package format

import (
	"strings"

	"git.warky.dev/wdevs/pgtidy/pkg/lexer"
)

// SemanticallyEqual reports whether a and b have the same non-trivia token
// stream, i.e. formatting may only ever change whitespace/comment trivia and
// layout — it must never add, remove, or alter a token of actual code.
// Unquoted identifiers/keywords compare case-insensitively (casing is a
// style choice); everything else (strings, numbers, operators, punctuation)
// must match exactly. Dollar-quoted body tokens are compared recursively so
// that independent body reformatting doesn't trigger a false failure.
//
// The CLI and LSP must call this before ever writing or emitting formatted
// output: if it returns false, the formatter has a bug and the original
// source must be kept, never the (corrupting) formatted output.
func SemanticallyEqual(a, b string) bool {
	ta := significantTokens(a)
	tb := significantTokens(b)
	if len(ta) != len(tb) {
		return false
	}
	for i := range ta {
		if ta[i].Kind != tb[i].Kind {
			return false
		}
		switch ta[i].Kind {
		case lexer.Ident:
			if !strings.EqualFold(ta[i].Text, tb[i].Text) {
				return false
			}
		case lexer.DollarString:
			_, innerA, _, okA := splitDollarQuote(ta[i].Text)
			_, innerB, _, okB := splitDollarQuote(tb[i].Text)
			if okA != okB || (okA && !SemanticallyEqual(innerA, innerB)) {
				return false
			}
		default:
			if ta[i].Text != tb[i].Text {
				return false
			}
		}
	}
	return true
}

// significantTokens lexes src and returns its tokens excluding EOF and trivia
// (whitespace/comments).
func significantTokens(src string) []lexer.Token {
	var out []lexer.Token
	for _, t := range lexer.Lex(src) {
		if t.Kind == lexer.EOF || t.IsTrivia() {
			continue
		}
		out = append(out, t)
	}
	return out
}