package analyzer

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

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

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

func (g *GeminiAnalyzer) 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

Respond STRICTLY with valid JSON matching the format:
{"matched_highlights": [...], "missing_highlights": [...], "tailoring_suggestions": [...]}`, jobTitle, jobTitle, rawContent)

	reqBody := map[string]interface{}{
		"contents": []map[string]interface{}{
			{
				"parts": []map[string]string{
					{"text": prompt},
				},
			},
		},
		"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)
	}

	return &output, nil
}