initial pase store definitions

store/dialect.go

@@ -0,0 +1,70 @@
+package store
+
+import (
+	"strconv"
+	"strings"
+)
+
+// Dialect captures the small syntactic differences between SQL backends.
+// All queries are written with ? placeholders; Rebind rewrites them as
+// needed for the target driver. Semantic differences (e.g., RETURNING
+// support) are not the Dialect's concern — they belong in separate Store
+// implementations.
+type Dialect interface {
+	Rebind(query string) string
+}
+
+// SQLiteDialect leaves queries unchanged; database/sql + the SQLite driver
+// already accept ? placeholders.
+type SQLiteDialect struct{}
+
+func (SQLiteDialect) Rebind(query string) string { return query }
+
+// PostgresDialect rewrites ? placeholders into $1, $2, ... while leaving
+// any ? characters that appear inside single-quoted string literals or
+// double-quoted identifiers untouched.
+type PostgresDialect struct{}
+
+func (PostgresDialect) Rebind(query string) string {
+	var b strings.Builder
+	b.Grow(len(query) + 8)
+
+	n := 0
+	i := 0
+	for i < len(query) {
+		c := query[i]
+		switch c {
+		case '\'', '"':
+			// Copy the entire quoted span verbatim, handling doubled-quote escapes.
+			quote := c
+			b.WriteByte(c)
+			i++
+			for i < len(query) {
+				if query[i] == quote {
+					if i+1 < len(query) && query[i+1] == quote {
+						// Escaped quote: '' or "". Copy both bytes and continue.
+						b.WriteByte(quote)
+						b.WriteByte(quote)
+						i += 2
+						continue
+					}
+					b.WriteByte(quote)
+					i++
+					break
+				}
+				b.WriteByte(query[i])
+				i++
+			}
+		case '?':
+			n++
+			b.WriteByte('$')
+			b.WriteString(strconv.Itoa(n))
+			i++
+		default:
+			b.WriteByte(c)
+			i++
+		}
+	}
+
+	return b.String()
+}