package analyzer

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

type DeepSeekAnalyzer struct {
	apiKey  string
	baseURL string
	client  *http.Client
}

func NewDeepSeekAnalyzer(apiKey, baseURL string) *DeepSeekAnalyzer {
	if baseURL == "" {
		baseURL = "https://api.deepseek.com"
	}
	return &DeepSeekAnalyzer{
		apiKey:  apiKey,
		baseURL: strings.TrimRight(baseURL, "/"),
		client:  &http.Client{Timeout: 30 * time.Second},
	}
}

func (d *DeepSeekAnalyzer) AnalyzeJD(ctx context.Context, jobTitle, rawContent string) (*AnalysisOutput, error) {
	prompt := fmt.Sprintf(`You are an expert technical resume screener. Analyze the following job description for the title "%s".
Provide a structured JSON output with 3 fields:
- "matched_highlights": list of 3-5 core technical skills/requirements matched (e.g. ["Go (Golang)", "Microservices", "REST APIs"]).
- "missing_highlights": list of 1-3 missing skills, experience gaps, or extra requirements (e.g. ["10+ yrs experience", "Kubernetes administration"]).
- "tailoring_suggestions": list of 2-3 specific action points for tailoring a resume to this JD.

Job Title: %s
Job Content:
%s`, jobTitle, jobTitle, rawContent)

	reqBody := map[string]interface{}{
		"model": "deepseek-chat",
		"messages": []map[string]string{
			{"role": "system", "content": "You are a professional hiring assistant. You MUST respond ONLY with valid JSON matching {\"matched_highlights\": [...], \"missing_highlights\": [...], \"tailoring_suggestions\": [...]}."},
			{"role": "user", "content": prompt},
		},
		"response_format": map[string]string{
			"type": "json_object",
		},
	}

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

	url := fmt.Sprintf("%s/chat/completions", d.baseURL)
	req, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewBuffer(jsonBytes))
	if err != nil {
		return nil, fmt.Errorf("failed to create DeepSeek request: %w", err)
	}

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

	resp, err := d.client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("DeepSeek API call failed: %w", err)
	}
	defer resp.Body.Close()

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

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("DeepSeek API error (status %d): %s", resp.StatusCode, string(respBytes))
	}

	var dsResp struct {
		Choices []struct {
			Message struct {
				Content string `json:"content"`
			} `json:"message"`
		} `json:"choices"`
	}

	if err := json.Unmarshal(respBytes, &dsResp); err != nil {
		return nil, fmt.Errorf("failed to decode DeepSeek envelope: %w", err)
	}

	if len(dsResp.Choices) == 0 {
		return nil, fmt.Errorf("empty choices in DeepSeek response")
	}

	rawJSON := cleanJSONResponse(dsResp.Choices[0].Message.Content)

	var output AnalysisOutput
	if err := json.Unmarshal([]byte(rawJSON), &output); err != nil {
		return nil, fmt.Errorf("failed to parse DeepSeek JSON output: %w", err)
	}

	return &output, nil
}

func cleanJSONResponse(raw string) string {
	cleaned := strings.TrimSpace(raw)
	if strings.HasPrefix(cleaned, "```json") {
		cleaned = strings.TrimPrefix(cleaned, "```json")
		cleaned = strings.TrimSuffix(cleaned, "```")
	} else if strings.HasPrefix(cleaned, "```") {
		cleaned = strings.TrimPrefix(cleaned, "```")
		cleaned = strings.TrimSuffix(cleaned, "```")
	}
	return strings.TrimSpace(cleaned)
}