package analyzer

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

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

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

func (d *DeepSeekAnalyzer) buildUserPrompt(jobTitle, rawContent string) string {
	if d.userPromptTemplate == "" {
		return fmt.Sprintf("Analyze the following job description for candidate Pengzhan Hao.\n\nJob Title: %s\n\nJob Description:\n%s\n\nProvide the structured evaluation adhering to the JSON schema.", jobTitle, rawContent)
	}
	res := strings.ReplaceAll(d.userPromptTemplate, "{{.JobTitle}}", jobTitle)
	res = strings.ReplaceAll(res, "{{.JobContent}}", rawContent)
	return res
}

func (d *DeepSeekAnalyzer) AnalyzeJD(ctx context.Context, jobTitle, rawContent string) (*AnalysisOutput, error) {
	sysPrompt := d.systemPrompt
	if sysPrompt == "" {
		sysPrompt = "You are an expert technical resume screener. You MUST respond with a valid JSON object matching {\"ai_score\": 80.0, \"is_qualified\": true, \"summary\": \"...\", \"matched_highlights\": [...], \"missing_highlights\": [...], \"tailoring_suggestions\": [...]}."
	}

	userPrompt := d.buildUserPrompt(jobTitle, rawContent)

	reqBody := map[string]interface{}{
		"model": "deepseek-chat",
		"messages": []map[string]string{
			{"role": "system", "content": sysPrompt},
			{"role": "user", "content": userPrompt},
		},
		"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 func() { _ = 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 (content: %s)", err, rawJSON)
	}

	// Sanitize output bounds
	if output.AIScore < 0 {
		output.AIScore = 0
	} else if output.AIScore > 100 {
		output.AIScore = 100
	}

	if output.AIScore >= 60.0 {
		output.IsQualified = true
	}

	if output.MatchedHighlights == nil {
		output.MatchedHighlights = []string{}
	}
	if output.MissingHighlights == nil {
		output.MissingHighlights = []string{}
	}
	if output.TailoringSuggestions == nil {
		output.TailoringSuggestions = []string{}
	}

	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)
}