'use strict';

var URI = require('uri-js')
  , equal = require('fast-deep-equal')
  , util = require('./util')
  , SchemaObject = require('./schema_obj')
  , traverse = require('json-schema-traverse');

module.exports = resolve;

resolve.normalizeId = normalizeId;
resolve.fullPath = getFullPath;
resolve.url = resolveUrl;
resolve.ids = resolveIds;
resolve.inlineRef = inlineRef;
resolve.schema = resolveSchema;

/**
 * [resolve and compile the references ($ref)]
 * @this   Ajv
 * @param  {Function} compile reference to schema compilation funciton (localCompile)
 * @param  {Object} root object with information about the root schema for the current schema
 * @param  {String} ref reference to resolve
 * @return {Object|Function} schema object (if the schema can be inlined) or validation function
 */
function resolve(compile, root, ref) {
  /* jshint validthis: true */
  var refVal = this._refs[ref];
  if (typeof refVal == 'string') {
    if (this._refs[refVal]) refVal = this._refs[refVal];
    else return resolve.call(this, compile, root, refVal);
  }

  refVal = refVal || this._schemas[ref];
  if (refVal instanceof SchemaObject) {
    return inlineRef(refVal.schema, this._opts.inlineRefs)
            ? refVal.schema
            : refVal.validate || this._compile(refVal);
  }

  var res = resolveSchema.call(this, root, ref);
  var schema, v, baseId;
  if (res) {
    schema = res.schema;
    root = res.root;
    baseId = res.baseId;
  }

  if (schema instanceof SchemaObject) {
    v = schema.validate || compile.call(this, schema.schema, root, undefined, baseId);
  } else if (schema !== undefined) {
    v = inlineRef(schema, this._opts.inlineRefs)
        ? schema
        : compile.call(this, schema, root, undefined, baseId);
  }

  return v;
}


/**
 * Resolve schema, its root and baseId
 * @this Ajv
 * @param  {Object} root root object with properties schema, refVal, refs
 * @param  {String} ref  reference to resolve
 * @return {Object} object with properties schema, root, baseId
 */
function resolveSchema(root, ref) {
  /* jshint validthis: true */
  var p = URI.parse(ref)
    , refPath = _getFullPath(p)
    , baseId = getFullPath(this._getId(root.schema));
  if (Object.keys(root.schema).length === 0 || refPath !== baseId) {
    var id = normalizeId(refPath);
    var refVal = this._refs[id];
    if (typeof refVal == 'string') {
      return resolveRecursive.call(this, root, refVal, p);
    } else if (refVal instanceof SchemaObject) {
      if (!refVal.validate) this._compile(refVal);
      root = refVal;
    } else {
      refVal = this._schemas[id];
      if (refVal instanceof SchemaObject) {
        if (!refVal.validate) this._compile(refVal);
        if (id == normalizeId(ref))
          return { schema: refVal, root: root, baseId: baseId };
        root = refVal;
      } else {
        return;
      }
    }
    if (!root.schema) return;
    baseId = getFullPath(this._getId(root.schema));
  }
  return getJsonPointer.call(this, p, baseId, root.schema, root);
}


/* @this Ajv */
function resolveRecursive(root, ref, parsedRef) {
  /* jshint validthis: true */
  var res = resolveSchema.call(this, root, ref);
  if (res) {
    var schema = res.schema;
    var baseId = res.baseId;
    root = res.root;
    var id = this._getId(schema);
    if (id) baseId = resolveUrl(baseId, id);
    return getJsonPointer.call(this, parsedRef, baseId, schema, root);
  }
}


var PREVENT_SCOPE_CHANGE = util.toHash(['properties', 'patternProperties', 'enum', 'dependencies', 'definitions']);
/* @this Ajv */
function getJsonPointer(parsedRef, baseId, schema, root) {
  /* jshint validthis: true */
  parsedRef.fragment = parsedRef.fragment || '';
  if (parsedRef.fragment.slice(0,1) != '/') return;
  var parts = parsedRef.fragment.split('/');

  for (var i = 1; i < parts.length; i++) {
    var part = parts[i];
    if (part) {
      part = util.unescapeFragment(part);
      schema = schema[part];
      if (schema === undefined) break;
      var id;
      if (!PREVENT_SCOPE_CHANGE[part]) {
        id = this._getId(schema);
        if (id) baseId = resolveUrl(baseId, id);
        if (schema.$ref) {
          var $ref = resolveUrl(baseId, schema.$ref);
          var res = resolveSchema.call(this, root, $ref);
          if (res) {
            schema = res.schema;
            root = res.root;
            baseId = res.baseId;
          }
        }
      }
    }
  }
  if (schema !== undefined && schema !== root.schema)
    return { schema: schema, root: root, baseId: baseId };
}


var SIMPLE_INLINED = util.toHash([
  'type', 'format', 'pattern',
  'maxLength', 'minLength',
  'maxProperties', 'minProperties',
  'maxItems', 'minItems',
  'maximum', 'minimum',
  'uniqueItems', 'multipleOf',
  'required', 'enum'
]);
function inlineRef(schema, limit) {
  if (limit === false) return false;
  if (limit === undefined || limit === true) return checkNoRef(schema);
  else if (limit) return countKeys(schema) <= limit;
}


function checkNoRef(schema) {
  var item;
  if (Array.isArray(schema)) {
    for (var i=0; i<schema.length; i++) {
      item = schema[i];
      if (typeof item == 'object' && !checkNoRef(item)) return false;
    }
  } else {
    for (var key in schema) {
      if (key == '$ref') return false;
      item = schema[key];
      if (typeof item == 'object' && !checkNoRef(item)) return false;
    }
  }
  return true;
}


function countKeys(schema) {
  var count = 0, item;
  if (Array.isArray(schema)) {
    for (var i=0; i<schema.length; i++) {
      item = schema[i];
      if (typeof item == 'object') count += countKeys(item);
      if (count == Infinity) return Infinity;
    }
  } else {
    for (var key in schema) {
      if (key == '$ref') return Infinity;
      if (SIMPLE_INLINED[key]) {
        count++;
      } else {
        item = schema[key];
        if (typeof item == 'object') count += countKeys(item) + 1;
        if (count == Infinity) return Infinity;
      }
    }
  }
  return count;
}


function getFullPath(id, normalize) {
  if (normalize !== false) id = normalizeId(id);
  var p = URI.parse(id);
  return _getFullPath(p);
}


function _getFullPath(p) {
  return URI.serialize(p).split('#')[0] + '#';
}


var TRAILING_SLASH_HASH = /#\/?$/;
function normalizeId(id) {
  return id ? id.replace(TRAILING_SLASH_HASH, '') : '';
}


function resolveUrl(baseId, id) {
  id = normalizeId(id);
  return URI.resolve(baseId, id);
}


/* @this Ajv */
function resolveIds(schema) {
  var schemaId = normalizeId(this._getId(schema));
  var baseIds = {'': schemaId};
  var fullPaths = {'': getFullPath(schemaId, false)};
  var localRefs = {};
  var self = this;

  traverse(schema, {allKeys: true}, function(sch, jsonPtr, rootSchema, parentJsonPtr, parentKeyword, parentSchema, keyIndex) {
    if (jsonPtr === '') return;
    var id = self._getId(sch);
    var baseId = baseIds[parentJsonPtr];
    var fullPath = fullPaths[parentJsonPtr] + '/' + parentKeyword;
    if (keyIndex !== undefined)
      fullPath += '/' + (typeof keyIndex == 'number' ? keyIndex : util.escapeFragment(keyIndex));

    if (typeof id == 'string') {
      id = baseId = normalizeId(baseId ? URI.resolve(baseId, id) : id);

      var refVal = self._refs[id];
      if (typeof refVal == 'string') refVal = self._refs[refVal];
      if (refVal && refVal.schema) {
        if (!equal(sch, refVal.schema))
          throw new Error('id "' + id + '" resolves to more than one schema');
      } else if (id != normalizeId(fullPath)) {
        if (id[0] == '#') {
          if (localRefs[id] && !equal(sch, localRefs[id]))
            throw new Error('id "' + id + '" resolves to more than one schema');
          localRefs[id] = sch;
        } else {
          self._refs[id] = fullPath;
        }
      }
    }
    baseIds[jsonPtr] = baseId;
    fullPaths[jsonPtr] = fullPath;
  });

  return localRefs;
}