package water.rapids.ast.prims.string;

import water.MRTask;
import water.fvec.*;
import water.parser.BufferedString;
import water.rapids.Env;
import water.rapids.Val;
import water.rapids.vals.ValFrame;
import water.rapids.ast.AstPrimitive;
import water.rapids.ast.AstRoot;

import java.util.Locale;

/**
 * Accepts a frame with a single string column.
 * Returns a new string column containing the results of the toLower method on each string in the
 * target column.
 * <p/>
 * toLower - Converts all of the characters in this String to lower case.
 */
public class AstToLower extends AstPrimitive {
  @Override
  public String[] args() {
    return new String[]{"ary"};
  }

  @Override
  public int nargs() {
    return 1 + 1;
  } //(tolower x)

  @Override
  public String str() {
    return "tolower";
  }

  @Override
  public ValFrame apply(Env env, Env.StackHelp stk, AstRoot asts[]) {
    Frame fr = stk.track(asts[1].exec(env)).getFrame();
    // Type check
    for (Vec v : fr.vecs())
      if (!(v.isCategorical() || v.isString()))
        throw new IllegalArgumentException("tolower() requires a string or categorical column. "
            + "Received " + fr.anyVec().get_type_str()
            + ". Please convert column to a string or categorical first.");

    // Transform each vec
    Vec nvs[] = new Vec[fr.numCols()];
    int i = 0;
    for (Vec v : fr.vecs()) {
      if (v.isCategorical())
        nvs[i] = toLowerCategoricalCol(v);
      else
        nvs[i] = toLowerStringCol(v);
      i++;
    }

    return new ValFrame(new Frame(nvs));
  }

  private Vec toLowerCategoricalCol(Vec vec) {
    String[] dom = vec.domain().clone();
    for (int i = 0; i < dom.length; ++i)
      dom[i] = dom[i].toLowerCase(Locale.ENGLISH);

    return vec.makeCopy(dom);
  }

  private Vec toLowerStringCol(Vec vec) {
    return new MRTask() {
      @Override
      public void map(Chunk chk, NewChunk newChk) {
        if (chk instanceof C0DChunk) // all NAs
          for (int i = 0; i < chk.len(); i++)
            newChk.addNA();
        else if (((CStrChunk) chk)._isAllASCII) { // fast-path operations
          ((CStrChunk) chk).asciiToLower(newChk);
        } else { //UTF requires Java string methods for accuracy
          BufferedString tmpStr = new BufferedString();
          for (int i = 0; i < chk._len; i++) {
            if (chk.isNA(i))
              newChk.addNA();
            else // Locale.ENGLISH to give the correct results for local insensitive strings
              newChk.addStr(chk.atStr(tmpStr, i).toString().toLowerCase(Locale.ENGLISH));
          }
        }
      }
    }.doAll(new byte[]{Vec.T_STR}, vec).outputFrame().anyVec();
  }
}