package service

import (
	"encoding/csv"
	"fmt"
	"io"
	"os"
	"strings"

	"AI-Expert-Sidebar/internal/database"
	"AI-Expert-Sidebar/internal/models"
)

// ImportResult summarises the outcome of a CSV import.
type ImportResult struct {
	Imported int    `json:"imported"`
	Skipped  int    `json:"skipped"`
	Error    string `json:"error,omitempty"`
}

// ImportCSV reads a CSV file and inserts records into the active knowledge library.
//
// Required columns (case-insensitive): keyword, question, answer
// Optional column: category (defaults to "通用")
//
// The first row must be the header.
func ImportCSV(filePath string) ImportResult {
	f, err := os.Open(filePath)
	if err != nil {
		return ImportResult{Error: fmt.Sprintf("无法打开文件: %v", err)}
	}
	defer f.Close()

	db := database.Get()
	if db == nil {
		return ImportResult{Error: "知识库未初始化"}
	}

	r := csv.NewReader(f)
	r.TrimLeadingSpace = true
	r.LazyQuotes = true

	// Read and normalise header
	header, err := r.Read()
	if err != nil {
		return ImportResult{Error: fmt.Sprintf("读取表头失败: %v", err)}
	}
	colIdx := make(map[string]int)
	for i, h := range header {
		colIdx[strings.ToLower(strings.TrimSpace(h))] = i
	}
	for _, required := range []string{"keyword", "question", "answer"} {
		if _, ok := colIdx[required]; !ok {
			return ImportResult{Error: fmt.Sprintf("CSV 缺少必需列: %q (需要: keyword, question, answer)", required)}
		}
	}
	catIdx, hasCat := colIdx["category"]

	var imported, skipped int
	for {
		row, err := r.Read()
		if err == io.EOF {
			break
		}
		if err != nil {
			skipped++
			continue
		}
		keyword := strings.TrimSpace(row[colIdx["keyword"]])
		question := strings.TrimSpace(row[colIdx["question"]])
		answer := strings.TrimSpace(row[colIdx["answer"]])
		if keyword == "" || question == "" || answer == "" {
			skipped++
			continue
		}
		cat := "通用"
		if hasCat && catIdx < len(row) {
			if v := strings.TrimSpace(row[catIdx]); v != "" {
				cat = v
			}
		}
		entry := models.Entry{Keyword: keyword, Question: question, Answer: answer, Category: cat}
		if err := db.Create(&entry).Error; err != nil {
			skipped++
		} else {
			imported++
		}
	}
	return ImportResult{Imported: imported, Skipped: skipped}
}