import { isIdentifierStart, isIdentifierChar } from "../util/identifier";
import { types as tt, keywords as keywordTypes } from "./types";
import { SourceLocation } from "../locutil";
import { lineBreak, lineBreakG, isNewLine, nonASCIIwhitespace } from "../util/whitespace";

// Object type used to represent tokens. Note that normally, tokens
// simply exist as properties on the parser object. This is only
// used for the onToken callback and the external tokenizer.

export class Token {
  constructor(p) {
    this.type = p.type;
    this.value = p.value;
    this.start = p.start;
    this.end = p.end;

    this.loc = new SourceLocation(p.startLoc, p.endLoc);
  }
}

// ## Tokenizer

// Are we running under Rhino?
/* global Packages */
const isRhino = typeof Packages === "object" && Object.prototype.toString.call(Packages) === "[object JavaPackage]";

// Parse a regular expression. Some context-awareness is necessary,
// since a '/' inside a '[]' set does not end the expression.

function tryCreateRegexp(src, flags, throwErrorStart) {
  try {
    return new RegExp(src, flags);
  } catch (e) {
    if (throwErrorStart !== undefined) {
      if (e instanceof SyntaxError) this.raise(throwErrorStart, "Error parsing regular expression: " + e.message);
      this.raise(e);
    }
  }
}

var regexpUnicodeSupport = !!tryCreateRegexp("\uffff", "u");

function codePointToString(code) {
  // UTF-16 Decoding
  if (code <= 0xFFFF) return String.fromCharCode(code);
  return String.fromCharCode(((code - 0x10000) >> 10) + 0xD800, ((code - 0x10000) & 1023) + 0xDC00);
}

// Used to signal to callers of `readWord1` whether the word
// contained any escape sequences. This is needed because words with
// escape sequences must not be interpreted as keywords.

var containsEsc;

export default class Tokenizer {
  constructor() {
    // The current position of the tokenizer in the input.
    this.pos = this.lineStart = 0;
    this.curLine = 1;

    // Properties of the current token:
    // Its type
    this.type = tt.eof;
    // For tokens that include more information than their type, the value
    this.value = null;
    // Its start and end offset
    this.start = this.end = this.pos;
    // And, if locations are used, the {line, column} object
    // corresponding to those offsets
    this.startLoc = this.endLoc = this.curPosition();

    // Position information for the previous token
    this.lastTokEndLoc = this.lastTokStartLoc = null;
    this.lastTokStart = this.lastTokEnd = this.pos;

    // The context stack is used to superficially track syntactic
    // context to predict whether a regular expression is allowed in a
    // given position.
    this.context = this.initialContext();
    this.exprAllowed = true;
  }

  // Move to the next token

  next() {
    if (!this.isLookahead) {
      this.tokens.push(new Token(this));
    }

    this.lastTokEnd = this.end;
    this.lastTokStart = this.start;
    this.lastTokEndLoc = this.endLoc;
    this.lastTokStartLoc = this.startLoc;
    this.nextToken();
  };

  getToken() {
    this.next();
    return new Token(this);
  }

  // Toggle strict mode. Re-reads the next number or string to please
  // pedantic tests (`"use strict"; 010;` should fail).

  setStrict(strict) {
    this.strict = strict;
    if (this.type !== tt.num && this.type !== tt.string) return;
    this.pos = this.start;
    while (this.pos < this.lineStart) {
      this.lineStart = this.input.lastIndexOf("\n", this.lineStart - 2) + 1;
      --this.curLine;
    }
    this.nextToken();
  }

  curContext() {
    return this.context[this.context.length - 1];
  }

  // Read a single token, updating the parser object's token-related
  // properties.

  nextToken() {
    let curContext = this.curContext();
    if (!curContext || !curContext.preserveSpace) this.skipSpace();

    this.start = this.pos;
    this.startLoc = this.curPosition();
    if (this.pos >= this.input.length) return this.finishToken(tt.eof);

    if (curContext.override) {
      return curContext.override(this);
    } else {
      return this.readToken(this.fullCharCodeAtPos());
    }
  }

  readToken(code) {
    // Identifier or keyword. '\uXXXX' sequences are allowed in
    // identifiers, so '\' also dispatches to that.
    if (isIdentifierStart(code, true) || code === 92 /* '\' */)
      return this.readWord();

    return this.getTokenFromCode(code);
  }

  fullCharCodeAtPos() {
    let code = this.input.charCodeAt(this.pos);
    if (code <= 0xd7ff || code >= 0xe000) return code;

    let next = this.input.charCodeAt(this.pos + 1);
    return (code << 10) + next - 0x35fdc00;
  }

  pushComment(block, text, start, end, startLoc, endLoc) {
    var comment = {
      type: block ? "CommentBlock" : "CommentLine",
      value: text,
      start: start,
      end: end,
      loc: new SourceLocation(startLoc, endLoc),
      range: [start, end]
    };

    this.tokens.push(comment);
    this.comments.push(comment);
    this.addComment(comment);
  }

  skipBlockComment() {
    let startLoc = this.curPosition();
    let start = this.pos, end = this.input.indexOf("*/", this.pos += 2);
    if (end === -1) this.raise(this.pos - 2, "Unterminated comment");

    this.pos = end + 2;
    lineBreakG.lastIndex = start;
    let match;
    while ((match = lineBreakG.exec(this.input)) && match.index < this.pos) {
      ++this.curLine;
      this.lineStart = match.index + match[0].length;
    }

    this.pushComment(true, this.input.slice(start + 2, end), start, this.pos, startLoc, this.curPosition());
  }

  skipLineComment(startSkip) {
    let start = this.pos;
    let startLoc = this.curPosition();
    let ch = this.input.charCodeAt(this.pos += startSkip);
    while (this.pos < this.input.length && ch !== 10 && ch !== 13 && ch !== 8232 && ch !== 8233) {
      ++this.pos;
      ch = this.input.charCodeAt(this.pos);
    }

    this.pushComment(false, this.input.slice(start + startSkip, this.pos), start, this.pos, startLoc, this.curPosition());
  }

  // Called at the start of the parse and after every token. Skips
  // whitespace and comments, and.

  skipSpace() {
    loop: while (this.pos < this.input.length) {
      let ch = this.input.charCodeAt(this.pos);
      switch (ch) {
        case 32: case 160: // ' '
          ++this.pos;
          break;

        case 13:
          if (this.input.charCodeAt(this.pos + 1) === 10) {
            ++this.pos;
          }

        case 10: case 8232: case 8233:
          ++this.pos;
          ++this.curLine;
          this.lineStart = this.pos;
          break;

        case 47: // '/'
          switch (this.input.charCodeAt(this.pos + 1)) {
            case 42: // '*'
              this.skipBlockComment();
              break;

            case 47:
              this.skipLineComment(2);
              break;

            default:
              break loop;
          }
          break;

        default:
          if (ch > 8 && ch < 14 || ch >= 5760 && nonASCIIwhitespace.test(String.fromCharCode(ch))) {
            ++this.pos;
          } else {
            break loop;
          }
      }
    }
  }

  // Called at the end of every token. Sets `end`, `val`, and
  // maintains `context` and `exprAllowed`, and skips the space after
  // the token, so that the next one's `start` will point at the
  // right position.

  finishToken(type, val) {
    this.end = this.pos;
    this.endLoc = this.curPosition();
    let prevType = this.type;
    this.type = type;
    this.value = val;

    this.updateContext(prevType);
  }

  // ### Token reading

  // This is the function that is called to fetch the next token. It
  // is somewhat obscure, because it works in character codes rather
  // than characters, and because operator parsing has been inlined
  // into it.
  //
  // All in the name of speed.
  //
  readToken_dot() {
    let next = this.input.charCodeAt(this.pos + 1);
    if (next >= 48 && next <= 57) return this.readNumber(true);

    let next2 = this.input.charCodeAt(this.pos + 2);
    if (next === 46 && next2 === 46) { // 46 = dot '.'
      this.pos += 3;
      return this.finishToken(tt.ellipsis);
    } else {
      ++this.pos;
      return this.finishToken(tt.dot);
    }
  }

  readToken_slash() { // '/'
    let next = this.input.charCodeAt(this.pos + 1);
    if (this.exprAllowed) {
      ++this.pos;
      return this.readRegexp();
    }
    if (next === 61) return this.finishOp(tt.assign, 2);
    return this.finishOp(tt.slash, 1);
  }

  readToken_mult_modulo(code) { // '%*'
    var type = code === 42 ? tt.star : tt.modulo;
    var width = 1;
    var next = this.input.charCodeAt(this.pos + 1);

    if (next === 42 && this.options.features["es7.exponentiationOperator"]) { // '*'
      width++;
      next = this.input.charCodeAt(this.pos + 2);
      type = tt.exponent;
    }

    if (next === 61) {
      width++;
      type = tt.assign;
    }

    return this.finishOp(type, width);
  }

  readToken_pipe_amp(code) { // '|&'
    let next = this.input.charCodeAt(this.pos + 1);
    if (next === code) return this.finishOp(code === 124 ? tt.logicalOR : tt.logicalAND, 2);
    if (next === 61) return this.finishOp(tt.assign, 2);
    return this.finishOp(code === 124 ? tt.bitwiseOR : tt.bitwiseAND, 1);
  }

  readToken_caret() { // '^'
    let next = this.input.charCodeAt(this.pos + 1);
    if (next === 61) {
      return this.finishOp(tt.assign, 2);
    } else {
      return this.finishOp(tt.bitwiseXOR, 1);
    }
  }

  readToken_plus_min(code) { // '+-'
    let next = this.input.charCodeAt(this.pos + 1);

    if (next === code) {
      if (next === 45 && this.input.charCodeAt(this.pos + 2) === 62 && lineBreak.test(this.input.slice(this.lastTokEnd, this.pos))) {
        // A `-->` line comment
        this.skipLineComment(3);
        this.skipSpace();
        return this.nextToken();
      }
      return this.finishOp(tt.incDec, 2);
    }

    if (next === 61) {
      return this.finishOp(tt.assign, 2);
    } else {
      return this.finishOp(tt.plusMin, 1);
    }
  }

  readToken_lt_gt(code) { // '<>'
    let next = this.input.charCodeAt(this.pos + 1);
    let size = 1;

    if (next === code) {
      size = code === 62 && this.input.charCodeAt(this.pos + 2) === 62 ? 3 : 2;
      if (this.input.charCodeAt(this.pos + size) === 61) return this.finishOp(tt.assign, size + 1);
      return this.finishOp(tt.bitShift, size);
    }

    if (next === 33 && code === 60 && this.input.charCodeAt(this.pos + 2) === 45 && this.input.charCodeAt(this.pos + 3) === 45) {
      if (this.inModule) this.unexpected();
      // `<!--`, an XML-style comment that should be interpreted as a line comment
      this.skipLineComment(4);
      this.skipSpace();
      return this.nextToken();
    }

    if (next === 61) {
      size = this.input.charCodeAt(this.pos + 2) === 61 ? 3 : 2;
    }

    return this.finishOp(tt.relational, size);
  }

  readToken_eq_excl(code) { // '=!'
    let next = this.input.charCodeAt(this.pos + 1);
    if (next === 61) return this.finishOp(tt.equality, this.input.charCodeAt(this.pos + 2) === 61 ? 3 : 2);
    if (code === 61 && next === 62) { // '=>'
      this.pos += 2;
      return this.finishToken(tt.arrow);
    }
    return this.finishOp(code === 61 ? tt.eq : tt.prefix, 1);
  }

  getTokenFromCode(code) {
    switch (code) {
      // The interpretation of a dot depends on whether it is followed
      // by a digit or another two dots.
      case 46: // '.'
        return this.readToken_dot();

      // Punctuation tokens.
      case 40: ++this.pos; return this.finishToken(tt.parenL);
      case 41: ++this.pos; return this.finishToken(tt.parenR);
      case 59: ++this.pos; return this.finishToken(tt.semi);
      case 44: ++this.pos; return this.finishToken(tt.comma);
      case 91: ++this.pos; return this.finishToken(tt.bracketL);
      case 93: ++this.pos; return this.finishToken(tt.bracketR);
      case 123: ++this.pos; return this.finishToken(tt.braceL);
      case 125: ++this.pos; return this.finishToken(tt.braceR);

      case 58:
        if (this.options.features["es7.functionBind"] && this.input.charCodeAt(this.pos + 1) === 58) {
          return this.finishOp(tt.doubleColon, 2);
        } else {
          ++this.pos;
          return this.finishToken(tt.colon);
        }

      case 63: ++this.pos; return this.finishToken(tt.question);
      case 64: ++this.pos; return this.finishToken(tt.at);

      case 96: // '`'
        ++this.pos;
        return this.finishToken(tt.backQuote);

      case 48: // '0'
        let next = this.input.charCodeAt(this.pos + 1);
        if (next === 120 || next === 88) return this.readRadixNumber(16); // '0x', '0X' - hex number
        if (next === 111 || next === 79) return this.readRadixNumber(8); // '0o', '0O' - octal number
        if (next === 98 || next === 66) return this.readRadixNumber(2); // '0b', '0B' - binary number
        // Anything else beginning with a digit is an integer, octal
        // number, or float.
      case 49: case 50: case 51: case 52: case 53: case 54: case 55: case 56: case 57: // 1-9
        return this.readNumber(false);

        // Quotes produce strings.
      case 34: case 39: // '"', "'"
        return this.readString(code);

      // Operators are parsed inline in tiny state machines. '=' (61) is
      // often referred to. `finishOp` simply skips the amount of
      // characters it is given as second argument, and returns a token
      // of the type given by its first argument.

      case 47: // '/'
        return this.readToken_slash();

      case 37: case 42: // '%*'
        return this.readToken_mult_modulo(code);

      case 124: case 38: // '|&'
        return this.readToken_pipe_amp(code);

      case 94: // '^'
        return this.readToken_caret();

      case 43: case 45: // '+-'
        return this.readToken_plus_min(code);

      case 60: case 62: // '<>'
        return this.readToken_lt_gt(code);

      case 61: case 33: // '=!'
        return this.readToken_eq_excl(code);

      case 126: // '~'
        return this.finishOp(tt.prefix, 1);
    }

    this.raise(this.pos, `Unexpected character '${codePointToString(code)}'`);
  }

  finishOp(type, size) {
    let str = this.input.slice(this.pos, this.pos + size);
    this.pos += size;
    return this.finishToken(type, str);
  }

  readRegexp() {
    let escaped, inClass, start = this.pos;
    for (;;) {
      if (this.pos >= this.input.length) this.raise(start, "Unterminated regular expression");
      let ch = this.input.charAt(this.pos);
      if (lineBreak.test(ch)) this.raise(start, "Unterminated regular expression");
      if (escaped) {
        escaped = false;
      } else {
        if (ch === "[") inClass = true;
        else if (ch === "]" && inClass) inClass = false;
        else if (ch === "/" && !inClass) break;
        escaped = ch === "\\";
      }
      ++this.pos;
    }
    let content = this.input.slice(start, this.pos);
    ++this.pos;
    // Need to use `readWord1` because '\uXXXX' sequences are allowed
    // here (don't ask).
    let mods = this.readWord1();
    let tmp = content;
    if (mods) {
      let validFlags = /^[gmsiyu]*$/;
      if (!validFlags.test(mods)) this.raise(start, "Invalid regular expression flag");
      if (mods.indexOf("u") >= 0 && !regexpUnicodeSupport) {
        // Replace each astral symbol and every Unicode escape sequence that
        // possibly represents an astral symbol or a paired surrogate with a
        // single ASCII symbol to avoid throwing on regular expressions that
        // are only valid in combination with the `/u` flag.
        // Note: replacing with the ASCII symbol `x` might cause false
        // negatives in unlikely scenarios. For example, `[\u{61}-b]` is a
        // perfectly valid pattern that is equivalent to `[a-b]`, but it would
        // be replaced by `[x-b]` which throws an error.
        tmp = tmp.replace(/\\u\{([0-9a-fA-F]+)\}/g, (match, code, offset) => {
          code = Number("0x" + code);
          if (code > 0x10FFFF) this.raise(start + offset + 3, "Code point out of bounds");
          return "x";
        });
        tmp = tmp.replace(/\\u([a-fA-F0-9]{4})|[\uD800-\uDBFF][\uDC00-\uDFFF]/g, "x");
      }
    }
    // Detect invalid regular expressions.
    let value = null;
    // Rhino's regular expression parser is flaky and throws uncatchable exceptions,
    // so don't do detection if we are running under Rhino
    if (!isRhino) {
      tryCreateRegexp.call(this, tmp, undefined, start);
      // Get a regular expression object for this pattern-flag pair, or `null` in
      // case the current environment doesn't support the flags it uses.
      value = tryCreateRegexp.call(this, content, mods);
    }
    return this.finishToken(tt.regexp, {pattern: content, flags: mods, value: value});
  }

  // Read an integer in the given radix. Return null if zero digits
  // were read, the integer value otherwise. When `len` is given, this
  // will return `null` unless the integer has exactly `len` digits.

  readInt(radix, len) {
    let start = this.pos, total = 0;
    for (let i = 0, e = len == null ? Infinity : len; i < e; ++i) {
      let code = this.input.charCodeAt(this.pos), val;
      if (code >= 97) val = code - 97 + 10; // a
      else if (code >= 65) val = code - 65 + 10; // A
      else if (code >= 48 && code <= 57) val = code - 48; // 0-9
      else val = Infinity;
      if (val >= radix) break;
      ++this.pos;
      total = total * radix + val;
    }
    if (this.pos === start || len != null && this.pos - start !== len) return null;

    return total;
  }

  readRadixNumber(radix) {
    this.pos += 2; // 0x
    let val = this.readInt(radix);
    if (val == null) this.raise(this.start + 2, "Expected number in radix " + radix);
    if (isIdentifierStart(this.fullCharCodeAtPos())) this.raise(this.pos, "Identifier directly after number");
    return this.finishToken(tt.num, val);
  }

  // Read an integer, octal integer, or floating-point number.

  readNumber(startsWithDot) {
    let start = this.pos, isFloat = false, octal = this.input.charCodeAt(this.pos) === 48;
    if (!startsWithDot && this.readInt(10) === null) this.raise(start, "Invalid number");
    let next = this.input.charCodeAt(this.pos);
    if (next === 46) { // '.'
      ++this.pos;
      this.readInt(10);
      isFloat = true;
      next = this.input.charCodeAt(this.pos);
    }
    if (next === 69 || next === 101) { // 'eE'
      next = this.input.charCodeAt(++this.pos);
      if (next === 43 || next === 45) ++this.pos; // '+-'
      if (this.readInt(10) === null) this.raise(start, "Invalid number");
      isFloat = true;
    }
    if (isIdentifierStart(this.fullCharCodeAtPos())) this.raise(this.pos, "Identifier directly after number");

    let str = this.input.slice(start, this.pos), val;
    if (isFloat) val = parseFloat(str);
    else if (!octal || str.length === 1) val = parseInt(str, 10);
    else if (/[89]/.test(str) || this.strict) this.raise(start, "Invalid number");
    else val = parseInt(str, 8);
    return this.finishToken(tt.num, val);
  }

  // Read a string value, interpreting backslash-escapes.

  readCodePoint() {
    let ch = this.input.charCodeAt(this.pos), code;

    if (ch === 123) {
      let codePos = ++this.pos;
      code = this.readHexChar(this.input.indexOf("}", this.pos) - this.pos);
      ++this.pos;
      if (code > 0x10FFFF) this.raise(codePos, "Code point out of bounds");
    } else {
      code = this.readHexChar(4);
    }
    return code;
  }

  readString(quote) {
    let out = "", chunkStart = ++this.pos;
    for (;;) {
      if (this.pos >= this.input.length) this.raise(this.start, "Unterminated string constant");
      let ch = this.input.charCodeAt(this.pos);
      if (ch === quote) break;
      if (ch === 92) { // '\'
        out += this.input.slice(chunkStart, this.pos);
        out += this.readEscapedChar(false);
        chunkStart = this.pos;
      } else {
        if (isNewLine(ch)) this.raise(this.start, "Unterminated string constant");
        ++this.pos;
      }
    }
    out += this.input.slice(chunkStart, this.pos++);
    return this.finishToken(tt.string, out);
  }

  // Reads template string tokens.

  readTmplToken() {
    let out = "", chunkStart = this.pos;
    for (;;) {
      if (this.pos >= this.input.length) this.raise(this.start, "Unterminated template");
      let ch = this.input.charCodeAt(this.pos);
      if (ch === 96 || ch === 36 && this.input.charCodeAt(this.pos + 1) === 123) { // '`', '${'
        if (this.pos === this.start && this.type === tt.template) {
          if (ch === 36) {
            this.pos += 2;
            return this.finishToken(tt.dollarBraceL);
          } else {
            ++this.pos;
            return this.finishToken(tt.backQuote);
          }
        }
        out += this.input.slice(chunkStart, this.pos);
        return this.finishToken(tt.template, out);
      }
      if (ch === 92) { // '\'
        out += this.input.slice(chunkStart, this.pos);
        out += this.readEscapedChar(true);
        chunkStart = this.pos;
      } else if (isNewLine(ch)) {
        out += this.input.slice(chunkStart, this.pos);
        ++this.pos;
        switch (ch) {
          case 13:
            if (this.input.charCodeAt(this.pos) === 10) ++this.pos;
          case 10:
            out += "\n";
            break;
          default:
            out += String.fromCharCode(ch);
            break;
        }
        ++this.curLine;
        this.lineStart = this.pos;
        chunkStart = this.pos;
      } else {
        ++this.pos;
      }
    }
  }

  // Used to read escaped characters

  readEscapedChar(inTemplate) {
    let ch = this.input.charCodeAt(++this.pos);
    ++this.pos;
    switch (ch) {
      case 110: return "\n"; // 'n' -> '\n'
      case 114: return "\r"; // 'r' -> '\r'
      case 120: return String.fromCharCode(this.readHexChar(2)); // 'x'
      case 117: return codePointToString(this.readCodePoint()); // 'u'
      case 116: return "\t"; // 't' -> '\t'
      case 98: return "\b"; // 'b' -> '\b'
      case 118: return "\u000b"; // 'v' -> '\u000b'
      case 102: return "\f"; // 'f' -> '\f'
      case 13: if (this.input.charCodeAt(this.pos) === 10) ++this.pos; // '\r\n'
      case 10: // ' \n'
        this.lineStart = this.pos;
        ++this.curLine;
        return "";
      default:
        if (ch >= 48 && ch <= 55) {
          let octalStr = this.input.substr(this.pos - 1, 3).match(/^[0-7]+/)[0];
          let octal = parseInt(octalStr, 8);
          if (octal > 255) {
            octalStr = octalStr.slice(0, -1);
            octal = parseInt(octalStr, 8);
          }
          if (octal > 0 && (this.strict || inTemplate)) {
            this.raise(this.pos - 2, "Octal literal in strict mode");
          }
          this.pos += octalStr.length - 1;
          return String.fromCharCode(octal);
        }
        return String.fromCharCode(ch);
    }
  }

  // Used to read character escape sequences ('\x', '\u', '\U').

  readHexChar(len) {
    let codePos = this.pos;
    let n = this.readInt(16, len);
    if (n === null) this.raise(codePos, "Bad character escape sequence");
    return n;
  }

  // Read an identifier, and return it as a string. Sets `containsEsc`
  // to whether the word contained a '\u' escape.
  //
  // Incrementally adds only escaped chars, adding other chunks as-is
  // as a micro-optimization.

  readWord1() {
    containsEsc = false;
    let word = "", first = true, chunkStart = this.pos;
    while (this.pos < this.input.length) {
      let ch = this.fullCharCodeAtPos();
      if (isIdentifierChar(ch, true)) {
        this.pos += ch <= 0xffff ? 1 : 2;
      } else if (ch === 92) { // "\"
        containsEsc = true;

        word += this.input.slice(chunkStart, this.pos);
        let escStart = this.pos;

        if (this.input.charCodeAt(++this.pos) !== 117) { // "u"
          this.raise(this.pos, "Expecting Unicode escape sequence \\uXXXX");
        }

        ++this.pos;
        let esc = this.readCodePoint();
        if (!(first ? isIdentifierStart : isIdentifierChar)(esc, true)) {
          this.raise(escStart, "Invalid Unicode escape");
        }

        word += codePointToString(esc);
        chunkStart = this.pos;
      } else {
        break;
      }
      first = false;
    }
    return word + this.input.slice(chunkStart, this.pos);
  }

  // Read an identifier or keyword token. Will check for reserved
  // words when necessary.

  readWord() {
    let word = this.readWord1();
    let type = tt.name;
    if (!containsEsc && this.isKeyword(word))
      type = keywordTypes[word];
    return this.finishToken(type, word);
  }
}