| 1 | // SPDX-License-Identifier: GPL-3.0-or-later |
| 2 | |
| 3 | package sqlquery |
| 4 | |
| 5 | import ( |
| 6 | "database/sql" |
| 7 | "fmt" |
| 8 | ) |
| 9 | |
| 10 | type ScanValueType string |
| 11 | |
| 12 | const ( |
| 13 | ScanValueString ScanValueType = "string" |
| 14 | ScanValueInteger ScanValueType = "integer" |
| 15 | ScanValueFloat ScanValueType = "float" |
| 16 | ScanValueDiscard ScanValueType = "discard" |
| 17 | ) |
| 18 | |
| 19 | // ScanColumnSpec describes how a query result column should be scanned and normalized. |
| 20 | type ScanColumnSpec struct { |
| 21 | Type ScanValueType |
| 22 | Transform func(any) any |
| 23 | } |
| 24 | |
| 25 | // RowScanner is the minimal interface required for typed row scanning. |
| 26 | type RowScanner interface { |
| 27 | Next() bool |
| 28 | Scan(dest ...any) error |
| 29 | } |
| 30 | |
| 31 | // ScanTypedRows scans all rows according to specs and returns normalized [][]any rows. |
| 32 | // The function intentionally does not call rows.Err(); callers keep control over that. |
| 33 | func ScanTypedRows(rows RowScanner, specs []ScanColumnSpec) ([][]any, error) { |
| 34 | data := make([][]any, 0, 500) |
| 35 | holders := makeScanHolders(specs) |
| 36 | |
| 37 | for rows.Next() { |
| 38 | if err := rows.Scan(holders.ptrs...); err != nil { |
| 39 | return nil, fmt.Errorf("scan row: %w", err) |
| 40 | } |
| 41 | |
| 42 | row := make([]any, len(specs)) |
| 43 | for i := range holders.ptrs { |
| 44 | value, ok := holders.value(i) |
| 45 | if ok && specs[i].Transform != nil { |
| 46 | value = specs[i].Transform(value) |
| 47 | } |
| 48 | row[i] = value |
| 49 | } |
| 50 | data = append(data, row) |
| 51 | } |
| 52 | |
| 53 | return data, nil |
| 54 | } |
| 55 | |
| 56 | type scanHolders struct { |
| 57 | ptrs []any |
| 58 | } |
| 59 | |
| 60 | func makeScanHolders(specs []ScanColumnSpec) scanHolders { |
| 61 | holders := scanHolders{ptrs: make([]any, len(specs))} |
| 62 | for i, spec := range specs { |
| 63 | switch spec.Type { |
| 64 | case ScanValueString: |
| 65 | holders.ptrs[i] = &sql.NullString{} |
| 66 | case ScanValueInteger: |
| 67 | holders.ptrs[i] = &sql.NullInt64{} |
| 68 | case ScanValueFloat: |
| 69 | holders.ptrs[i] = &sql.NullFloat64{} |
| 70 | case ScanValueDiscard: |
| 71 | holders.ptrs[i] = new(any) |
| 72 | default: |
| 73 | holders.ptrs[i] = &sql.NullString{} |
| 74 | } |
| 75 | } |
| 76 | return holders |
| 77 | } |
| 78 | |
| 79 | func (h scanHolders) value(i int) (any, bool) { |
| 80 | switch v := h.ptrs[i].(type) { |
| 81 | case *sql.NullString: |
| 82 | if v.Valid { |
| 83 | return v.String, true |
| 84 | } |
| 85 | return "", false |
| 86 | case *sql.NullInt64: |
| 87 | if v.Valid { |
| 88 | return v.Int64, true |
| 89 | } |
| 90 | return int64(0), false |
| 91 | case *sql.NullFloat64: |
| 92 | if v.Valid { |
| 93 | return v.Float64, true |
| 94 | } |
| 95 | return float64(0), false |
| 96 | case *any: |
| 97 | return nil, false |
| 98 | default: |
| 99 | return nil, false |
| 100 | } |
| 101 | } |