package namedconf

import (
	"strings"
)

// maxInline is the widest a block may be to be printed on one line.
const maxInline = 72

// Format returns stmts in canonical form, one statement per line, with
// nested blocks indented by tabs.
func Format(stmts []*Stmt) string {
	var sb strings.Builder
	for _, s := range stmts {
		writeStmt(&sb, s, 0)
	}
	return sb.String()
}

// FormatStmt returns a single statement in canonical form, indented by
// indent tabs, including the trailing newline.
func FormatStmt(s *Stmt, indent int) string {
	var sb strings.Builder
	writeStmt(&sb, s, indent)
	return sb.String()
}

// Compact returns the statement's items on a single line, without the
// trailing semicolon: `allow-query { 10.0.0.0/8; localhost; }`.
func Compact(items []Item) string {
	var sb strings.Builder
	writeItemsInline(&sb, items)
	return sb.String()
}

// CompactStmt returns the statement on a single line with its semicolon.
func CompactStmt(s *Stmt) string { return Compact(s.Items) + ";" }

// FormatValue returns an option's value laid out as named.conf writes it:
// blocks over several lines, indented with tabs. Values without a block,
// and values that don't parse, are returned as they are.
func FormatValue(name, value string) string {
	if !strings.Contains(value, "{") {
		return value
	}
	st, err := ParseOptionValue(name, value)
	if err != nil {
		return value
	}
	out := strings.TrimSuffix(strings.TrimRight(FormatStmt(st, 0), "\n"), ";")
	if rest, ok := strings.CutPrefix(out, st.Keyword()); ok {
		return strings.TrimLeft(rest, " ")
	}
	return value
}

// QuoteString returns s as a named.conf quoted string.
func QuoteString(s string) string {
	var sb strings.Builder
	sb.WriteByte('"')
	for i := 0; i < len(s); i++ {
		if s[i] == '"' || s[i] == '\\' {
			sb.WriteByte('\\')
		}
		sb.WriteByte(s[i])
	}
	sb.WriteByte('"')
	return sb.String()
}

func valueText(v *Value) string {
	if v.Quoted {
		return QuoteString(v.Text)
	}
	return v.Text
}

func writeStmt(sb *strings.Builder, s *Stmt, indent int) {
	tabs := strings.Repeat("\t", indent)
	sb.WriteString(tabs)
	inline := Compact(s.Items)
	if !hasNestedBlocks(s.Items) && len(inline)+indent*8 <= maxInline+8 {
		sb.WriteString(inline)
		sb.WriteString(";\n")
		return
	}
	needSpace := false
	for _, it := range s.Items {
		switch {
		case it.Bang:
			if needSpace {
				sb.WriteByte(' ')
			}
			sb.WriteByte('!')
			needSpace = false
		case it.Value != nil:
			if needSpace {
				sb.WriteByte(' ')
			}
			sb.WriteString(valueText(it.Value))
			needSpace = true
		case it.Block != nil:
			if needSpace {
				sb.WriteByte(' ')
			}
			blockInline := Compact([]Item{it})
			if !blockHasBlocks(it.Block) && len(blockInline) <= 40 {
				sb.WriteString(blockInline)
			} else if len(it.Block.Stmts) == 0 {
				sb.WriteString("{ }")
			} else {
				sb.WriteString("{\n")
				for _, inner := range it.Block.Stmts {
					writeStmt(sb, inner, indent+1)
				}
				sb.WriteString(tabs)
				sb.WriteString("}")
			}
			needSpace = true
		}
	}
	sb.WriteString(";\n")
}

func hasNestedBlocks(items []Item) bool {
	for _, it := range items {
		if it.Block != nil && blockHasBlocks(it.Block) {
			return true
		}
	}
	return false
}

func blockHasBlocks(b *Block) bool {
	for _, s := range b.Stmts {
		for _, it := range s.Items {
			if it.Block != nil {
				return true
			}
		}
	}
	return false
}

func writeItemsInline(sb *strings.Builder, items []Item) {
	needSpace := false
	for _, it := range items {
		switch {
		case it.Bang:
			if needSpace {
				sb.WriteByte(' ')
			}
			sb.WriteByte('!')
			needSpace = false
		case it.Value != nil:
			if needSpace {
				sb.WriteByte(' ')
			}
			sb.WriteString(valueText(it.Value))
			needSpace = true
		case it.Block != nil:
			if needSpace {
				sb.WriteByte(' ')
			}
			if len(it.Block.Stmts) == 0 {
				sb.WriteString("{ }")
			} else {
				sb.WriteString("{ ")
				for _, s := range it.Block.Stmts {
					writeItemsInline(sb, s.Items)
					sb.WriteString("; ")
				}
				sb.WriteString("}")
			}
			needSpace = true
		}
	}
}