package analyzer

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

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

func NewGeminiAnalyzer(apiKey, systemPrompt, userPromptTemplate string) *GeminiAnalyzer {
	return &GeminiAnalyzer{
		apiKey:             apiKey,
		systemPrompt:       systemPrompt,
		userPromptTemplate: userPromptTemplate,
		client:             &http.Client{Timeout: 30 * time.Second},
	}
}

func (g *GeminiAnalyzer) buildUserPrompt(jobTitle, rawContent string) string {
	if g.userPromptTemplate == "" {
		return fmt.Sprintf("Analyze the following job description for candidate Pengzhan Hao.\n\nJob Title: %s\n\nJob Content:\n%s\n\nRespond with structured JSON.", jobTitle, rawContent)
	}
	res := strings.ReplaceAll(g.userPromptTemplate, "{{.JobTitle}}", jobTitle)
	res = strings.ReplaceAll(res, "{{.JobContent}}", rawContent)
	return res
}

func (g *GeminiAnalyzer) AnalyzeJD(ctx context.Context, jobTitle, rawContent string) (*AnalysisOutput, error) {
	sysPrompt := g.systemPrompt
	if sysPrompt == "" {
		sysPrompt = "You are an expert technical resume screener. Respond STRICTLY with valid JSON matching {\"ai_score\": 85.0, \"is_qualified\": true, \"summary\": \"...\", \"matched_highlights\": [...], \"missing_highlights\": [...], \"tailoring_suggestions\": [...]}."
	}

	userPrompt := g.buildUserPrompt(jobTitle, rawContent)
	fullPrompt := fmt.Sprintf("%s\n\n%s", sysPrompt, userPrompt)

	reqBody := map[string]interface{}{
		"contents": []map[string]interface{}{
			{
				"parts": []map[string]string{
					{"text": fullPrompt},
				},
			},
		},
		"generationConfig": map[string]interface{}{
			"response_mime_type": "application/json",
		},
	}

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

	url := fmt.Sprintf("https://generativelanguage.googleapis.com/v1beta/models/gemini-1.5-flash:generateContent?key=%s", g.apiKey)
	req, err := http.NewRequestWithContext(ctx, "POST", url, bytes.NewBuffer(jsonBytes))
	if err != nil {
		return nil, fmt.Errorf("failed to create Gemini HTTP request: %w", err)
	}
	req.Header.Set("Content-Type", "application/json")

	resp, err := g.client.Do(req)
	if err != nil {
		return nil, fmt.Errorf("gemini 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 Gemini response: %w", err)
	}

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

	var geminiResp struct {
		Candidates []struct {
			Content struct {
				Parts []struct {
					Text string `json:"text"`
				} `json:"parts"`
			} `json:"content"`
		} `json:"candidates"`
	}

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

	if len(geminiResp.Candidates) == 0 || len(geminiResp.Candidates[0].Content.Parts) == 0 {
		return nil, fmt.Errorf("empty candidates in Gemini response")
	}

	rawJSON := geminiResp.Candidates[0].Content.Parts[0].Text
	rawJSON = cleanJSONResponse(rawJSON)

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

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

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

	return &output, nil
}