var assert = require("assert");
var linesModule = require("./lines");
var types = require("./types");
var getFieldValue = types.getFieldValue;
var Node = types.namedTypes.Node;
var Printable = types.namedTypes.Printable;
var Expression = types.namedTypes.Expression;
var ReturnStatement = types.namedTypes.ReturnStatement;
var SourceLocation = types.namedTypes.SourceLocation;
var util = require("./util");
var comparePos = util.comparePos;
var FastPath = require("./fast-path");
var isObject = types.builtInTypes.object;
var isArray = types.builtInTypes.array;
var isString = types.builtInTypes.string;
var riskyAdjoiningCharExp = /[0-9a-z_$]/i;

function Patcher(lines) {
  assert.ok(this instanceof Patcher);
  assert.ok(lines instanceof linesModule.Lines);

  var self = this,
  replacements = [];

  self.replace = function(loc, lines) {
    if (isString.check(lines))
      lines = linesModule.fromString(lines);

    replacements.push({
      lines: lines,
      start: loc.start,
      end: loc.end
    });
  };

  self.get = function(loc) {
    // If no location is provided, return the complete Lines object.
    loc = loc || {
      start: { line: 1, column: 0 },
      end: { line: lines.length,
             column: lines.getLineLength(lines.length) }
    };

    var sliceFrom = loc.start,
    toConcat = [];

    function pushSlice(from, to) {
      assert.ok(comparePos(from, to) <= 0);
      toConcat.push(lines.slice(from, to));
    }

    replacements.sort(function(a, b) {
      return comparePos(a.start, b.start);
    }).forEach(function(rep) {
      if (comparePos(sliceFrom, rep.start) > 0) {
        // Ignore nested replacement ranges.
      } else {
        pushSlice(sliceFrom, rep.start);
        toConcat.push(rep.lines);
        sliceFrom = rep.end;
      }
    });

    pushSlice(sliceFrom, loc.end);

    return linesModule.concat(toConcat);
  };
}
exports.Patcher = Patcher;

var Pp = Patcher.prototype;

Pp.tryToReprintComments = function(newNode, oldNode, print) {
  var patcher = this;

  if (!newNode.comments &&
      !oldNode.comments) {
    // We were (vacuously) able to reprint all the comments!
    return true;
  }

  var newPath = FastPath.from(newNode);
  var oldPath = FastPath.from(oldNode);

  newPath.stack.push("comments", getSurroundingComments(newNode));
  oldPath.stack.push("comments", getSurroundingComments(oldNode));

  var reprints = [];
  var ableToReprintComments =
    findArrayReprints(newPath, oldPath, reprints);

  // No need to pop anything from newPath.stack or oldPath.stack, since
  // newPath and oldPath are fresh local variables.

  if (ableToReprintComments && reprints.length > 0) {
    reprints.forEach(function(reprint) {
      var oldComment = reprint.oldPath.getValue();
      assert.ok(oldComment.leading || oldComment.trailing);
      patcher.replace(
        oldComment.loc,
        // Comments can't have .comments, so it doesn't matter whether we
        // print with comments or without.
        print(reprint.newPath).indentTail(oldComment.loc.indent)
      );
    });
  }

  return ableToReprintComments;
};

// Get all comments that are either leading or trailing, ignoring any
// comments that occur inside node.loc. Returns an empty array for nodes
// with no leading or trailing comments.
function getSurroundingComments(node) {
  var result = [];
  if (node.comments &&
      node.comments.length > 0) {
    node.comments.forEach(function(comment) {
      if (comment.leading || comment.trailing) {
        result.push(comment);
      }
    });
  }
  return result;
}

Pp.deleteComments = function(node) {
  if (!node.comments) {
    return;
  }

  var patcher = this;

  node.comments.forEach(function(comment) {
    if (comment.leading) {
      // Delete leading comments along with any trailing whitespace they
      // might have.
      patcher.replace({
        start: comment.loc.start,
        end: node.loc.lines.skipSpaces(
          comment.loc.end, false, false)
      }, "");

    } else if (comment.trailing) {
      // Delete trailing comments along with any leading whitespace they
      // might have.
      patcher.replace({
        start: node.loc.lines.skipSpaces(
          comment.loc.start, true, false),
        end: comment.loc.end
      }, "");
    }
  });
};

exports.getReprinter = function(path) {
  assert.ok(path instanceof FastPath);

  // Make sure that this path refers specifically to a Node, rather than
  // some non-Node subproperty of a Node.
  var node = path.getValue();
  if (!Printable.check(node))
    return;

  var orig = node.original;
  var origLoc = orig && orig.loc;
  var lines = origLoc && origLoc.lines;
  var reprints = [];

  if (!lines || !findReprints(path, reprints))
    return;

  return function(print) {
    var patcher = new Patcher(lines);

    reprints.forEach(function(reprint) {
      var newNode = reprint.newPath.getValue();
      var oldNode = reprint.oldPath.getValue();

      SourceLocation.assert(oldNode.loc, true);

      var needToPrintNewPathWithComments =
        !patcher.tryToReprintComments(newNode, oldNode, print)

      if (needToPrintNewPathWithComments) {
        // Since we were not able to preserve all leading/trailing
        // comments, we delete oldNode's comments, print newPath with
        // comments, and then patch the resulting lines where oldNode used
        // to be.
        patcher.deleteComments(oldNode);
      }

      var newLines = print(reprint.newPath, {
        includeComments: needToPrintNewPathWithComments,
        // If the oldNode we're replacing already had parentheses, we may
        // not need to print the new node with any extra parentheses,
        // because the existing parentheses will suffice. However, if the
        // newNode has a different type than the oldNode, let the printer
        // decide if reprint.newPath needs parentheses, as usual.
        avoidRootParens: (oldNode.type === newNode.type &&
                          reprint.oldPath.hasParens())
      }).indentTail(oldNode.loc.indent);

      var nls = needsLeadingSpace(lines, oldNode.loc, newLines);
      var nts = needsTrailingSpace(lines, oldNode.loc, newLines);

      // If we try to replace the argument of a ReturnStatement like
      // return"asdf" with e.g. a literal null expression, we run the risk
      // of ending up with returnnull, so we need to add an extra leading
      // space in situations where that might happen. Likewise for
      // "asdf"in obj. See #170.
      if (nls || nts) {
        var newParts = [];
        nls && newParts.push(" ");
        newParts.push(newLines);
        nts && newParts.push(" ");
        newLines = linesModule.concat(newParts);
      }

      patcher.replace(oldNode.loc, newLines);
    });

    // Recall that origLoc is the .loc of an ancestor node that is
    // guaranteed to contain all the reprinted nodes and comments.
    const patchedLines = patcher.get(origLoc).indentTail(-orig.loc.indent);

    if (path.needsParens()) {
      return linesModule.concat(["(", patchedLines, ")"]);
    }

    return patchedLines;
  };
};

// If the last character before oldLoc and the first character of newLines
// are both identifier characters, they must be separated by a space,
// otherwise they will most likely get fused together into a single token.
function needsLeadingSpace(oldLines, oldLoc, newLines) {
  var posBeforeOldLoc = util.copyPos(oldLoc.start);

  // The character just before the location occupied by oldNode.
  var charBeforeOldLoc =
    oldLines.prevPos(posBeforeOldLoc) &&
    oldLines.charAt(posBeforeOldLoc);

  // First character of the reprinted node.
  var newFirstChar = newLines.charAt(newLines.firstPos());

  return charBeforeOldLoc &&
    riskyAdjoiningCharExp.test(charBeforeOldLoc) &&
    newFirstChar &&
    riskyAdjoiningCharExp.test(newFirstChar);
}

// If the last character of newLines and the first character after oldLoc
// are both identifier characters, they must be separated by a space,
// otherwise they will most likely get fused together into a single token.
function needsTrailingSpace(oldLines, oldLoc, newLines) {
  // The character just after the location occupied by oldNode.
  var charAfterOldLoc = oldLines.charAt(oldLoc.end);

  var newLastPos = newLines.lastPos();

  // Last character of the reprinted node.
  var newLastChar = newLines.prevPos(newLastPos) &&
    newLines.charAt(newLastPos);

  return newLastChar &&
    riskyAdjoiningCharExp.test(newLastChar) &&
    charAfterOldLoc &&
    riskyAdjoiningCharExp.test(charAfterOldLoc);
}

function findReprints(newPath, reprints) {
  var newNode = newPath.getValue();
  Printable.assert(newNode);

  var oldNode = newNode.original;
  Printable.assert(oldNode);

  assert.deepEqual(reprints, []);

  if (newNode.type !== oldNode.type) {
    return false;
  }

  var oldPath = new FastPath(oldNode);
  var canReprint = findChildReprints(newPath, oldPath, reprints);

  if (!canReprint) {
    // Make absolutely sure the calling code does not attempt to reprint
    // any nodes.
    reprints.length = 0;
  }

  return canReprint;
}

function findAnyReprints(newPath, oldPath, reprints) {
  var newNode = newPath.getValue();
  var oldNode = oldPath.getValue();

  if (newNode === oldNode)
    return true;

  if (isArray.check(newNode))
    return findArrayReprints(newPath, oldPath, reprints);

  if (isObject.check(newNode))
    return findObjectReprints(newPath, oldPath, reprints);

  return false;
}

function findArrayReprints(newPath, oldPath, reprints) {
  var newNode = newPath.getValue();
  var oldNode = oldPath.getValue();

  if (newNode === oldNode ||
      newPath.valueIsDuplicate() ||
      oldPath.valueIsDuplicate()) {
    return true;
  }

  isArray.assert(newNode);
  var len = newNode.length;

  if (!(isArray.check(oldNode) &&
        oldNode.length === len))
    return false;

  for (var i = 0; i < len; ++i) {
    newPath.stack.push(i, newNode[i]);
    oldPath.stack.push(i, oldNode[i]);
    var canReprint = findAnyReprints(newPath, oldPath, reprints);
    newPath.stack.length -= 2;
    oldPath.stack.length -= 2;
    if (!canReprint) {
      return false;
    }
  }

  return true;
}

function findObjectReprints(newPath, oldPath, reprints) {
  var newNode = newPath.getValue();
  isObject.assert(newNode);

  if (newNode.original === null) {
    // If newNode.original node was set to null, reprint the node.
    return false;
  }

  var oldNode = oldPath.getValue();
  if (!isObject.check(oldNode))
    return false;

  if (newNode === oldNode ||
      newPath.valueIsDuplicate() ||
      oldPath.valueIsDuplicate()) {
    return true;
  }

  if (Printable.check(newNode)) {
    if (!Printable.check(oldNode)) {
      return false;
    }

    // Here we need to decide whether the reprinted code for newNode is
    // appropriate for patching into the location of oldNode.

    if (newNode.type === oldNode.type) {
      var childReprints = [];

      if (findChildReprints(newPath, oldPath, childReprints)) {
        reprints.push.apply(reprints, childReprints);
      } else if (oldNode.loc) {
        // If we have no .loc information for oldNode, then we won't be
        // able to reprint it.
        reprints.push({
          oldPath: oldPath.copy(),
          newPath: newPath.copy()
        });
      } else {
        return false;
      }

      return true;
    }

    if (Expression.check(newNode) &&
        Expression.check(oldNode) &&
        // If we have no .loc information for oldNode, then we won't be
        // able to reprint it.
        oldNode.loc) {

      // If both nodes are subtypes of Expression, then we should be able
      // to fill the location occupied by the old node with code printed
      // for the new node with no ill consequences.
      reprints.push({
        oldPath: oldPath.copy(),
        newPath: newPath.copy()
      });

      return true;
    }

    // The nodes have different types, and at least one of the types is
    // not a subtype of the Expression type, so we cannot safely assume
    // the nodes are syntactically interchangeable.
    return false;
  }

  return findChildReprints(newPath, oldPath, reprints);
}

function findChildReprints(newPath, oldPath, reprints) {
  var newNode = newPath.getValue();
  var oldNode = oldPath.getValue();

  isObject.assert(newNode);
  isObject.assert(oldNode);

  if (newNode.original === null) {
    // If newNode.original node was set to null, reprint the node.
    return false;
  }

  // If this node needs parentheses and will not be wrapped with
  // parentheses when reprinted, then return false to skip reprinting and
  // let it be printed generically.
  if (newPath.needsParens() &&
      ! oldPath.hasParens()) {
    return false;
  }

  var keys = util.getUnionOfKeys(oldNode, newNode);

  if (oldNode.type === "File" ||
      newNode.type === "File") {
    // Don't bother traversing file.tokens, an often very large array
    // returned by Babylon, and useless for our purposes.
    delete keys.tokens;
  }

  // Don't bother traversing .loc objects looking for reprintable nodes.
  delete keys.loc;

  var originalReprintCount = reprints.length;

  for (var k in keys) {
    if (k.charAt(0) === "_") {
      // Ignore "private" AST properties added by e.g. Babel plugins and
      // parsers like Babylon.
      continue;
    }

    newPath.stack.push(k, types.getFieldValue(newNode, k));
    oldPath.stack.push(k, types.getFieldValue(oldNode, k));
    var canReprint = findAnyReprints(newPath, oldPath, reprints);
    newPath.stack.length -= 2;
    oldPath.stack.length -= 2;

    if (!canReprint) {
      return false;
    }
  }

  // Return statements might end up running into ASI issues due to
  // comments inserted deep within the tree, so reprint them if anything
  // changed within them.
  if (ReturnStatement.check(newPath.getNode()) &&
      reprints.length > originalReprintCount) {
    return false;
  }

  return true;
}
