chore: import upstream snapshot with attribution

server/functions/substr.go

@@ -0,0 +1,161 @@
+// Copyright 2024 Dolthub, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package functions
+
+import (
+	"fmt"
+	"regexp"
+
+	"github.com/cockroachdb/errors"
+	"github.com/dolthub/go-mysql-server/sql"
+
+	"github.com/dolthub/doltgresql/server/functions/framework"
+	pgtypes "github.com/dolthub/doltgresql/server/types"
+)
+
+// initSubstr registers the functions to the catalog.
+func initSubstr() {
+	framework.RegisterFunction(substr_text_int32)
+	framework.RegisterFunction(substring_text_int32)
+	framework.RegisterFunction(substr_text_int32_int32)
+	framework.RegisterFunction(substring_text_int32_int32)
+	framework.RegisterFunction(substring_text_text)
+}
+
+// substr_text_int32 represents the PostgreSQL function of the same name, taking the same parameters.
+var substr_text_int32 = framework.Function2{
+	Name:       "substr",
+	Return:     pgtypes.Text,
+	Parameters: [2]*pgtypes.DoltgresType{pgtypes.Text, pgtypes.Int32},
+	Strict:     true,
+	Callable:   substring_text_int32_fn,
+}
+
+// substring_text_int32 represents the PostgreSQL function of the same name, taking the same parameters.
+var substring_text_int32 = framework.Function2{
+	Name:       "substring",
+	Return:     pgtypes.Text,
+	Parameters: [2]*pgtypes.DoltgresType{pgtypes.Text, pgtypes.Int32},
+	Strict:     true,
+	Callable:   substring_text_int32_fn,
+}
+
+// substring_text_int32_fn is a helper function for substr_text_int32 and substring_text_int32.
+func substring_text_int32_fn(ctx *sql.Context, _ [3]*pgtypes.DoltgresType, input any, start any) (any, error) {
+	str, ok, err := sql.Unwrap[string](ctx, input)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		return nil, fmt.Errorf("unexpected type for substring input, expected string, got %T", str)
+	}
+	runes := []rune(str)
+	if start.(int32) < 1 {
+		start = int32(1)
+	}
+	// start is 1-indexed
+	start = start.(int32) - int32(1)
+	if int(start.(int32)) >= len(runes) {
+		return "", nil
+	}
+	return string(runes[start.(int32):]), nil
+}
+
+// substr_text_int32_int32 represents the PostgreSQL function of the same name, taking the same parameters.
+var substr_text_int32_int32 = framework.Function3{
+	Name:       "substr",
+	Return:     pgtypes.Text,
+	Parameters: [3]*pgtypes.DoltgresType{pgtypes.Text, pgtypes.Int32, pgtypes.Int32},
+	Strict:     true,
+	Callable:   substring_text_int32_int32_fn,
+}
+
+// substr_text_int32_int32 represents the PostgreSQL function of the same name, taking the same parameters.
+var substring_text_int32_int32 = framework.Function3{
+	Name:       "substring",
+	Return:     pgtypes.Text,
+	Parameters: [3]*pgtypes.DoltgresType{pgtypes.Text, pgtypes.Int32, pgtypes.Int32},
+	Strict:     true,
+	Callable:   substring_text_int32_int32_fn,
+}
+
+// substring_text_int32_int32_fn is a helper function for substr_text_int32_int32.
+func substring_text_int32_int32_fn(ctx *sql.Context, _ [4]*pgtypes.DoltgresType, input any, startInt any, countInt any) (any, error) {
+	str, ok, err := sql.Unwrap[string](ctx, input)
+	if err != nil {
+		return nil, err
+	}
+	if !ok {
+		return nil, fmt.Errorf("unexpected type for substring input, expected string, got %T", str)
+	}
+	start := startInt.(int32)
+	count := countInt.(int32)
+	runes := []rune(str)
+	if count < 0 {
+		return nil, errors.Errorf("negative substring length not allowed")
+	}
+	// start is 1-indexed
+	start--
+	if start < 0 {
+		count += start
+		start = 0
+	}
+	if count <= 0 {
+		return "", nil
+	}
+	if int(start) >= len(runes) {
+		return "", nil
+	} else if int64(start)+int64(count) > int64(len(runes)) {
+		return string(runes[start:]), nil
+	}
+	return string(runes[start : start+count]), nil
+}
+
+// substr_text_text represents the PostgreSQL function of the same name, taking the same parameters.
+// This is a form of the syntax `substring(string from pattern)`.
+var substring_text_text = framework.Function2{
+	Name:       "substring",
+	Return:     pgtypes.Text,
+	Parameters: [2]*pgtypes.DoltgresType{pgtypes.Text, pgtypes.Text},
+	Strict:     true,
+	Callable: func(ctx *sql.Context, _ [3]*pgtypes.DoltgresType, input any, pattern any) (any, error) {
+		str, ok, err := sql.Unwrap[string](ctx, input)
+		if err != nil {
+			return nil, err
+		}
+		if !ok {
+			return nil, fmt.Errorf("unexpected type for substring input, expected string, got %T", str)
+		}
+		patternStr, ok, err := sql.Unwrap[string](ctx, pattern)
+		if err != nil {
+			return nil, err
+		}
+		if !ok {
+			return nil, fmt.Errorf("unexpected type for substring pattern, expected string, got %T", str)
+		}
+		re, err := regexp.Compile(patternStr)
+		if err != nil {
+			return nil, err
+		}
+
+		match := re.Find([]byte(str))
+
+		if match == nil {
+			return nil, nil
+		}
+
+		return string(match), nil
+	},
+}