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package org.hl7.fhir.r4.utils;

/*
  Copyright (c) 2011+, HL7, Inc.
  All rights reserved.
  
  Redistribution and use in source and binary forms, with or without modification, 
  are permitted provided that the following conditions are met:
    
   * Redistributions of source code must retain the above copyright notice, this 
     list of conditions and the following disclaimer.
   * Redistributions in binary form must reproduce the above copyright notice, 
     this list of conditions and the following disclaimer in the documentation 
     and/or other materials provided with the distribution.
   * Neither the name of HL7 nor the names of its contributors may be used to 
     endorse or promote products derived from this software without specific 
     prior written permission.
  
  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND 
  ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED 
  WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 
  IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, 
  INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 
  NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR 
  PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, 
  WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 
  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 
  POSSIBILITY OF SUCH DAMAGE.
  
 */

import java.util.ArrayList;
import java.util.List;

import org.hl7.fhir.exceptions.FHIRException;
import org.hl7.fhir.utilities.Utilities;

public class SnomedExpressions {

  public class Base {
    private int stop;
    private int start;

    public int getStop() {
      return stop;
    }

    public void setStop(int stop) {
      this.stop = stop;
    }

    public int getStart() {
      return start;
    }

    public void setStart(int start) {
      this.start = start;
    }
  }

  public class Concept extends Base {
    private long reference;
    private String code;
    private String description;
    private String literal;
    private String decimal;

    public long getReference() {
      return reference;
    }

    public void setReference(long reference) {
      this.reference = reference;
    }

    public String getCode() {
      return code;
    }

    public void setCode(String code) {
      this.code = code;
    }

    public String getDescription() {
      return description;
    }

    public void setDescription(String description) {
      this.description = description;
    }

    public String getLiteral() {
      return literal;
    }

    public void setLiteral(String literal) {
      this.literal = literal;
    }

    public String getDecimal() {
      return decimal;
    }

    public void setDecimal(String decimal) {
      this.decimal = decimal;
    }

    @Override
    public String toString() {
      if (code != null)
        return code;
      else if (decimal != null)
        return "#" + decimal;
      else if (literal != null)
        return "\"" + literal + "\"";
      else
        return "";
    }
  }

  public enum ExpressionStatus {
    Unknown, Equivalent, SubsumedBy;
  }

  public class Expression extends Base {
    private List refinementGroups = new ArrayList();
    private List refinements = new ArrayList();
    private List concepts = new ArrayList();
    private ExpressionStatus status;

    public ExpressionStatus getStatus() {
      return status;
    }

    public void setStatus(ExpressionStatus status) {
      this.status = status;
    }

    public List getRefinementGroups() {
      return refinementGroups;
    }

    public List getRefinements() {
      return refinements;
    }

    public List getConcepts() {
      return concepts;
    }

    @Override
    public String toString() {
      StringBuilder b = new StringBuilder();
      if (status == ExpressionStatus.Equivalent)
        b.append("===");
      else if (status == ExpressionStatus.SubsumedBy)
        b.append("<<<");
      boolean first = true;
      for (Concept concept : concepts) {
        if (first)
          first = false;
        else
          b.append(',');
        b.append(concept.toString());
      }
      for (Refinement refinement : refinements) {
        if (first)
          first = false;
        else
          b.append(',');
        b.append(refinement.toString());
      }
      for (RefinementGroup refinementGroup : refinementGroups) {
        if (first)
          first = false;
        else
          b.append(',');
        b.append(refinementGroup.toString());
      }
      return b.toString();
    }
  }

  public class Refinement extends Base {
    private Concept name;
    private Expression value;

    public Concept getName() {
      return name;
    }

    public void setName(Concept name) {
      this.name = name;
    }

    public Expression getValue() {
      return value;
    }

    public void setValue(Expression value) {
      this.value = value;
    }

    @Override
    public String toString() {
      return name.toString() + "=" + value.toString();
    }
  }

  public class RefinementGroup extends Base {
    private List refinements = new ArrayList();

    public List getRefinements() {
      return refinements;
    }

    @Override
    public String toString() {
      StringBuilder b = new StringBuilder();
      boolean first = true;
      for (Refinement refinement : refinements) {
        if (first)
          first = false;
        else
          b.append(',');
        b.append(refinement.toString());
      }
      return b.toString();
    }
  }

  private static final int MAX_TERM_LIMIT = 1024;

  private String source;
  private int cursor;

  private Concept concept() throws FHIRException {
    Concept res = new Concept();
    res.setStart(cursor);
    ws();
    if (peek() == '#')
      res.decimal = decimal();
    else if (peek() == '"')
      res.literal = stringConstant();
    else
      res.code = conceptId();
    ws();
    if (gchar('|')) {
      ws();
      res.description = term().trim();
      ws();
      fixed('|');
      ws();
    }
    res.setStop(cursor);
    return res;
  }

  private void refinements(Expression expr) throws FHIRException {
    boolean n = true;
    while (n) {
      if (peek() != '{')
        expr.refinements.add(attribute());
      else
        expr.refinementGroups.add(attributeGroup());
      ws();
      n = gchar(',');
      ws();
    }
  }

  private RefinementGroup attributeGroup() throws FHIRException {
    RefinementGroup res = new RefinementGroup();
    fixed('{');
    ws();
    res.setStart(cursor);
    res.refinements.add(attribute());
    while (gchar(','))
      res.refinements.add(attribute());
    res.setStop(cursor);
    ws();
    fixed('}');
    ws();
    return res;
  }

  private Refinement attribute() throws FHIRException {
    Refinement res = new Refinement();
    res.setStart(cursor);
    res.name = attributeName();
    fixed('=');
    res.value = attributeValue();
    ws();
    res.setStop(cursor);
    return res;
  }

  private Concept attributeName() throws FHIRException {
    Concept res = new Concept();
    res.setStart(cursor);
    ws();
    res.code = conceptId();
    ws();
    if (gchar('|')) {
      ws();
      res.description = term();
      ws();
      fixed('|');
      ws();
    }
    res.setStop(cursor);
    return res;
  }

  private Expression attributeValue() throws FHIRException {
    Expression res;
    ws();
    if (gchar('(')) {
      res = expression();
      fixed(')');
    } else {
      res = expression();
    }
    return res;
  }

  private Expression expression() throws FHIRException {
    Expression res = new Expression();
    res.setStart(cursor);
    ws();
    res.concepts.add(concept());
    while (gchar('+'))
      res.concepts.add(concept());
    if (gchar(':')) {
      ws();
      refinements(res);
    }
    res.setStop(cursor);
    return res;
  }

  private String conceptId() throws FHIRException {
    StringBuffer res = new StringBuffer(Utilities.padLeft("", ' ', 18));
    int i = 0;
    while (peek() >= '0' && peek() <= '9') {
      res.setCharAt(i, next());
      i++;
    }
    rule(i > 0, "Concept not found (next char = \"" + peekDisp() + "\", in '" + source + "')");
    return res.substring(0, i);
  }

  private String decimal() throws FHIRException {
    StringBuffer res = new StringBuffer(Utilities.padLeft("", ' ', MAX_TERM_LIMIT));
    int i = 0;
    fixed('#');
    while ((peek() >= '0' && peek() <= '9') || peek() == '.') {
      res.setCharAt(i, next());
      i++;
    }
    return res.substring(0, i);
  }

  private String term() {
    StringBuffer res = new StringBuffer(Utilities.padLeft("", ' ', MAX_TERM_LIMIT));
    int i = 0;
    while (peek() != '|') {
      res.setCharAt(i, next());
      i++;
    }
    return res.substring(0, i);
  }

  private void ws() {
    while (Utilities.existsInList(peek(), ' ', '\t', '\r', 'n'))
      next();
  }

  private boolean gchar(char ch) {
    boolean result = peek() == ch;
    if (result)
      next();
    return result;
  }

  private void fixed(char ch) throws FHIRException {
    boolean b = gchar(ch);
    rule(b, "Expected character \"" + ch + "\" but found " + peek());
    ws();
  }

  private Expression parse() throws FHIRException {
    Expression res = new Expression();
    res.setStart(cursor);
    ws();
    if (peek() == '=') {
      res.status = ExpressionStatus.Equivalent;
      prefix('=');
    } else if (peek() == '<') {
      res.status = ExpressionStatus.SubsumedBy;
      prefix('<');
    }

    res.concepts.add(concept());
    while (gchar('+'))
      res.concepts.add(concept());
    if (gchar(':')) {
      ws();
      refinements(res);
    }
    res.setStop(cursor);
    rule(cursor >= source.length(), "Found content (\"" + peekDisp() + "\") after end of expression");
    return res;
  }

  public static Expression parse(String source) throws FHIRException {
    SnomedExpressions self = new SnomedExpressions();
    self.source = source;
    self.cursor = 0;
    return self.parse();
  }

  private char peek() {
    if (cursor >= source.length())
      return '\0';
    else
      return source.charAt(cursor);
  }

  private String peekDisp() {
    if (cursor >= source.length())
      return "[n/a: overrun]";
    else
      return String.valueOf(source.charAt(cursor));
  }

  private void prefix(char c) throws FHIRException {
    fixed(c);
    fixed(c);
    fixed(c);
    ws();
  }

  private char next() {
    char res = peek();
    cursor++;
    return res;
  }

  private void rule(boolean test, String message) throws FHIRException {
    if (!test)
      throw new FHIRException(message + " at character " + Integer.toString(cursor));
  }

  private String stringConstant() throws FHIRException {
    StringBuffer res = new StringBuffer(Utilities.padLeft("", ' ', MAX_TERM_LIMIT));
    fixed('"');
    int i = 0;
    while (peek() != '"') {
      i++;
      res.setCharAt(i, next());
    }
    fixed('"');
    return res.substring(0, i);
  }

}