package membership

import (
	"context"
	"errors"
	"fuj-management/go/internal/domain/reconcile"
)

// ErrIOPending is returned by stub loader methods until the M4 IO layer lands.
var ErrIOPending = errors.New("io layer not yet wired up; lands in milestone M4 (sheets/drive/fio)")

// AttendanceLoader loads attendance and computed fees from the attendance Google Sheet.
type AttendanceLoader interface {
	LoadAdults(ctx context.Context) (members []reconcile.Member, sortedMonths []string, err error)
	LoadJuniors(ctx context.Context) (members []reconcile.Member, sortedMonths []string, err error)
}

// TransactionLoader loads payment rows from the payments Google Sheet.
type TransactionLoader interface {
	LoadTransactions(ctx context.Context) ([]reconcile.Transaction, error)
}

// ExceptionLoader loads manual fee overrides from the exceptions sheet tab.
type ExceptionLoader interface {
	LoadExceptions(ctx context.Context) (map[reconcile.ExceptionKey]reconcile.Exception, error)
}

// CacheFlusher can invalidate all cached data.
type CacheFlusher interface {
	FlushCache() (int, error)
}

// Sources is the aggregate interface required by ReconcileReport.
type Sources interface {
	AttendanceLoader
	TransactionLoader
	ExceptionLoader
	CacheFlusher
}

// NewStubSources returns a Sources whose every method returns ErrIOPending.
func NewStubSources() Sources { return stubSources{} }

type stubSources struct{}

func (stubSources) LoadAdults(_ context.Context) ([]reconcile.Member, []string, error) {
	return nil, nil, ErrIOPending
}

func (stubSources) LoadJuniors(_ context.Context) ([]reconcile.Member, []string, error) {
	return nil, nil, ErrIOPending
}

func (stubSources) LoadTransactions(_ context.Context) ([]reconcile.Transaction, error) {
	return nil, ErrIOPending
}

func (stubSources) LoadExceptions(_ context.Context) (map[reconcile.ExceptionKey]reconcile.Exception, error) {
	return nil, ErrIOPending
}

func (stubSources) FlushCache() (int, error) { return 0, nil }