fold package internal into package oblast

1 files changed, 294 insertions, 0 deletions

diff --git a/plan.go b/plan.go
new file mode 100644
index 0000000..da9f9b5
--- /dev/null
+++ b/plan.go
@@ -0,0 +1,294 @@
+// SPDX-FileCopyrightText: 2026 Stefan Majewsky <majewsky@gmx.net>
+// SPDX-License-Identifier: Apache-2.0
+
+package oblast
+
+import (
+	"errors"
+	"fmt"
+	"reflect"
+	"slices"
+	"strings"
+)
+
+// plan holds all information that we can derive from reflecting on a given type.
+// The queries held within are only valid within the context of a given SQL dialect.
+type plan struct {
+	TypeName              string   // for use in error messages
+	TableName             string   // from info.TableNameIs marker (if any)
+	AllColumnNames        []string // in order of struct fields
+	PrimaryKeyColumnNames []string // from info.PrimaryKeyIs marker (if any)
+	AutoColumnNames       []string // subset of AllColumnNames where field has `,auto` marker
+
+	// Argument for reflect.Value.FieldByIndex() for each column name.
+	IndexByColumnName map[string][]int
+
+	// In dialects with UsesLastInsertID() == true, whether the ID column must be written with reflect.Value.SetInt() or reflect.Value.SetUint().
+	FillIDWithSetUint bool
+	FillIDWithSetInt  bool
+
+	// Planned queries.
+	Select plannedQuery // only `SELECT ... FROM ... WHERE `; user supplies the rest during Select{,One}Where()
+	Insert plannedQuery
+	Update plannedQuery
+	Delete plannedQuery
+}
+
+// plannedQuery appears in type plan.
+type plannedQuery struct {
+	// Empty if the respective query type is not supported by this plan for lack of the required marker types.
+	Query string
+	// Arguments for reflect.Value.FieldByIndex() in the correct order for the query arguments of the above query.
+	ArgumentIndexes [][]int
+	// Arguments for reflect.Value.FieldByIndex() in the correct order for the Scan() arguments of the above query.
+	ScanIndexes [][]int
+}
+
+// planOpts holds additional arguments to buildPlan().
+type planOpts struct {
+	TableName             string
+	PrimaryKeyColumnNames []string
+}
+
+// buildPlan creates a new plan for the given struct type.
+func buildPlan(t reflect.Type, dialect Dialect, opts planOpts) (plan, error) {
+	if t.Kind() != reflect.Struct {
+		return plan{}, fmt.Errorf("expected struct type, but got kind %s", t.Kind().String())
+	}
+
+	var p = plan{
+		TypeName:              t.Name(),
+		TableName:             opts.TableName,
+		PrimaryKeyColumnNames: opts.PrimaryKeyColumnNames,
+		IndexByColumnName:     make(map[string][]int),
+	}
+
+	// discover addressable fields in this type,
+	// collect information from markers and tags
+	for _, field := range reflect.VisibleFields(t) {
+		tags := strings.Split(strings.TrimSpace(field.Tag.Get("db")), ",")
+
+		switch {
+		case field.PkgPath != "":
+			// ignore unexported fields (otherwise reflect.Value.Interface() on the field would panic)
+			continue
+		case field.Anonymous && field.Type.Kind() == reflect.Struct:
+			// for embedded struct fields, only consider their members, not the type itself, as a potential column
+			continue
+		default:
+			columnName, extraTags := tags[0], tags[1:]
+			if columnName == "-" {
+				continue
+			}
+			if columnName == "" {
+				columnName = field.Name
+			}
+			if otherIndex := p.IndexByColumnName[columnName]; otherIndex != nil {
+				return plan{}, fmt.Errorf(
+					"duplicate tag `db:%q` on field index %v, but also on field index %v",
+					columnName, otherIndex, field.Index,
+				)
+			}
+			p.IndexByColumnName[columnName] = field.Index
+			p.AllColumnNames = append(p.AllColumnNames, columnName)
+
+			for _, tag := range extraTags {
+				switch tag {
+				case "auto":
+					p.AutoColumnNames = append(p.AutoColumnNames, columnName)
+				default:
+					return plan{}, fmt.Errorf("unknown tag `db:%q` on field index %v", ","+tag, field.Index)
+				}
+			}
+		}
+	}
+
+	// validation: defining a primary key only makes sense for records that map onto a single table
+	if len(p.PrimaryKeyColumnNames) > 0 && p.TableName == "" {
+		return plan{}, errors.New("cannot declare a primary key without also providing the TableNameIs option")
+	}
+
+	// validation: oblast.PrimaryKeyInfo must refer to columns that exist
+	for _, columnName := range p.PrimaryKeyColumnNames {
+		_, ok := p.IndexByColumnName[columnName]
+		if !ok {
+			return plan{}, fmt.Errorf("no field has tag `db:%q`, but a field of this name was declared in the primary key", columnName)
+		}
+	}
+
+	// validation: LastInsertID() only works if at most one column is auto-filled, and if that column holds an integer type
+	if dialect.UsesLastInsertID() {
+		switch len(p.AutoColumnNames) {
+		case 0:
+			// nothing to check
+		case 1:
+			columnName := p.AutoColumnNames[0]
+			field := t.FieldByIndex(p.IndexByColumnName[columnName])
+			switch field.Type.Kind() { //nolint:exhaustive // false positive
+			case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+				p.FillIDWithSetInt = true
+			case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64:
+				p.FillIDWithSetUint = true
+			default:
+				return plan{}, fmt.Errorf(
+					"column is marked as auto-filled (%s), but this SQL dialect only supports auto-filling struct fields with integer types",
+					strings.Join(p.AutoColumnNames, ", "),
+				)
+			}
+		default:
+			return plan{}, fmt.Errorf(
+				"multiple columns are marked as auto-filled (%s), but this SQL dialect only supports at most one per table",
+				strings.Join(p.AutoColumnNames, ", "),
+			)
+		}
+	}
+
+	// prepare query strings
+	p.Select = p.buildSelectQueryIfPossible(dialect)
+	p.Insert = p.buildInsertQueryIfPossible(dialect)
+	p.Update = p.buildUpdateQueryIfPossible(dialect)
+	p.Delete = p.buildDeleteQueryIfPossible(dialect)
+
+	return p, nil
+}
+
+func (p plan) getNonAutoColumnNames() []string {
+	result := make([]string, 0, len(p.AllColumnNames)-len(p.AutoColumnNames))
+	for _, columnName := range p.AllColumnNames {
+		if !slices.Contains(p.AutoColumnNames, columnName) {
+			result = append(result, columnName)
+		}
+	}
+	return result
+}
+
+func (p plan) getNonPrimaryKeyColumnNames() []string {
+	result := make([]string, 0, len(p.AllColumnNames)-len(p.PrimaryKeyColumnNames))
+	for _, columnName := range p.AllColumnNames {
+		if !slices.Contains(p.PrimaryKeyColumnNames, columnName) {
+			result = append(result, columnName)
+		}
+	}
+	return result
+}
+
+func (p plan) buildSelectQueryIfPossible(dialect Dialect) plannedQuery {
+	if p.TableName == "" {
+		return plannedQuery{Query: ""}
+	}
+
+	var (
+		scanIndexes       = make([][]int, len(p.AllColumnNames))
+		quotedColumnNames = make([]string, len(p.AllColumnNames))
+	)
+	for idx, columnName := range p.AllColumnNames {
+		scanIndexes[idx] = p.IndexByColumnName[columnName]
+		quotedColumnNames[idx] = dialect.QuoteIdentifier(columnName)
+	}
+
+	query := fmt.Sprintf(
+		`SELECT %s FROM %s WHERE `,
+		strings.Join(quotedColumnNames, ", "),
+		dialect.QuoteIdentifier(p.TableName),
+	)
+	return plannedQuery{query, nil, scanIndexes}
+}
+
+func (p plan) buildInsertQueryIfPossible(dialect Dialect) plannedQuery {
+	if p.TableName == "" || len(p.AllColumnNames) == 0 {
+		return plannedQuery{Query: ""}
+	}
+	nonAutoColumnNames := p.getNonAutoColumnNames()
+	if len(nonAutoColumnNames) == 0 {
+		return plannedQuery{Query: ""}
+	}
+
+	var (
+		argumentIndexes    = make([][]int, len(nonAutoColumnNames))
+		scanIndexes        [][]int
+		quotedColumnNames  = make([]string, len(nonAutoColumnNames))
+		quotedPlaceholders = make([]string, len(nonAutoColumnNames))
+	)
+	for idx, columnName := range nonAutoColumnNames {
+		argumentIndexes[idx] = p.IndexByColumnName[columnName]
+		quotedColumnNames[idx] = dialect.QuoteIdentifier(columnName)
+		quotedPlaceholders[idx] = dialect.Placeholder(idx)
+	}
+	if len(p.AutoColumnNames) > 0 {
+		// NOTE: This is filled even if dialect.UsesLastInsertID() is false.
+		// We need this index to find the right value on which to run SetInt() or SetUint().
+		scanIndexes = make([][]int, len(p.AutoColumnNames))
+		for idx, columnName := range p.AutoColumnNames {
+			scanIndexes[idx] = p.IndexByColumnName[columnName]
+		}
+	}
+
+	query := fmt.Sprintf(
+		`INSERT INTO %s (%s) VALUES (%s)`,
+		dialect.QuoteIdentifier(p.TableName),
+		strings.Join(quotedColumnNames, ", "),
+		strings.Join(quotedPlaceholders, ", "),
+	)
+	if len(p.AutoColumnNames) > 0 {
+		query += dialect.InsertSuffixForAutoColumns(p.AutoColumnNames)
+	}
+	return plannedQuery{query, argumentIndexes, scanIndexes}
+}
+
+func (p plan) buildUpdateQueryIfPossible(dialect Dialect) plannedQuery {
+	if p.TableName == "" || len(p.PrimaryKeyColumnNames) == 0 {
+		return plannedQuery{Query: ""}
+	}
+	nonPrimaryKeyColumnNames := p.getNonPrimaryKeyColumnNames()
+	if len(nonPrimaryKeyColumnNames) == 0 {
+		return plannedQuery{Query: ""}
+	}
+
+	var (
+		setArgumentIndexes = make([][]int, len(nonPrimaryKeyColumnNames))
+		setClauses         = make([]string, len(nonPrimaryKeyColumnNames))
+	)
+	for idx, columnName := range nonPrimaryKeyColumnNames {
+		setArgumentIndexes[idx] = p.IndexByColumnName[columnName]
+		setClauses[idx] = fmt.Sprintf("%s = %s", dialect.QuoteIdentifier(columnName), dialect.Placeholder(idx))
+	}
+
+	var (
+		whereArgumentIndexes = make([][]int, len(p.PrimaryKeyColumnNames))
+		whereClauses         = make([]string, len(p.PrimaryKeyColumnNames))
+	)
+	for idx, columnName := range p.PrimaryKeyColumnNames {
+		whereArgumentIndexes[idx] = p.IndexByColumnName[columnName]
+		whereClauses[idx] = fmt.Sprintf("%s = %s", dialect.QuoteIdentifier(columnName), dialect.Placeholder(idx+len(setClauses)))
+	}
+
+	query := fmt.Sprintf(
+		`UPDATE %s SET %s WHERE %s`,
+		dialect.QuoteIdentifier(p.TableName),
+		strings.Join(setClauses, ", "),
+		strings.Join(whereClauses, " AND "),
+	)
+	return plannedQuery{query, slices.Concat(setArgumentIndexes, whereArgumentIndexes), nil}
+}
+
+func (p plan) buildDeleteQueryIfPossible(dialect Dialect) plannedQuery {
+	if p.TableName == "" || len(p.PrimaryKeyColumnNames) == 0 {
+		return plannedQuery{Query: ""}
+	}
+
+	var (
+		argumentIndexes = make([][]int, len(p.PrimaryKeyColumnNames))
+		clauses         = make([]string, len(p.PrimaryKeyColumnNames))
+	)
+	for idx, columnName := range p.PrimaryKeyColumnNames {
+		argumentIndexes[idx] = p.IndexByColumnName[columnName]
+		clauses[idx] = fmt.Sprintf("%s = %s", dialect.QuoteIdentifier(columnName), dialect.Placeholder(idx))
+	}
+
+	query := fmt.Sprintf(
+		`DELETE FROM %s WHERE %s`,
+		dialect.QuoteIdentifier(p.TableName),
+		strings.Join(clauses, " AND "),
+	)
+	return plannedQuery{query, argumentIndexes, nil}
+}