	}

	return metadata, nil
}

func (c *Client) Summarize(ctx context.Context, systemPrompt, userPrompt string) (string, error) {
	req := chatCompletionsRequest{
		Model:       c.metadataModel,
		Temperature: 0.2,
		Messages: []chatMessage{
			{Role: "system", Content: systemPrompt},
			{Role: "user", Content: userPrompt},
		},
	}

	var resp chatCompletionsResponse
	if err := c.doJSON(ctx, "/chat/completions", req, &resp); err != nil {
		return "", err
	}
	if resp.Error != nil {
		return "", fmt.Errorf("%s summarize error: %s", c.name, resp.Error.Message)
	}
	if len(resp.Choices) == 0 {
		return "", fmt.Errorf("%s summarize: no choices returned", c.name)
	}

	return extractChoiceText(resp.Choices[0].Message, resp.Choices[0].Text), nil
}

func (c *Client) Name() string {
	return c.name
}

func (c *Client) EmbeddingModel() string {
	return c.embeddingModel
}

func (c *Client) doJSON(ctx context.Context, path string, requestBody any, dest any) error {
	body, err := json.Marshal(requestBody)
	if err != nil {
		return fmt.Errorf("%s request marshal: %w", c.name, err)
	}

	const maxAttempts = 3

	var lastErr error
	for attempt := 1; attempt <= maxAttempts; attempt++ {
		req, err := http.NewRequestWithContext(ctx, http.MethodPost, strings.TrimRight(c.baseURL, "/")+path, bytes.NewReader(body))
		if err != nil {
			return fmt.Errorf("%s build request: %w", c.name, err)
		}

		req.Header.Set("Authorization", "Bearer "+c.apiKey)
		req.Header.Set("Content-Type", "application/json")
		req.Header.Set("Accept", "application/json")
		for key, value := range c.headers {
			if strings.TrimSpace(key) == "" || strings.TrimSpace(value) == "" {
				continue
			}
			req.Header.Set(key, value)
		}

		resp, err := c.httpClient.Do(req)
		if err != nil {
			lastErr = fmt.Errorf("%s request failed: %w", c.name, err)
			if attempt < maxAttempts && ctx.Err() == nil && isRetryableError(err) {
				if retryErr := sleepRetry(ctx, attempt, c.log, c.name); retryErr != nil {
					return retryErr
				}
				continue
			}
			return lastErr
		}

		payload, readErr := io.ReadAll(resp.Body)
		resp.Body.Close()
		if readErr != nil {
			lastErr = fmt.Errorf("%s read response: %w", c.name, readErr)
			if attempt < maxAttempts {
				if retryErr := sleepRetry(ctx, attempt, c.log, c.name); retryErr != nil {
					return retryErr
				}
				continue
			}
			return lastErr
		}

		if resp.StatusCode >= http.StatusBadRequest {
			lastErr = fmt.Errorf("%s request failed with status %d: %s", c.name, resp.StatusCode, strings.TrimSpace(string(payload)))
			if attempt < maxAttempts && isRetryableStatus(resp.StatusCode) {
				if retryErr := sleepRetry(ctx, attempt, c.log, c.name); retryErr != nil {
					return retryErr
				}
				continue
			}
			return lastErr
		}

		if err := json.Unmarshal(payload, dest); err != nil {
			if c.log != nil {
				c.log.Debug("provider response body", slog.String("provider", c.name), slog.String("body", string(payload)))
			}
			return fmt.Errorf("%s decode response: %w", c.name, err)
		}

		return nil
	}

	return lastErr
}

// extractJSONObject finds the first complete {...} block in s.
// It handles models that prepend prose to a JSON response despite json_object mode.
func extractJSONObject(s string) string {
	for start := 0; start < len(s); start++ {
		if s[start] != '{' {
			continue
		}
		depth := 0
		inString := false
		escaped := false
		for end := start; end < len(s); end++ {
			ch := s[end]
			if escaped {
				escaped = false
				continue
			}
			if ch == '\\' && inString {
				escaped = true
				continue
			}
			if ch == '"' {
				inString = !inString
				continue
			}
			if inString {
				continue
			}
			switch ch {
			case '{':
				depth++
			case '}':
				depth--
				if depth == 0 {
					candidate := s[start : end+1]
					if json.Valid([]byte(candidate)) {
						return candidate
					}
				}
			}
		}
	}
	return ""
}

// stripThinkingBlocks removes <think>...</think> and <thinking>...</thinking>
// blocks produced by reasoning models (DeepSeek R1, QwQ, etc.) so that the
// remaining text can be parsed as JSON without interference from thinking content
// that may itself contain braces.
func stripThinkingBlocks(s string) string {
	for _, tag := range []string{"think", "thinking"} {
		open := "<" + tag + ">"
		close := "</" + tag + ">"
		for {
			start := strings.Index(s, open)
			if start == -1 {
				break
			}
			end := strings.Index(s[start:], close)
			if end == -1 {
				s = s[:start]
				break
			}
			s = s[:start] + s[start+end+len(close):]
		}
	}
	return strings.TrimSpace(s)
}

func stripCodeFence(value string) string {
	value = strings.TrimSpace(value)
	if !strings.HasPrefix(value, "```") {
		return value
	}

	value = strings.TrimPrefix(value, "```json")
	value = strings.TrimPrefix(value, "```")
	value = strings.TrimSuffix(value, "```")
	return strings.TrimSpace(value)
}

func extractChoiceText(message responseChatMessage, fallbackText string) string {
	if text := strings.TrimSpace(extractMessageContent(message.Content)); text != "" {
		return text
	}
	if text := strings.TrimSpace(message.ReasoningContent); text != "" {
		return text
	}
	return strings.TrimSpace(fallbackText)
}

func extractMessageContent(raw json.RawMessage) string {
	raw = bytes.TrimSpace(raw)
	if len(raw) == 0 {
		return ""
	}

	var contentString string
	if err := json.Unmarshal(raw, &contentString); err == nil {
		return contentString
	}

	var contentArray []any
	if err := json.Unmarshal(raw, &contentArray); err == nil {
		parts := make([]string, 0, len(contentArray))
		for _, item := range contentArray {
			if text := strings.TrimSpace(extractTextFromAny(item)); text != "" {
				parts = append(parts, text)
			}
		}
		return strings.Join(parts, "\n")
	}

	var contentObject map[string]any
	if err := json.Unmarshal(raw, &contentObject); err == nil {
		return extractTextFromAny(contentObject)
	}

	return strings.TrimSpace(string(raw))
}

func extractTextFromAny(value any) string {
	switch typed := value.(type) {
	case string:
		return typed
	case []any:
		parts := make([]string, 0, len(typed))
		for _, item := range typed {
			if text := strings.TrimSpace(extractTextFromAny(item)); text != "" {
				parts = append(parts, text)
			}
		}
		return strings.Join(parts, "\n")
	case map[string]any:
		// Common provider shapes for chat content parts.
		for _, key := range []string{"text", "output_text", "content", "value"} {
			if nested, ok := typed[key]; ok {
				if text := strings.TrimSpace(extractTextFromAny(nested)); text != "" {
					return text
				}
			}
		}
	}
	return ""
}

func isRetryableStatus(status int) bool {
	switch status {
	case http.StatusTooManyRequests, http.StatusInternalServerError, http.StatusBadGateway, http.StatusServiceUnavailable, http.StatusGatewayTimeout:
		return true
	default:
		return false
	}
}

func isRetryableError(err error) bool {
	if err == nil {
		return false
	}
	if errors.Is(err, context.DeadlineExceeded) || errors.Is(err, context.Canceled) {
		return true
	}
	var netErr net.Error
	return errors.As(err, &netErr)
}

func sleepRetry(ctx context.Context, attempt int, log *slog.Logger, provider string) error {
	delay := time.Duration(attempt*attempt) * 200 * time.Millisecond
	if log != nil {
		log.Warn("retrying provider request", slog.String("provider", provider), slog.Duration("delay", delay), slog.Int("attempt", attempt+1))
	}
	timer := time.NewTimer(delay)
	defer timer.Stop()
	select {
	case <-ctx.Done():
		return ctx.Err()
	case <-timer.C:
		return nil
	}
}