package ledger

import (
	"bufio"
	"bytes"
	"io"
	"os"
	"strconv"
)

type BPIs map[Currency]BPI

type BPI map[string]float64

func NewBPIs(p string) (BPIs, error) {
	f, err := os.Open(p)
	if os.IsNotExist(err) {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	defer f.Close()

	result := make(map[Currency]BPI)

	r := bufio.NewReader(f)
	for {
		line, err := readTransactionLine(r)
		if len(line) > 0 {
			fields := bytes.Fields(line)
			if len(fields) > 3 {
				date := string(fields[1])
				currency := Currency(fields[len(fields)-2])
				value, err := strconv.ParseFloat(string(fields[len(fields)-1][1:]), 64)
				if err != nil {
					return nil, err
				}
				if _, ok := result[currency]; !ok {
					result[currency] = make(BPI)
				}
				result[currency][date] = value
			}
		}
		if err == io.EOF {
			return result, nil
		} else if err != nil {
			return result, err
		}
	}
}

func (bpi BPI) Lookup(date string) float64 {
	var closestWithoutGoingOver string
	for k := range bpi {
		if k <= date && k > closestWithoutGoingOver {
			closestWithoutGoingOver = k
		}
	}
	if closestWithoutGoingOver == "" {
		return 0
	}
	return bpi[closestWithoutGoingOver]
}