package parser

import (
	"encoding/csv"
	"fmt"
	"io"
	"math"
	"strconv"
	"strings"
	"time"

	"financeiro-carvalho/internal/model"
)

func ParseCSV(r io.Reader, m model.CSVMapping) ([]model.ImportRow, []string) {
	if m.DateFormat == "" {
		m.DateFormat = "02/01/2006"
	}
	if m.DecimalSeparator == "" {
		m.DecimalSeparator = ","
	}
	fieldSep := ','
	if m.FieldSeparator == ";" {
		fieldSep = ';'
	}

	reader := csv.NewReader(r)
	reader.Comma = fieldSep
	reader.LazyQuotes = true
	reader.TrimLeadingSpace = true

	var rows []model.ImportRow
	var errs []string
	lineNum := 0

	for {
		record, err := reader.Read()
		if err == io.EOF {
			break
		}
		lineNum++
		if err != nil {
			errs = append(errs, fmt.Sprintf("linha %d: %v", lineNum, err))
			continue
		}
		if lineNum == 1 && m.HasHeader {
			continue
		}

		maxCol := max3(m.DateColumn, m.AmountColumn, m.DescriptionColumn)
		if len(record) <= maxCol {
			errs = append(errs, fmt.Sprintf("linha %d: colunas insuficientes (%d)", lineNum, len(record)))
			continue
		}

		dateStr := strings.TrimSpace(record[m.DateColumn])
		amtStr := strings.TrimSpace(record[m.AmountColumn])
		desc := cleanDescription(record[m.DescriptionColumn])

		// Skip blank rows (e.g. empty line after header in some bank exports)
		if dateStr == "" && amtStr == "" && desc == "" {
			continue
		}

		t, err := time.Parse(m.DateFormat, dateStr)
		if err != nil {
			errs = append(errs, fmt.Sprintf("linha %d: data inválida %q", lineNum, dateStr))
			continue
		}

		// Strip currency symbols (R$, $, €, etc.) keeping digits, comma, dot, minus
		cleaned := strings.Map(func(r rune) rune {
			if r >= '0' && r <= '9' || r == ',' || r == '.' || r == '-' {
				return r
			}
			return -1
		}, amtStr)
		cleaned = strings.TrimSpace(cleaned)

		if m.DecimalSeparator == "," {
			cleaned = strings.ReplaceAll(cleaned, ".", "")
			cleaned = strings.ReplaceAll(cleaned, ",", ".")
		}
		amt, err := strconv.ParseFloat(cleaned, 64)
		if err != nil || cleaned == "" {
			errs = append(errs, fmt.Sprintf("linha %d: valor inválido %q", lineNum, amtStr))
			continue
		}

		if m.SkipNegative && amt < 0 {
			continue
		}

		txType := "expense"
		if !m.AllExpenses && amt > 0 {
			txType = "income"
		}

		rows = append(rows, model.ImportRow{
			Date:        t.Format("2006-01-02"),
			Amount:      math.Abs(amt),
			Description: desc,
			Type:        txType,
		})
	}
	return rows, errs
}

func max3(a, b, c int) int {
	if b > a {
		a = b
	}
	if c > a {
		a = c
	}
	return a
}