package main

import (
	"errors"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
	"strconv"
	"strings"
)

func readQuota(root string) int64 {
	b, err := os.ReadFile(filepath.Join(root, "quota"))
	if err != nil {
		return 0
	}
	n, _ := parseSize(strings.TrimSpace(string(b)))
	return n
}

func parseSize(s string) (int64, error) {
	s = strings.ToUpper(strings.TrimSpace(s))
	s = strings.TrimSpace(strings.TrimSuffix(strings.TrimSuffix(s, "B"), "I"))
	mult := int64(1)
	switch {
	case strings.HasSuffix(s, "G"):
		mult, s = 1<<30, strings.TrimSuffix(s, "G")
	case strings.HasSuffix(s, "M"):
		mult, s = 1<<20, strings.TrimSuffix(s, "M")
	case strings.HasSuffix(s, "K"):
		mult, s = 1<<10, strings.TrimSuffix(s, "K")
	}
	n, err := strconv.ParseInt(strings.TrimSpace(s), 10, 64)
	if err != nil || n < 0 {
		return 0, errors.New("size must be a number with an optional K, M or G suffix")
	}
	return n * mult, nil
}

func usage(dir string) int64 {
	var total int64
	filepath.WalkDir(dir, func(p string, d fs.DirEntry, err error) error {
		if err == nil && !d.IsDir() {
			if info, err := d.Info(); err == nil {
				total += info.Size()
			}
		}
		return nil
	})
	return total
}

func overQuota(root string, owner string) (bool, int64, int64) {
	quota := readQuota(root)
	if quota == 0 {
		return false, 0, 0
	}
	used := usage(filepath.Join(root, "repos", owner))
	return used >= quota, used, quota
}

func quotaMessage(used, quota int64) string {
	return fmt.Sprintf("disk quota exceeded, %s used of %s", humanSize(used), humanSize(quota))
}

func writeQuota(root string, n int64) error {
	return os.WriteFile(filepath.Join(root, "quota"), []byte(strconv.FormatInt(n, 10)+"\n"), 0o644)
}

func pushLimit(root, owner string) []string {
	if over, used, quota := overQuota(root, owner); quota > 0 && !over {
		return []string{"-c", "receive.maxInputSize=" + strconv.FormatInt(quota-used, 10)}
	}
	return nil
}

func compactSize(n int64) string {
	for _, u := range []struct {
		suffix string
		size   int64
	}{{"G", 1 << 30}, {"M", 1 << 20}, {"K", 1 << 10}} {
		if n >= u.size && n%u.size == 0 {
			return strconv.FormatInt(n/u.size, 10) + u.suffix
		}
	}
	return strconv.FormatInt(n, 10)
}