//
//  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
//
//  Licensed under the Apache License, Version 2.0 (the "License");
//  you may not use this file except in compliance with the License.
//  You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
//  Unless required by applicable law or agreed to in writing, software
//  distributed under the License is distributed on an "AS IS" BASIS,
//  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
//  See the License for the specific language governing permissions and
//  limitations under the License.
//

package models

import (
	"bufio"
	"bytes"
	"context"
	"encoding/base64"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"strings"
	"time"
)

// MistralModel implements ModelDriver for Mistral AI.
//
// Mistral exposes an OpenAI-compatible REST API at https://api.mistral.ai/v1
// (chat completions at /chat/completions, list models at /models). The wire
// shape matches OpenAI closely enough that the chat path here is a direct
// port of the OpenAI driver, with the differences kept small on purpose:
// no reasoning_content pass-through (Mistral does not expose one), and a
// distinct Name() so the factory can route to this driver.
type MistralModel struct {
	BaseURL    map[string]string
	URLSuffix  URLSuffix
	httpClient *http.Client
}

// NewMistralModel creates a new Mistral model instance.
//
// We clone http.DefaultTransport so we keep Go's defaults for
// ProxyFromEnvironment, DialContext (with KeepAlive), HTTP/2,
// TLSHandshakeTimeout, and ExpectContinueTimeout, and only override
// the connection-pool fields we care about.
//
// The Client itself has no Timeout. http.Client.Timeout would also
// cap the time spent reading the response body, which would cut off
// long-lived SSE streams in ChatStreamlyWithSender. Non-streaming
// callers wrap each request with context.WithTimeout instead.
func NewMistralModel(baseURL map[string]string, urlSuffix URLSuffix) *MistralModel {
	transport := http.DefaultTransport.(*http.Transport).Clone()
	transport.MaxIdleConns = 100
	transport.MaxIdleConnsPerHost = 10
	transport.IdleConnTimeout = 90 * time.Second
	transport.DisableCompression = false
	transport.ResponseHeaderTimeout = 60 * time.Second

	return &MistralModel{
		BaseURL:   baseURL,
		URLSuffix: urlSuffix,
		httpClient: &http.Client{
			Transport: transport,
		},
	}
}

func (m *MistralModel) NewInstance(baseURL map[string]string) ModelDriver {
	return NewMistralModel(baseURL, m.URLSuffix)
}

func (m *MistralModel) Name() string {
	return "mistral"
}

// baseURLForRegion returns the base URL for the given region, or an
// error if no entry exists. This makes a misconfigured region fail
// fast with a clear message, instead of silently producing a relative
// URL that the HTTP transport then rejects.
func (m *MistralModel) baseURLForRegion(region string) (string, error) {
	base, ok := m.BaseURL[region]
	if !ok || base == "" {
		return "", fmt.Errorf("mistral: no base URL configured for region %q", region)
	}
	return base, nil
}

// ChatWithMessages sends multiple messages with roles and returns the response.
func (m *MistralModel) ChatWithMessages(modelName string, messages []Message, apiConfig *APIConfig, chatModelConfig *ChatConfig) (*ChatResponse, error) {
	if apiConfig == nil || apiConfig.ApiKey == nil || *apiConfig.ApiKey == "" {
		return nil, fmt.Errorf("api key is required")
	}

	if len(messages) == 0 {
		return nil, fmt.Errorf("messages is empty")
	}

	region := "default"
	if apiConfig.Region != nil && *apiConfig.Region != "" {
		region = *apiConfig.Region
	}

	baseURL, err := m.baseURLForRegion(region)
	if err != nil {
		return nil, err
	}
	url := fmt.Sprintf("%s/%s", baseURL, m.URLSuffix.Chat)

	apiMessages := make([]map[string]interface{}, len(messages))
	for i, msg := range messages {
		apiMessages[i] = map[string]interface{}{
			"role":    msg.Role,
			"content": msg.Content,
		}
	}

	reqBody := map[string]interface{}{
		"model":    modelName,
		"messages": apiMessages,
		"stream":   false,
	}

	// Note: do NOT propagate chatModelConfig.Stream into the request body
	// here. ChatWithMessages parses a single JSON response, so stream must
	// always be off for this code path.
	if chatModelConfig != nil {
		if chatModelConfig.MaxTokens != nil {
			reqBody["max_tokens"] = *chatModelConfig.MaxTokens
		}
		if chatModelConfig.Temperature != nil {
			reqBody["temperature"] = *chatModelConfig.Temperature
		}
		if chatModelConfig.TopP != nil {
			reqBody["top_p"] = *chatModelConfig.TopP
		}
		if chatModelConfig.Stop != nil {
			reqBody["stop"] = *chatModelConfig.Stop
		}
	}

	jsonData, err := json.Marshal(reqBody)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal request: %w", err)
	}

	ctx, cancel := context.WithTimeout(context.Background(), nonStreamCallTimeout)
	defer cancel()

	req, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewBuffer(jsonData))
	if err != nil {
		return nil, fmt.Errorf("failed to create request: %w", err)
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", *apiConfig.ApiKey))

	resp, err := m.httpClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("failed to send request: %w", err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("API request failed with status %d: %s", resp.StatusCode, string(body))
	}

	var result map[string]interface{}
	if err = json.Unmarshal(body, &result); err != nil {
		return nil, fmt.Errorf("failed to parse response: %w", err)
	}

	choices, ok := result["choices"].([]interface{})
	if !ok || len(choices) == 0 {
		return nil, fmt.Errorf("no choices in response")
	}

	firstChoice, ok := choices[0].(map[string]interface{})
	if !ok {
		return nil, fmt.Errorf("invalid choice format")
	}

	messageMap, ok := firstChoice["message"].(map[string]interface{})
	if !ok {
		return nil, fmt.Errorf("invalid message format")
	}

	content, reasonContent, err := extractMistralContent(messageMap["content"])
	if err != nil {
		return nil, err
	}

	return &ChatResponse{
		Answer:        &content,
		ReasonContent: &reasonContent,
	}, nil
}

// extractMistralContent normalizes the two shapes Mistral can return in
// choices[0].message.content.
//
//  1. Plain string. The historical shape, used by every non-reasoning
//     Mistral model (mistral-large, mistral-medium, ministral-*, etc.):
//
//     "content": "Pong."
//
//  2. Structured array of typed parts. Used by the magistral reasoning
//     family (magistral-small-*, magistral-medium-*) when the model
//     actually produces a chain-of-thought:
//
//     "content": [
//     {"type": "thinking", "thinking": [{"type": "text", "text": "..."}]},
//     {"type": "text", "text": "The final answer is ..."}
//     ]
//
// The function concatenates the visible text parts into the assistant
// answer and the inner thinking text into the reasoning trace. Unknown
// part types are skipped rather than failing, so a new part shape from
// Mistral does not break the driver for tenants that don't use it.
func extractMistralContent(raw interface{}) (string, string, error) {
	switch v := raw.(type) {
	case string:
		return v, "", nil
	case []interface{}:
		var answer, reasoning strings.Builder
		for _, part := range v {
			pm, ok := part.(map[string]interface{})
			if !ok {
				continue
			}
			switch pm["type"] {
			case "text":
				if t, ok := pm["text"].(string); ok {
					answer.WriteString(t)
				}
			case "thinking":
				// thinking is an array of inner text parts; concatenate
				// any inner element with a non-empty text field.
				inner, ok := pm["thinking"].([]interface{})
				if !ok {
					continue
				}
				for _, sub := range inner {
					sm, ok := sub.(map[string]interface{})
					if !ok {
						continue
					}
					if t, ok := sm["text"].(string); ok {
						reasoning.WriteString(t)
					}
				}
			}
		}
		return answer.String(), reasoning.String(), nil
	case nil:
		return "", "", nil
	default:
		return "", "", fmt.Errorf("mistral: unsupported content type %T", raw)
	}
}

// ChatStreamlyWithSender sends messages and streams the response via the
// sender function. The Mistral SSE stream uses the same shape as OpenAI:
// "data:" lines carrying JSON events, with a final "[DONE]" line.
func (m *MistralModel) ChatStreamlyWithSender(modelName string, messages []Message, apiConfig *APIConfig, chatModelConfig *ChatConfig, sender func(*string, *string) error) error {
	if sender == nil {
		return fmt.Errorf("sender is required")
	}

	if len(messages) == 0 {
		return fmt.Errorf("messages is empty")
	}

	if apiConfig == nil || apiConfig.ApiKey == nil || *apiConfig.ApiKey == "" {
		return fmt.Errorf("api key is required")
	}

	var region = "default"
	if apiConfig.Region != nil && *apiConfig.Region != "" {
		region = *apiConfig.Region
	}

	baseURL, err := m.baseURLForRegion(region)
	if err != nil {
		return err
	}
	url := fmt.Sprintf("%s/%s", baseURL, m.URLSuffix.Chat)

	apiMessages := make([]map[string]interface{}, len(messages))
	for i, msg := range messages {
		apiMessages[i] = map[string]interface{}{
			"role":    msg.Role,
			"content": msg.Content,
		}
	}

	reqBody := map[string]interface{}{
		"model":    modelName,
		"messages": apiMessages,
		"stream":   true,
	}

	if chatModelConfig != nil {
		// Refuse to run if the caller explicitly asked for stream=false.
		// The body of this method only knows how to read SSE, so a
		// non-SSE JSON response would be parsed as if it were a stream
		// and produce no chunks. Better to fail clearly.
		if chatModelConfig.Stream != nil && !*chatModelConfig.Stream {
			return fmt.Errorf("stream must be true in ChatStreamlyWithSender")
		}

		if chatModelConfig.MaxTokens != nil {
			reqBody["max_tokens"] = *chatModelConfig.MaxTokens
		}
		if chatModelConfig.Temperature != nil {
			reqBody["temperature"] = *chatModelConfig.Temperature
		}
		if chatModelConfig.TopP != nil {
			reqBody["top_p"] = *chatModelConfig.TopP
		}
		if chatModelConfig.Stop != nil {
			reqBody["stop"] = *chatModelConfig.Stop
		}
	}

	jsonData, err := json.Marshal(reqBody)
	if err != nil {
		return fmt.Errorf("failed to marshal request: %w", err)
	}

	// Use an explicit background context. SSE streams are long-lived
	// so we do not attach a hard deadline here; the transport's
	// ResponseHeaderTimeout caps the connection-establishment phase.
	req, err := http.NewRequestWithContext(context.Background(), "POST", url, bytes.NewBuffer(jsonData))
	if err != nil {
		return fmt.Errorf("failed to create request: %w", err)
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", *apiConfig.ApiKey))

	resp, err := m.httpClient.Do(req)
	if err != nil {
		return fmt.Errorf("failed to send request: %w", err)
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		body, _ := io.ReadAll(resp.Body)
		return fmt.Errorf("API request failed with status %d: %s", resp.StatusCode, string(body))
	}

	// SSE parsing: bump the scanner buffer from the 64KB default to 1MB
	// so we never silently truncate a long data: line.
	scanner := bufio.NewScanner(resp.Body)
	scanner.Buffer(make([]byte, 64*1024), 1024*1024)
	sawTerminal := false
	for scanner.Scan() {
		line := scanner.Text()

		if !strings.HasPrefix(line, "data:") {
			continue
		}

		data := strings.TrimSpace(line[5:])

		if data == "[DONE]" {
			sawTerminal = true
			break
		}

		var event map[string]interface{}
		if err = json.Unmarshal([]byte(data), &event); err != nil {
			continue
		}

		choices, ok := event["choices"].([]interface{})
		if !ok || len(choices) == 0 {
			continue
		}

		firstChoice, ok := choices[0].(map[string]interface{})
		if !ok {
			continue
		}

		delta, ok := firstChoice["delta"].(map[string]interface{})
		if !ok {
			continue
		}

		content, ok := delta["content"].(string)
		if ok && content != "" {
			if err := sender(&content, nil); err != nil {
				return err
			}
		}

		finishReason, ok := firstChoice["finish_reason"].(string)
		if ok && finishReason != "" {
			sawTerminal = true
			break
		}
	}

	if err := scanner.Err(); err != nil {
		return fmt.Errorf("failed to scan response body: %w", err)
	}
	if !sawTerminal {
		return fmt.Errorf("mistral: stream ended before [DONE] or finish_reason")
	}

	endOfStream := "[DONE]"
	if err := sender(&endOfStream, nil); err != nil {
		return err
	}

	return nil
}

type mistralEmbeddingData struct {
	Embedding []float64 `json:"embedding"`
	Object    string    `json:"object"`
	Index     int       `json:"index"`
}

type mistralEmbeddingResponse struct {
	Data   []mistralEmbeddingData `json:"data"`
	Model  string                 `json:"model"`
	Object string                 `json:"object"`
}

// Embed turns a list of texts into embedding vectors using the
// Mistral /v1/embeddings endpoint (mistral-embed). The output has
// one vector per input, in the same order the inputs were given.
func (m *MistralModel) Embed(modelName *string, texts []string, apiConfig *APIConfig, embeddingConfig *EmbeddingConfig) ([]EmbeddingData, error) {
	if len(texts) == 0 {
		return []EmbeddingData{}, nil
	}

	if apiConfig == nil || apiConfig.ApiKey == nil || *apiConfig.ApiKey == "" {
		return nil, fmt.Errorf("api key is required")
	}

	if modelName == nil || *modelName == "" {
		return nil, fmt.Errorf("model name is required")
	}

	region := "default"
	if apiConfig.Region != nil && *apiConfig.Region != "" {
		region = *apiConfig.Region
	}

	baseURL, err := m.baseURLForRegion(region)
	if err != nil {
		return nil, err
	}
	url := fmt.Sprintf("%s/%s", baseURL, m.URLSuffix.Embedding)

	reqBody := map[string]interface{}{
		"model": *modelName,
		"input": texts,
	}

	jsonData, err := json.Marshal(reqBody)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal request: %w", err)
	}

	ctx, cancel := context.WithTimeout(context.Background(), nonStreamCallTimeout)
	defer cancel()

	req, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewBuffer(jsonData))
	if err != nil {
		return nil, fmt.Errorf("failed to create request: %w", err)
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", *apiConfig.ApiKey))

	resp, err := m.httpClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("failed to send request: %w", err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("Mistral embeddings API error: %s, body: %s", resp.Status, string(body))
	}

	var parsed mistralEmbeddingResponse
	if err = json.Unmarshal(body, &parsed); err != nil {
		return nil, fmt.Errorf("failed to parse response: %w", err)
	}

	// Reorder the returned vectors by their reported index so the output
	// always lines up with the input texts, even if the upstream API ever
	// returns items out of order. A nil slot at the end indicates the
	// upstream did not return an embedding for that input.
	embeddings := make([]EmbeddingData, len(texts))
	filled := make([]bool, len(texts))
	for _, item := range parsed.Data {
		if item.Index < 0 || item.Index >= len(texts) {
			return nil, fmt.Errorf("mistral: response index %d out of range for %d inputs", item.Index, len(texts))
		}
		if filled[item.Index] {
			// A malformed response that repeats the same index would
			// silently overwrite the earlier vector. Fail loudly so
			// the caller never uses ambiguous output.
			return nil, fmt.Errorf("mistral: duplicate embedding index %d in response", item.Index)
		}
		embeddings[item.Index] = EmbeddingData{
			Embedding: item.Embedding,
			Index:     item.Index,
		}
		filled[item.Index] = true
	}
	for i, ok := range filled {
		if !ok {
			return nil, fmt.Errorf("mistral: missing embedding for input index %d", i)
		}
	}

	return embeddings, nil
}

// ListModels returns the list of model ids visible to the API key.
func (m *MistralModel) ListModels(apiConfig *APIConfig) ([]string, error) {
	if apiConfig == nil || apiConfig.ApiKey == nil || *apiConfig.ApiKey == "" {
		return nil, fmt.Errorf("api key is required")
	}

	region := "default"
	if apiConfig.Region != nil && *apiConfig.Region != "" {
		region = *apiConfig.Region
	}

	baseURL, err := m.baseURLForRegion(region)
	if err != nil {
		return nil, err
	}
	url := fmt.Sprintf("%s/%s", baseURL, m.URLSuffix.Models)

	ctx, cancel := context.WithTimeout(context.Background(), nonStreamCallTimeout)
	defer cancel()

	req, err := http.NewRequestWithContext(ctx, "GET", url, nil)
	if err != nil {
		return nil, fmt.Errorf("failed to create request: %w", err)
	}

	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", *apiConfig.ApiKey))

	resp, err := m.httpClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("failed to send request: %w", err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("API request failed with status %d: %s", resp.StatusCode, string(body))
	}

	var result map[string]interface{}
	if err = json.Unmarshal(body, &result); err != nil {
		return nil, fmt.Errorf("failed to parse response: %w", err)
	}

	data, ok := result["data"].([]interface{})
	if !ok {
		return nil, fmt.Errorf("invalid models list format")
	}

	models := make([]string, 0)
	for _, model := range data {
		modelMap, ok := model.(map[string]interface{})
		if !ok {
			continue
		}
		modelName, ok := modelMap["id"].(string)
		if !ok {
			continue
		}
		models = append(models, modelName)
	}

	return models, nil
}

// Balance is not exposed by the Mistral API, so this returns "no such method".
func (m *MistralModel) Balance(apiConfig *APIConfig) (map[string]interface{}, error) {
	return nil, fmt.Errorf("no such method")
}

// CheckConnection runs a lightweight ListModels call to verify the API key.
func (m *MistralModel) CheckConnection(apiConfig *APIConfig) error {
	_, err := m.ListModels(apiConfig)
	if err != nil {
		return err
	}
	return nil
}

// Rerank calculates similarity scores between query and documents. Mistral
// does not expose a public rerank API, so this returns "no such method".
func (m *MistralModel) Rerank(modelName *string, query string, documents []string, apiConfig *APIConfig, rerankConfig *RerankConfig) (*RerankResponse, error) {
	return nil, fmt.Errorf("no such method")
}

// TranscribeAudio transcribe audio
func (z *MistralModel) TranscribeAudio(modelName *string, file *string, apiConfig *APIConfig, asrConfig *ASRConfig) (*ASRResponse, error) {
	return nil, fmt.Errorf("%s, no such method", z.Name())
}

func (z *MistralModel) TranscribeAudioWithSender(modelName *string, file *string, apiConfig *APIConfig, asrConfig *ASRConfig, sender func(*string, *string) error) error {
	return fmt.Errorf("%s, no such method", z.Name())
}

// AudioSpeech convert text to audio
func (z *MistralModel) AudioSpeech(modelName *string, audioContent *string, apiConfig *APIConfig, ttsConfig *TTSConfig) (*TTSResponse, error) {
	return nil, fmt.Errorf("%s, no such method", z.Name())
}

func (z *MistralModel) AudioSpeechWithSender(modelName *string, audioContent *string, apiConfig *APIConfig, ttsConfig *TTSConfig, sender func(*string, *string) error) error {
	return fmt.Errorf("%s, no such method", z.Name())
}

// OCRFile OCR file
func (z *MistralModel) OCRFile(modelName *string, content []byte, urls *string, apiConfig *APIConfig, ocrConfig *OCRConfig) (*OCRFileResponse, error) {
	if (urls == nil || *urls == "") && (content == nil || len(content) == 0) {
		return nil, fmt.Errorf("file url or content is required")
	}

	region := "default"
	if apiConfig.Region != nil && *apiConfig.Region != "" {
		region = *apiConfig.Region
	}

	url := fmt.Sprintf("%s/%s", z.BaseURL[region], z.URLSuffix.OCR)

	var docURL string
	if urls != nil && *urls != "" {
		docURL = *urls
	} else {
		mimeType := http.DetectContentType(content)
		base64Str := base64.StdEncoding.EncodeToString(content)
		docURL = fmt.Sprintf("data:%s;base64,%s", mimeType, base64Str)
	}

	reqData := map[string]interface{}{
		"model": *modelName,
		"document": map[string]interface{}{
			"type":         "document_url",
			"document_url": docURL,
		},
	}

	jsonData, err := json.Marshal(reqData)
	if err != nil {
		return nil, fmt.Errorf("failed to marshal json payload: %w", err)
	}

	ctx, cancel := context.WithTimeout(context.Background(), 120*time.Second)
	defer cancel()

	req, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewBuffer(jsonData))
	if err != nil {
		return nil, fmt.Errorf("failed to create request: %w", err)
	}

	req.Header.Set("Content-Type", "application/json")
	req.Header.Set("Authorization", fmt.Sprintf("Bearer %s", *apiConfig.ApiKey))

	resp, err := z.httpClient.Do(req)
	if err != nil {
		return nil, fmt.Errorf("failed to send request: %w", err)
	}
	defer resp.Body.Close()

	body, err := io.ReadAll(resp.Body)
	if err != nil {
		return nil, fmt.Errorf("failed to read response: %w", err)
	}

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("Mistral OCR API error: %s, body: %s", resp.Status, string(body))
	}

	var mistralResp struct {
		Pages []struct {
			Index    int    `json:"index"`
			Markdown string `json:"markdown"`
		} `json:"pages"`
	}

	if err = json.Unmarshal(body, &mistralResp); err != nil {
		return nil, fmt.Errorf("failed to parse response json: %w", err)
	}

	var fullMarkdown strings.Builder
	for _, page := range mistralResp.Pages {
		fullMarkdown.WriteString(page.Markdown)
		fullMarkdown.WriteString("\n\n")
	}

	resultText := strings.TrimSpace(fullMarkdown.String())

	return &OCRFileResponse{
		Text: &resultText,
	}, nil
}

func (z *MistralModel) ParseFile(modelName *string, content []byte, url *string, apiConfig *APIConfig, parseFileConfig *ParseFileConfig) (*ParseFileResponse, error) {
	//TODO implement me
	panic("implement me")
}

func (z *MistralModel) ListTasks(apiConfig *APIConfig) ([]ListTaskStatus, error) {
	return nil, fmt.Errorf("%s, no such method", z.Name())
}

func (z *MistralModel) ShowTask(taskID string, apiConfig *APIConfig) (*TaskResponse, error) {
	return nil, fmt.Errorf("%s, no such method", z.Name())
}
