package gudusoft.gsqlparser.ir.semantic;

import gudusoft.gsqlparser.TCustomSqlStatement;
import gudusoft.gsqlparser.TSourceToken;

import java.util.Objects;
import java.util.Optional;

/**
 * Keeps a statement slice and global {@link SourceSpan} coordinates tied to
 * the same original SQL text.
 *
 * <p>GSP spans use global, 1-based line/column coordinates, while
 * {@link AnalysisResult#getStatementText()} is trimmed and has one trailing
 * semicolon removed. Consumers should therefore use {@link #slice(SourceSpan)}
 * instead of applying a global span directly to the per-statement string.
 */
public final class StatementSourceView {

    private final String fullSql;
    private final String statementText;
    private final long statementStartOffset;
    private final long statementStartLine;
    private final long statementStartColumn;

    private StatementSourceView(String fullSql, String statementText,
                                long statementStartOffset,
                                long statementStartLine,
                                long statementStartColumn) {
        this.fullSql = fullSql;
        this.statementText = statementText;
        this.statementStartOffset = statementStartOffset;
        this.statementStartLine = statementStartLine;
        this.statementStartColumn = statementStartColumn;
    }

    /** Build a view from the original input and one parsed statement. */
    public static StatementSourceView of(String fullSql, TCustomSqlStatement statement) {
        Objects.requireNonNull(fullSql, "fullSql");
        Objects.requireNonNull(statement, "statement");

        TSourceToken startToken = statement.getStartToken();
        TSourceToken endToken = statement.getEndToken();
        long startOffset = startToken == null ? -1L : startToken.offset;
        long startLine = startToken == null ? -1L : startToken.lineNo;
        long startColumn = startToken == null ? -1L : startToken.columnNo;

        String text = sourceStatementText(fullSql, statement, startToken, endToken);
        return new StatementSourceView(fullSql, text, startOffset,
                startLine, startColumn);
    }

    public String getFullSql() {
        return fullSql;
    }

    /**
     * Return the analyzer-compatible statement text: surrounding whitespace
     * and one trailing statement separator are removed.
     */
    public String getStatementText() {
        return statementText;
    }

    /** @return global character offset, or {@code -1} when tokens lack one. */
    public long getStatementStartOffset() {
        return statementStartOffset;
    }

    /** @return global 1-based line, or {@code -1} when unavailable. */
    public long getStatementStartLine() {
        return statementStartLine;
    }

    /** @return global 1-based column, or {@code -1} when unavailable. */
    public long getStatementStartColumn() {
        return statementStartColumn;
    }

    /**
     * Slice a global half-open span from the original SQL text.
     *
     * @return empty when either coordinate is outside the source or the end
     *         precedes the start
     */
    public Optional<String> slice(SourceSpan span) {
        if (span == null) return Optional.empty();
        int start = offsetOf(span.getStartLine(), span.getStartColumn());
        int end = offsetOf(span.getEndLine(), span.getEndColumn());
        if (start < 0 || end < start) return Optional.empty();
        return Optional.of(fullSql.substring(start, end));
    }

    private int offsetOf(long targetLine, long targetColumn) {
        if (targetLine < 1 || targetColumn < 1) return -1;
        long line = 1;
        long column = 1;
        for (int i = 0; i < fullSql.length(); i++) {
            if (line == targetLine && column == targetColumn) return i;
            char ch = fullSql.charAt(i);
            if (ch == '\n') {
                line++;
                column = 1;
            } else {
                column++;
            }
        }
        return line == targetLine && column == targetColumn
                ? fullSql.length() : -1;
    }

    private static String sourceStatementText(String sql,
                                              TCustomSqlStatement statement,
                                              TSourceToken start,
                                              TSourceToken end) {
        if (start != null && end != null
                && start.offset >= 0 && start.offset <= Integer.MAX_VALUE
                && end.offset >= 0 && end.offset <= Integer.MAX_VALUE) {
            int startOffset = (int) start.offset;
            String endText = end.getAstext();
            long endOffsetLong = end.offset + (endText == null ? 0 : endText.length());
            if (endOffsetLong <= Integer.MAX_VALUE) {
                int endOffset = (int) endOffsetLong;
                if (endOffset >= startOffset && endOffset <= sql.length()) {
                    String slice = sql.substring(startOffset, endOffset).trim();
                    if (slice.endsWith(";")) {
                        slice = slice.substring(0, slice.length() - 1).trim();
                    }
                    return slice;
                }
            }
        }
        try {
            return statement.toString();
        } catch (RuntimeException ex) {
            return null;
        }
    }
}