| 1 | package usage |
| 2 | |
| 3 | import ( |
| 4 | "context" |
| 5 | "encoding/json" |
| 6 | "errors" |
| 7 | "fmt" |
| 8 | "os" |
| 9 | "time" |
| 10 | |
| 11 | "github.com/carlosframework/platform/internal/release" |
| 12 | ) |
| 13 | |
| 14 | // Statement is usage/accounts/<acct>/<month>.json — one account's |
| 15 | // month-to-date totals per meter, the durable input a future billing engine |
| 16 | // consumes (statement × price sheet = invoice; spec: billing readiness). |
| 17 | // Meters is keyed by the Meter* vocabulary. CoveredDays/DaysInMonth carry |
| 18 | // the honesty label every rendered total must show. |
| 19 | type Statement struct { |
| 20 | V int `json:"v"` // 1 |
| 21 | Account string `json:"account"` |
| 22 | Month string `json:"month"` // "2006-01" |
| 23 | Meters map[string]float64 `json:"meters"` |
| 24 | CoveredDays int `json:"covered_days"` |
| 25 | DaysInMonth int `json:"days_in_month"` |
| 26 | UpdatedAt time.Time `json:"updated_at"` |
| 27 | } |
| 28 | |
| 29 | // StatementKey is the bucket key for an account's month statement. |
| 30 | func StatementKey(acct, month string) string { |
| 31 | return "usage/accounts/" + acct + "/" + month + ".json" |
| 32 | } |
| 33 | |
| 34 | // StatementsPrefix lists an account's statements. |
| 35 | func StatementsPrefix(acct string) string { return "usage/accounts/" + acct + "/" } |
| 36 | |
| 37 | // AccountsPrefix discovers accounts that have statements. |
| 38 | const AccountsPrefix = "usage/accounts/" |
| 39 | |
| 40 | // UpsertStatement CAS-replaces the account's month statement (3 attempts). |
| 41 | func UpsertStatement(ctx context.Context, s release.Store, st Statement) error { |
| 42 | key := StatementKey(st.Account, st.Month) |
| 43 | body, err := json.Marshal(st) |
| 44 | if err != nil { |
| 45 | return err |
| 46 | } |
| 47 | for attempt := 0; attempt < 3; attempt++ { |
| 48 | _, etag, err := s.Get(ctx, key) |
| 49 | if err != nil { |
| 50 | if !errors.Is(err, os.ErrNotExist) { |
| 51 | return err |
| 52 | } |
| 53 | etag = "" |
| 54 | } |
| 55 | if _, err := s.Put(ctx, key, body, etag); err == nil { |
| 56 | return nil |
| 57 | } else if !errors.Is(err, release.ErrCASConflict) { |
| 58 | return err |
| 59 | } |
| 60 | } |
| 61 | return fmt.Errorf("usage: %s: lost CAS race three times", key) |
| 62 | } |
| 63 | |
| 64 | // CreateDayObject writes key create-only. (false, nil) means another writer |
| 65 | // won today — the daily-pass idempotence rule (spec: error handling). |
| 66 | func CreateDayObject(ctx context.Context, s release.Store, key string, v any) (bool, error) { |
| 67 | body, err := json.Marshal(v) |
| 68 | if err != nil { |
| 69 | return false, err |
| 70 | } |
| 71 | if _, err := s.Put(ctx, key, body, ""); err != nil { |
| 72 | if errors.Is(err, release.ErrCASConflict) { |
| 73 | return false, nil |
| 74 | } |
| 75 | return false, err |
| 76 | } |
| 77 | return true, nil |
| 78 | } |
| 79 | |
amadan