package budget

import (
	"context"
	"sync"
	"time"
)

// Memory is a zero-dependency in-process BudgetStorage: per-user rolling-window
// usage held in memory (lost on restart). The default behind DBBudget for a
// light host or tests; mort uses its GORM Storage, contrib/store adds SQLite.
type Memory struct {
	mu   sync.Mutex
	rows map[string]*SkillBudget
}

// NewMemory returns an empty in-memory BudgetStorage.
func NewMemory() *Memory { return &Memory{rows: map[string]*SkillBudget{}} }

var _ BudgetStorage = (*Memory)(nil)

func (m *Memory) Initialize(context.Context) error { return nil }

func (m *Memory) Get(_ context.Context, userID string) (*SkillBudget, error) {
	m.mu.Lock()
	defer m.mu.Unlock()
	r, ok := m.rows[userID]
	if !ok {
		return nil, nil
	}
	cp := *r // copy out so callers can't mutate our row
	return &cp, nil
}

func (m *Memory) Add(_ context.Context, userID string, secondsUsed float64, now time.Time) error {
	m.mu.Lock()
	defer m.mu.Unlock()
	r, ok := m.rows[userID]
	if !ok {
		m.rows[userID] = &SkillBudget{
			UserID: userID, WindowStart: now,
			SecondsUsed: secondsUsed, RunsCount: 1, UpdatedAt: now,
		}
		return nil
	}
	// Roll the window over if it's older than the window length.
	if now.Sub(r.WindowStart) >= budgetWindow {
		r.WindowStart = now
		r.SecondsUsed = 0
		r.RunsCount = 0
	}
	r.SecondsUsed += secondsUsed
	r.RunsCount++
	r.UpdatedAt = now
	return nil
}