package postgres

import (
	"context"
	"encoding/csv"
	"fmt"
	"io"

	"github.com/google/uuid"
)

type YNABExport struct {
	queries  *Queries
	budgetID uuid.UUID
}

func NewYNABExport(context context.Context, queries *Queries, budgetID uuid.UUID) (*YNABExport, error) {
	return &YNABExport{
		queries:  queries,
		budgetID: budgetID,
	}, nil
}

// ImportAssignments expects a TSV-file as exported by YNAB in the following format:
// "Month"	"Category Group/Category"	"Category Group"	"Category"	"Budgeted"	"Activity"	"Available"
// "Apr 2019"	"Income: Next Month"	"Income"	"Next Month"	0,00€	0,00€	0,00€
//
// Activity and Available are not imported, since they are determined by the transactions and historic assignments.
func (ynab *YNABExport) ExportAssignments(context context.Context, w io.Writer) error {
	csv := csv.NewWriter(w)
	csv.Comma = '\t'

	assignments, err := ynab.queries.GetAllAssignments(context, ynab.budgetID)
	if err != nil {
		return fmt.Errorf("load assignments: %w", err)
	}

	count := 0
	for _, assignment := range assignments {
		row := []string{
			assignment.Date.Format("Jan 2006"),
			assignment.Group + ": " + assignment.Category,
			assignment.Group,
			assignment.Category,
			assignment.Amount.String() + "€",
			NewZeroNumeric().String() + "€",
			NewZeroNumeric().String() + "€",
		}

		err := csv.Write(row)
		if err != nil {
			return fmt.Errorf("write assignment: %w", err)
		}
		count++
	}
	csv.Flush()

	fmt.Printf("Exported %d assignments\n", count)

	return nil
}

// ImportTransactions expects a TSV-file as exported by YNAB in the following format:
// "Account"	"Flag"	"Date"	"Payee"	"Category Group/Category"	"Category Group"	"Category"	"Memo"	"Outflow"	"Inflow"	"Cleared"
// "Cash"	""	"11.12.2021"	"Transfer : Checking"	""	""	""	"Brought to bank"	500,00€	0,00€	"Cleared".
func (ynab *YNABExport) ExportTransactions(context context.Context, w io.Writer) error {
	csv := csv.NewWriter(w)
	csv.Comma = '\t'

	transactions, err := ynab.queries.GetAllTransactionsForBudget(context, ynab.budgetID)
	if err != nil {
		return fmt.Errorf("load transactions: %w", err)
	}

	header := []string{
		"Account",
		"Flag",
		"Date",
		"Payee",
		"Category Group/Category",
		"Category Group",
		"Category",
		"Memo",
		"Outflow",
		"Inflow",
		"Cleared",
	}

	err = csv.Write(header)
	if err != nil {
		return fmt.Errorf("write transaction: %w", err)
	}

	count := 0
	for _, transaction := range transactions {
		row := GetTransactionRow(transaction)

		err := csv.Write(row)
		if err != nil {
			return fmt.Errorf("write transaction: %w", err)
		}
		count++
	}

	csv.Flush()

	fmt.Printf("Exported %d transactions\n", count)

	return nil
}

func GetTransactionRow(transaction GetAllTransactionsForBudgetRow) []string {
	row := []string{
		transaction.Account,
		"", // Flag
		transaction.Date.Format("02.01.2006"),
		transaction.Payee,
	}

	if transaction.CategoryGroup != "" && transaction.Category != "" {
		row = append(row,
			transaction.CategoryGroup+" : "+transaction.Category,
			transaction.CategoryGroup,
			transaction.Category)
	} else {
		row = append(row, "", "", "")
	}

	row = append(row, transaction.Memo)

	if transaction.Amount.IsPositive() {
		row = append(row, NewZeroNumeric().String()+"€", transaction.Amount.String()+"€")
	} else {
		row = append(row, transaction.Amount.String()[1:]+"€", NewZeroNumeric().String()+"€")
	}

	return append(row, string(transaction.Status))
}