package fetch

import (
	"fmt"
	"sync/atomic"
)

// counters accumulates transfer activity for one repository's summary log
// line. Counters are atomic because download workers run concurrently.
type counters struct {
	Fetched      atomic.Int64
	FetchedBytes atomic.Int64
	Unchanged    atomic.Int64
	Pruned       atomic.Int64
	Planned      atomic.Int64
	PlannedBytes atomic.Int64
}

// Stats collects transfer activity for the repository currently
// synchronizing. The CLI synchronizes repositories sequentially, so one
// package-level collector suffices there. The server's concurrent crawls
// interleave into these counters, so their values are only meaningful in
// the sequential path; the server must not report them.
var Stats = &counters{}

// Reset clears the collector for the next repository.
func (s *counters) Reset() {
	s.Fetched.Store(0)
	s.FetchedBytes.Store(0)
	s.Unchanged.Store(0)
	s.Pruned.Store(0)
	s.Planned.Store(0)
	s.PlannedBytes.Store(0)
}

// FormatBytes renders a byte count in a human readable unit.
func FormatBytes(n int64) string {
	const unit = 1024
	const prefixes = "KMGTPE"
	if n < unit {
		return fmt.Sprintf("%d B", n)
	}
	div, exp := int64(unit), 0
	// Cap the exponent at the last available prefix so an unexpectedly
	// large count can never index past the prefix table.
	for m := n / unit; m >= unit && exp < len(prefixes)-1; m /= unit {
		div *= unit
		exp++
	}
	return fmt.Sprintf("%.1f %ciB", float64(n)/float64(div), prefixes[exp])
}