PL/pgSQL function that parses PDF timestamps

parse_pdf_date.sql

CREATE OR REPLACE FUNCTION parse_pdf_date(pdf_date TEXT) RETURNS TIMESTAMP WITH TIME ZONE AS $$
DECLARE
    timestamp_part TEXT;
    tz_offset TEXT;
    clean_tz_offset TEXT;
    parsed_timestamp TIMESTAMP;
BEGIN
    -- Return NULL if the input is NULL or does not start with 'D:'
    IF pdf_date IS NULL OR pdf_date !~ '^D:\d+' THEN
        RETURN NULL;
    END IF;

    -- Remove 'D:' prefix
    pdf_date := substring(pdf_date FROM 3);

    -- Handle 'Z00'00'' case by replacing with 'Z'
    pdf_date := regexp_replace(pdf_date, 'Z00''00''$', 'Z');

    -- Extract timestamp part (first 14 digits)
    IF length(pdf_date) >= 14 THEN
        timestamp_part := substring(pdf_date FROM 1 FOR 14);
    ELSE
        RETURN NULL; -- Invalid format (too short)
    END IF;

    -- Validate timestamp before parsing
    IF timestamp_part !~ '^\d{14}$' THEN
        RETURN NULL; -- Invalid timestamp format
    END IF;

    BEGIN
        parsed_timestamp := to_timestamp(timestamp_part, 'YYYYMMDDHH24MISS');
    EXCEPTION
        WHEN others THEN
            RETURN NULL; -- Catch invalid dates (e.g., month > 12)
    END;

    -- Handle timezone if present
    IF pdf_date ~ '^\d{14}[+-]\d{2}''\d{2}''?$' THEN
        tz_offset := substring(pdf_date FROM 15);
        clean_tz_offset := regexp_replace(tz_offset, '''', ':', 'g');
        clean_tz_offset := regexp_replace(clean_tz_offset, ':$', ''); -- Remove trailing colon

        -- Validate timezone format before applying
        IF clean_tz_offset ~ '^[+-]\d{2}:\d{2}$' THEN
            parsed_timestamp := parsed_timestamp AT TIME ZONE ('UTC' || clean_tz_offset);
        END IF;
    END IF;

    RETURN parsed_timestamp;
END;
$$ LANGUAGE plpgsql IMMUTABLE;