package main

import (
	"errors"
	"fmt"
	"io/ioutil"
	"log"
	"net/mail"
	"regexp"
	"strings"

	"github.com/google/uuid"
)

type scraper interface {
	scrape(*mail.Message) ([]*Transaction, error)
}

type chaseScraper struct{}
type citiScraper struct{}

func Scrape(m *mail.Message) ([]*Transaction, error) {
	scraper, err := buildScraper(m)
	if err != nil {
		return nil, err
	}
	return scraper.scrape(m)
}

func buildScraper(m *mail.Message) (scraper, error) {
	subject := fmt.Sprint(m.Header["Subject"])
	if !containsAny(subject, "transaction", "report", "Transaction") {
		return nil, errors.New("cannot build scraper for subject " + subject)
	}
	log.Printf("%+v", m.Header)
	from := fmt.Sprint(m.Header["From"])
	if strings.Contains(from, "Chase") {
		return newChaseScraper(), nil
	}
	if strings.Contains(from, "Citi") {
		return newCitiScraper(), nil
	}
	return nil, errors.New("unknown sender: " + from)
}

func newChaseScraper() scraper {
	return &chaseScraper{}
}

func newCitiScraper() scraper {
	return &citiScraper{}
}

func containsAny(a string, b ...string) bool {
	for i := range b {
		if strings.Contains(a, b[i]) {
			return true
		}
	}
	return false
}

func (c *chaseScraper) scrape(m *mail.Message) ([]*Transaction, error) {
	b, err := ioutil.ReadAll(m.Body)
	if err != nil {
		return nil, err
	}
	regexp := regexp.MustCompile(`A charge of \([^)]*\) (?P<amount>[\d\.]+) at (?P<account>.*) has been authorized`)
	matches := regexp.FindSubmatch(b)
	if len(matches) < 2 {
		return nil, fmt.Errorf("no matches found: %+v: %s", matches, b)
	}
	results := make(map[string][]string)
	for i, name := range regexp.SubexpNames() {
		if i != 0 && name != "" {
			results[name] = append(results[name], string(matches[i]))
		}
	}
	if len(results) != 2 || len(results["amount"]) != len(results["account"]) {
		return nil, fmt.Errorf("unexpected matches found looking for transactions: %+v", results)
	}
	transactions := make([]*Transaction, len(results["amount"]))
	for i := range results["amount"] {
		transactions[i] = &Transaction{
			Amount:  results["amount"][i],
			Account: results["account"][i],
			Bank:    Chase,
			Date:    fmt.Sprint(m.Header["Date"]),
			ID:      uuid.New().String(), // TODO random based on date, amount, account, and bank so find dupes
		}
	}
	return transactions, nil
}

func (c *citiScraper) scrape(m *mail.Message) ([]*Transaction, error) {
	panic("not impl")
}