// Copyright 2023 Huan Du. All rights reserved.
// Licensed under the MIT license that can be found in the LICENSE file.

package sqlbuilder

import (
	"io"
	"strings"
)

type stringBuilder struct {
	builder *strings.Builder
}

var _ io.Writer = new(stringBuilder)

func newStringBuilder() *stringBuilder {
	return &stringBuilder{
		builder: &strings.Builder{},
	}
}

// WriteLeadingString writes s to internal buffer.
// If it's not the first time to write the string, a blank (" ") will be written before s.
func (sb *stringBuilder) WriteLeadingString(s string) {
	if sb.builder.Len() > 0 {
		sb.builder.WriteString(" ")
	}

	sb.builder.WriteString(s)
}

func (sb *stringBuilder) WriteString(s string) {
	sb.builder.WriteString(s)
}

func (sb *stringBuilder) WriteStrings(ss []string, sep string) {
	if len(ss) == 0 {
		return
	}

	firstAdded := false
	if len(ss[0]) != 0 {
		sb.WriteString(ss[0])
		firstAdded = true
	}

	for _, s := range ss[1:] {
		if len(s) != 0 {
			if firstAdded {
				sb.WriteString(sep)
			}
			sb.WriteString(s)
			firstAdded = true
		}
	}
}

func (sb *stringBuilder) WriteStringsPrefixed(prefix string, ss []string, sep string) {
	prefixedSs := []string{}

	for _, s := range ss {
		prefixedSs = append(prefixedSs, prefix+s)
	}

	sb.WriteStrings(prefixedSs, sep)
}

func (sb *stringBuilder) WriteRune(r rune) {
	sb.builder.WriteRune(r)
}

func (sb *stringBuilder) Write(data []byte) (int, error) {
	return sb.builder.Write(data)
}

func (sb *stringBuilder) String() string {
	return sb.builder.String()
}

func (sb *stringBuilder) Reset() {
	sb.builder.Reset()
}

func (sb *stringBuilder) Grow(n int) {
	sb.builder.Grow(n)
}

// filterEmptyStrings removes empty strings from ss.
// As ss rarely contains empty strings, filterEmptyStrings tries to avoid allocation if possible.
func filterEmptyStrings(ss []string) []string {
	emptyStrings := 0

	for _, s := range ss {
		if len(s) == 0 {
			emptyStrings++
		}
	}

	if emptyStrings == 0 {
		return ss
	}

	filtered := make([]string, 0, len(ss)-emptyStrings)

	for _, s := range ss {
		if len(s) != 0 {
			filtered = append(filtered, s)
		}
	}

	return filtered
}