import PatternParser from './AsYouTypeFormatter.PatternParser.js';
export default class PatternMatcher {
  constructor(pattern) {
    this.matchTree = new PatternParser().parse(pattern);
  }
  match(string, {
    allowOverflow
  } = {}) {
    if (!string) {
      throw new Error('String is required');
    }
    const result = match(string.split(''), this.matchTree, true);
    if (result && result.match) {
      delete result.matchedChars;
    }
    if (result && result.overflow) {
      if (!allowOverflow) {
        return;
      }
    }
    return result;
  }
}

/**
 * Matches `characters` against a pattern compiled into a `tree`.
 * @param  {string[]} characters
 * @param  {Tree} tree — A pattern compiled into a `tree`. See the `*.d.ts` file for the description of the `tree` structure.
 * @param  {boolean} last — Whether it's the last (rightmost) subtree on its level of the match tree.
 * @return {object} See the `*.d.ts` file for the description of the result object.
 */
function match(characters, tree, last) {
  // If `tree` is a string, then `tree` is a single character.
  // That's because when a pattern is parsed, multi-character-string parts
  // of a pattern are compiled into arrays of single characters.
  // I still wrote this piece of code for a "general" hypothetical case
  // when `tree` could be a string of several characters, even though
  // such case is not possible with the current implementation.
  if (typeof tree === 'string') {
    const characterString = characters.join('');
    if (tree.indexOf(characterString) === 0) {
      // `tree` is always a single character.
      // If `tree.indexOf(characterString) === 0`
      // then `characters.length === tree.length`.
      /* istanbul ignore else */
      if (characters.length === tree.length) {
        return {
          match: true,
          matchedChars: characters
        };
      }
      // `tree` is always a single character.
      // If `tree.indexOf(characterString) === 0`
      // then `characters.length === tree.length`.
      /* istanbul ignore next */
      return {
        partialMatch: true
        // matchedChars: characters
      };
    }
    if (characterString.indexOf(tree) === 0) {
      if (last) {
        // The `else` path is not possible because `tree` is always a single character.
        // The `else` case for `characters.length > tree.length` would be
        // `characters.length <= tree.length` which means `characters.length <= 1`.
        // `characters` array can't be empty, so that means `characters === [tree]`,
        // which would also mean `tree.indexOf(characterString) === 0` and that'd mean
        // that the `if (tree.indexOf(characterString) === 0)` condition before this
        // `if` condition would be entered, and returned from there, not reaching this code.
        /* istanbul ignore else */
        if (characters.length > tree.length) {
          return {
            overflow: true
          };
        }
      }
      return {
        match: true,
        matchedChars: characters.slice(0, tree.length)
      };
    }
    return;
  }
  if (Array.isArray(tree)) {
    let restCharacters = characters.slice();
    let i = 0;
    while (i < tree.length) {
      const subtree = tree[i];
      const result = match(restCharacters, subtree, last && i === tree.length - 1);
      if (!result) {
        return;
      } else if (result.overflow) {
        return result;
      } else if (result.match) {
        // Continue with the next subtree with the rest of the characters.
        restCharacters = restCharacters.slice(result.matchedChars.length);
        if (restCharacters.length === 0) {
          if (i === tree.length - 1) {
            return {
              match: true,
              matchedChars: characters
            };
          } else {
            return {
              partialMatch: true
              // matchedChars: characters
            };
          }
        }
      } else {
        /* istanbul ignore else */
        if (result.partialMatch) {
          return {
            partialMatch: true
            // matchedChars: characters
          };
        } else {
          throw new Error(`Unsupported match result:\n${JSON.stringify(result, null, 2)}`);
        }
      }
      i++;
    }
    // If `last` then overflow has already been checked
    // by the last element of the `tree` array.
    /* istanbul ignore if */
    if (last) {
      return {
        overflow: true
      };
    }
    return {
      match: true,
      matchedChars: characters.slice(0, characters.length - restCharacters.length)
    };
  }
  switch (tree.op) {
    case '|':
      let partialMatch;
      for (const branch of tree.args) {
        const result = match(characters, branch, last);
        if (result) {
          if (result.overflow) {
            return result;
          } else if (result.match) {
            return {
              match: true,
              matchedChars: result.matchedChars
            };
          } else {
            /* istanbul ignore else */
            if (result.partialMatch) {
              partialMatch = true;
            } else {
              throw new Error(`Unsupported match result:\n${JSON.stringify(result, null, 2)}`);
            }
          }
        }
      }
      if (partialMatch) {
        return {
          partialMatch: true
          // matchedChars: ...
        };
      }
      // Not even a partial match.
      return;
    case '[]':
      for (const char of tree.args) {
        if (characters[0] === char) {
          if (characters.length === 1) {
            return {
              match: true,
              matchedChars: characters
            };
          }
          if (last) {
            return {
              overflow: true
            };
          }
          return {
            match: true,
            matchedChars: [char]
          };
        }
      }
      // No character matches.
      return;

    /* istanbul ignore next */
    default:
      throw new Error(`Unsupported instruction tree: ${tree}`);
  }
}
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