package main

import (
	"bytes"
	"errors"
	"fmt"
	"io/ioutil"
	"net/mail"
	"regexp"
	"strconv"
	"strings"
)

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

type fidelityScraper struct{}
type bankOfAmericaScraper struct{}
type chaseScraper struct{}
type citiScraper struct{}
type uccuScraper struct{}

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

func buildScraper(m *mail.Message, banks map[Bank]bool) (scraper, error) {
	subject := fmt.Sprint(m.Header["Subject"])
	if !containsAny(subject, "transaction", "report", "Transaction", "payment", "Payment", "Deposit", "Withdrawal") {
		return nil, errors.New("cannot build scraper for subject " + subject)
	}
	from := fmt.Sprint(m.Header["From"])
	if strings.Contains(from, "Chase") && banks[Chase] {
		return newChaseScraper(), nil
	}
	if strings.Contains(from, "Fidelity") && banks[Fidelity] {
		return newFidelityScraper(), nil
	}
	if strings.Contains(from, "Bank of America") && banks[BankOfAmerica] {
		return newBankOfAmericaScraper(), nil
	}
	if strings.Contains(from, "Citi") && banks[Citi] {
		return newCitiScraper(), nil
	}
	if strings.Contains(from, "Notifications@uccu.com") && banks[UCCU] {
		return newUCCUScraper(), nil
	}
	return nil, errors.New("unknown sender: " + from)
}

func newFidelityScraper() scraper {
	return &fidelityScraper{}
}

func newBankOfAmericaScraper() scraper {
	return &bankOfAmericaScraper{}
}

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

func newUCCUScraper() scraper {
	return &uccuScraper{}
}

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) {
	if transactions, err := c.scrape2025Balance(m); err == nil && len(transactions) > 0 {
		return transactions, err
	}
	if transactions, err := c.scrape2021(m); err == nil && len(transactions) > 0 {
		return transactions, err
	}
	return c.scrape2020(m)
}

func (c *chaseScraper) scrape2025Balance(m *mail.Message) ([]*Transaction, error) {
	re := regexp.MustCompile(`^Your.*balance is \$[0-9,\.]*$`)
	if !re.Match([]byte(m.Header["Subject"][0])) {
		return nil, errors.New("no match subject search")
	}
	subject := m.Header["Subject"][0]

	fields := strings.Fields(subject)
	amount := fields[len(fields)-1]
	amount = strings.TrimLeft(amount, "$")
	amount = strings.ReplaceAll(amount, ",", "")

	b, err := ioutil.ReadAll(m.Body)
	if err != nil {
		return nil, err
	}

	re = regexp.MustCompile(`>Chase = [^<]*`)
	account := strings.TrimPrefix(string(re.Find(b)), ">Chase = ")

	return []*Transaction{NewTransaction(account, amount, "*", fmt.Sprint(m.Header["Date"]), Chase)}, nil
}

func (c *chaseScraper) scrape2021(m *mail.Message) ([]*Transaction, error) {
	if t, err := c.scrape2021Payment(m); err == nil {
		return t, err
	}
	return c.scrape2021Charge(m)
}

func (c *chaseScraper) scrape2021Payment(m *mail.Message) ([]*Transaction, error) {
	re := regexp.MustCompile(`^We've received your .* payment$`)
	if !re.Match([]byte(m.Header["Subject"][0])) {
		return nil, errors.New("no match subject search")
	}

	b, err := ioutil.ReadAll(m.Body)
	if err != nil {
		return nil, err
	}

	re = regexp.MustCompile(`\$[0-9,]+\.[0-9]{2}`)
	amount := "-" + strings.TrimLeft(string(re.Find(b)), "$")
	amount = strings.TrimLeft(string(re.Find(b)), "$")
	amount = strings.ReplaceAll(amount, ",", "")

	vendor := "Payment"

	re = regexp.MustCompile(`\(\.\.\.[0-9]{4}\)`)
	match := re.Find(b)
	re = regexp.MustCompile(`[0-9]{4}`)
	account := string(re.Find(match))

	return []*Transaction{NewTransaction(account, amount, vendor, fmt.Sprint(m.Header["Date"]), Chase)}, nil
}

func (c *chaseScraper) scrape2021Charge(m *mail.Message) ([]*Transaction, error) {
	re := regexp.MustCompile(`^Your \$(?P<amount>[,0-9\.]*) transaction with (?P<vendor>.*)$`)
	matches := re.FindSubmatch([]byte(m.Header["Subject"][0]))
	if len(matches) < 1 {
		return nil, errors.New("no match subject search")
	}
	amount := string(matches[1])
	amount = strings.ReplaceAll(amount, ",", "")
	vendor := string(matches[2])

	b, _ := ioutil.ReadAll(m.Body)
	re = regexp.MustCompile(`\(\.\.\.[0-9]{4}\)`)
	match := re.Find(b)
	re = regexp.MustCompile(`[0-9]{4}`)
	account := string(re.Find(match))

	return []*Transaction{NewTransaction(account, amount, vendor, fmt.Sprint(m.Header["Date"]), Chase)}, nil
}

func (c *chaseScraper) scrape2020(m *mail.Message) ([]*Transaction, error) {
	b, err := ioutil.ReadAll(m.Body)
	if err != nil {
		return nil, err
	}
	re := regexp.MustCompile(`A charge of \([^)]*\) (?P<amount>[\d\.]+) at (?P<vendor>.*) has been authorized`)
	matches := re.FindSubmatch(b)
	if len(matches) < 2 {
		return nil, fmt.Errorf("no full matches found")
	}
	results := make(map[string][]string)
	for i, name := range re.SubexpNames() {
		if i != 0 && name != "" {
			results[name] = append(results[name], string(matches[i]))
		}
	}
	if len(results) != 2 || len(results["amount"]) != len(results["vendor"]) {
		return nil, fmt.Errorf("unexpected matches found looking for transactions: %+v", results)
	}
	re = regexp.MustCompile(`account ending in (?P<account>[0-9]{4})\.`)
	match := re.Find(b)
	re = regexp.MustCompile(`[0-9]{4}`)
	account := string(re.Find(match))
	transactions := make([]*Transaction, len(results["amount"]))
	for i := range results["amount"] {
		transactions[i] = NewTransaction(account, results["amount"][i], results["vendor"][i], fmt.Sprint(m.Header["Date"]), Chase)
	}
	return transactions, nil
}

func (c *citiScraper) scrape(m *mail.Message) ([]*Transaction, error) {
	date := fmt.Sprint(m.Header["Date"])
	b, err := ioutil.ReadAll(m.Body)
	if err != nil {
		return nil, err
	}
	re := regexp.MustCompile(`Citi Alert: A \$[,0-9][,0-9]*\.[0-9][0-9] transaction was made at .* on card ending in`)
	match := re.Find(b)
	if len(match) == 0 {
		return nil, nil
	}

	rePrice := regexp.MustCompile(`[0-9][0-9,]*\.[0-9][0-9]`)
	price := rePrice.Find(match)
	price = []byte(strings.ReplaceAll(string(price), ",", ""))

	vendor := bytes.Split(bytes.Split(match, []byte(" on card ending in"))[0], []byte("transaction was made at "))[1]

	transaction := NewTransaction(Citi.String(), string(price), string(vendor), date, Citi)

	return []*Transaction{transaction}, nil
}

func (c *uccuScraper) scrape(m *mail.Message) ([]*Transaction, error) {
	b, err := ioutil.ReadAll(m.Body)
	if err != nil {
		return nil, err
	}
	regexp := regexp.MustCompile(`\$([0-9]+,?)+\.[0-9][0-9]`)
	match := regexp.Find(b)
	if len(match) == 0 {
		return nil, fmt.Errorf("no matches found")
	}
	match = match[1:]
	match = bytes.ReplaceAll(match, []byte(","), []byte{})
	f, err := strconv.ParseFloat(string(match), 10)
	if err != nil {
		return nil, err
	}
	if !bytes.Contains(b, []byte("credit")) {
		f *= -1.0
	}
	transaction := NewTransaction(UCCU.String(), fmt.Sprintf("%.2f", f), "?", fmt.Sprint(m.Header["Date"]), UCCU)
	return []*Transaction{transaction}, nil
}

func (c *fidelityScraper) scrape(m *mail.Message) ([]*Transaction, error) {
	subject := fmt.Sprint(m.Header["Subject"])
	if strings.Contains(subject, "Debit Withdrawal") {
		return c.scrapeWithdrawal(m)
	}
	if strings.Contains(subject, "Deposit Received") {
		return c.scrapeDeposit(m)
	}
	panic(nil)
}

func (c *fidelityScraper) scrapeDeposit(m *mail.Message) ([]*Transaction, error) {
	b, err := ioutil.ReadAll(m.Body)
	if err != nil {
		return nil, err
	}

	fidelAcc, _ := findSubstringBetween(b, "Account: XXXXX", "\n")

	transaction := NewTransaction(
		fmt.Sprintf("%s-%s", Fidelity, fidelAcc),
		"?.??",
		"misc",
		fmt.Sprint(m.Header["Date"]),
		Fidelity,
	)
	return []*Transaction{transaction}, nil
}

func (c *fidelityScraper) scrapeWithdrawal(m *mail.Message) ([]*Transaction, error) {
	b, err := ioutil.ReadAll(m.Body)
	if err != nil {
		return nil, err
	}

	amount, amountOk := findSubstringBetween(b, "in the amount of $", " ")
	fidelAcc, fidelAccOk := findSubstringBetween(b, "For account ending in ", ":")
	acc, accOk := findSubstringBetween(b, "in the amount of $"+amount+" by ", ".")

	if amount == "" || acc == "" {
		return nil, fmt.Errorf("no amount/account found: fidelAcc=%v,fidelAccOk=%v, acc=%v,accOk=%v, amount=%v,amountOk=%v", fidelAcc, fidelAccOk, acc, accOk, amount, amountOk)
	}
	transaction := NewTransaction(fmt.Sprintf("%s-%s", Fidelity, fidelAcc), amount, acc, fmt.Sprint(m.Header["Date"]), Fidelity)
	return []*Transaction{transaction}, nil
}

func (c *bankOfAmericaScraper) scrape(m *mail.Message) ([]*Transaction, error) {
	subject := fmt.Sprint(m.Header["Subject"])
	if strings.Contains(subject, "Credit card transaction") {
		return c.scrapeCharge(m)
	}
	if strings.Contains(subject, "Credit Card Payment") {
		return c.scrapePayment(m)
	}
	return nil, errors.New("not impl")
}

func (c *bankOfAmericaScraper) scrapeCharge(m *mail.Message) ([]*Transaction, error) {
	b, err := ioutil.ReadAll(m.Body)
	if err != nil {
		return nil, err
	}
	if v, err := c.scrapeCharge2023(m, b); err == nil {
		return v, nil
	}
	return c.scrapeCharge2024(m, b)
}

func (c *bankOfAmericaScraper) scrapeCharge2023(m *mail.Message, b []byte) ([]*Transaction, error) {
	amount := findFloatAfter(b, "Amount: $")
	acc := string(findLineAfter(b, "Where: "))

	if amount == "" || acc == "" {
		return nil, errors.New("no amount/account found")
	}
	transaction := NewTransaction(BankOfAmerica.String(), amount, acc, fmt.Sprint(m.Header["Date"]), BankOfAmerica)
	return []*Transaction{transaction}, nil
}

func (c *bankOfAmericaScraper) scrapeCharge2024(m *mail.Message, b []byte) ([]*Transaction, error) {
	amountPattern := `Amount:[^\$]*\$([0-9]*\.[0-9]*)`
	amountMatches := regexp.MustCompile(amountPattern).FindSubmatch(bytes.ReplaceAll(b, []byte("\n"), []byte(" ")))
	if len(amountMatches) < 2 {
		return nil, fmt.Errorf("email does not match amount %q: %+v", amountPattern, amountMatches)
	}
	amount := string(amountMatches[1])

	b2 := bytes.Split(b, []byte("Where:"))[1]
	b3 := bytes.Split(b2, []byte("</tr>"))[0]
	b4 := bytes.ReplaceAll(b3, []byte("\n"), []byte(" "))
	accPattern := `<b>(.*)</b>`
	accMatches := regexp.MustCompile(accPattern).FindSubmatch(b4)
	if len(accMatches) < 2 {
		return nil, fmt.Errorf("email does not match acc %q", accPattern)
	}
	acc := string(accMatches[1])

	if amount == "" || acc == "" {
		return nil, errors.New("no amount/account found")
	}
	transaction := NewTransaction(BankOfAmerica.String(), amount, acc, fmt.Sprint(m.Header["Date"]), BankOfAmerica)
	return []*Transaction{transaction}, nil
}

func (c *bankOfAmericaScraper) scrapePayment(m *mail.Message) ([]*Transaction, error) {
	b, err := ioutil.ReadAll(m.Body)
	if err != nil {
		return nil, err
	}
	amount := "-" + findFloatAfter(b, "Payment: $")
	acc := "Payment"
	if amount == "" || acc == "" {
		return nil, errors.New("no amount/account found")
	}
	transaction := NewTransaction(BankOfAmerica.String(), amount, acc, fmt.Sprint(m.Header["Date"]), BankOfAmerica)
	return []*Transaction{transaction}, nil
}

func findSubstringBetween(b []byte, prefix, suffix string) (string, bool) {
	byPre := bytes.Split(b, []byte(prefix))
	if len(byPre) < 2 {
		return "", false
	}
	bySuff := bytes.Split(byPre[1], []byte(suffix))
	if len(bySuff) < 2 {
		return "", false
	}
	return string(bySuff[0]), true
}

func findFloatAfter(b []byte, prefix string) string {
	amount := string(findLineAfter(b, prefix))
	words := strings.Split(amount, " ")
	lastword := words[len(words)-1]
	escapedfloat := strings.TrimPrefix(lastword, "$")
	fixEscape := strings.ReplaceAll(escapedfloat, "=2E", ".")
	amount = fixEscape
	return amount
}

func findLineAfter(b []byte, prefix string) []byte {
	for _, line := range bytes.Split(b, []byte("\n")) {
		if bytes.HasPrefix(line, []byte(prefix)) {
			return bytes.TrimSpace(bytes.TrimPrefix(line, []byte(prefix)))
		}
	}
	return nil
}