// Package pgast wraps go-pgquery (libpg_query compiled to WASM via wazero, no
// cgo) to produce a PostgreSQL parse tree from a SQL string.
//
// The concrete node types live in github.com/pganalyze/pg_query_go/v6 and are
// generated from the PostgreSQL source; callers import that package directly
// when walking the tree.
package pgast

import (
	"strings"

	pg_query "github.com/pganalyze/pg_query_go/v6"
	waspg "github.com/wasilibs/go-pgquery"
)

// ParseResult is re-exported so callers don't need to import both packages.
type ParseResult = pg_query.ParseResult

// Parse parses sql and returns the PostgreSQL parse tree. The returned error
// is a pg_query parse error containing a message and location; it is safe to
// display to the user.
func Parse(sql string) (*ParseResult, error) {
	return waspg.Parse(sql)
}

// FirstTokenOffset advances past whitespace and SQL comments (-- line and
// /* block */) from start, returning the byte offset of the first real token.
// This is needed because RawStmt.StmtLocation points to the start of the
// statement "block" which includes any preceding comments, not to the first
// keyword token.
func FirstTokenOffset(sql string, start int) int {
	i := start
	n := len(sql)
	for i < n {
		switch {
		case sql[i] == ' ' || sql[i] == '\t' || sql[i] == '\r' || sql[i] == '\n':
			i++
		case i+1 < n && sql[i] == '-' && sql[i+1] == '-':
			for i < n && sql[i] != '\n' {
				i++
			}
		case i+1 < n && sql[i] == '/' && sql[i+1] == '*':
			i += 2
			for i+1 < n && !(sql[i] == '*' && sql[i+1] == '/') {
				i++
			}
			if i+1 < n {
				i += 2
			}
		default:
			return i
		}
	}
	return start
}

// LocationToLineCol converts a 0-based byte offset into a 1-based (line, col)
// pair. Returns (1, 1) for a negative offset.
func LocationToLineCol(sql string, offset int) (line, col int) {
	if offset < 0 {
		return 1, 1
	}
	if offset > len(sql) {
		offset = len(sql)
	}
	before := sql[:offset]
	line = strings.Count(before, "\n") + 1
	lastNL := strings.LastIndex(before, "\n")
	if lastNL < 0 {
		col = offset + 1
	} else {
		col = offset - lastNL
	}
	return line, col
}