import fetchDocByRef from '/imports/api/creature/parenting/fetchDocByRef.js';
import getCollectionByName from '/imports/api/creature/parenting/getCollectionByName.js';
import SimpleSchema from 'simpl-schema';

// n = collections.length
let collections = [];

export function registerCollection(collectionName){
  collections.push(collectionName);
}

// 1 database hit to get the parent by reference
export function fetchParent({id, collection}){
  return fetchDocByRef({id, collection});
}

// n database hits to get the children by parent id
export function fetchChildren({parentId, filter = {}, options}){
  filter["parent.id"] = parentId;
  let children = [];
  collections.forEach(collection => {
    children.push(
      ...collection.find({
        "parent.id": parentId
      }, options).fetch()
    );
  });
  return children;
}

// n database hits to update the decendents
export function updateChildren({parentId, filter = {}, modifier, options={}}){
  filter["parent.id"] = parentId;
  options.multi = true;
  collections.forEach(collection => {
    collection.update(filter, modifier, options);
  });
}

// n database hits to fetch the decendents by ancestor id, in no particular order
export function fetchDecendents({ancestorId, filter = {}, options}){
  filter["ancestors.id"] = ancestorId;
  let decendents = [];
  collections.forEach(collection => {
    decendents.push(...collection.find(filter, options).fetch());
  });
  return decendents;
}

// n database hits to update the decendents
export function updateDecendents({ancestorId, filter = {}, modifier, options={}}){
  filter["ancestors.id"] = ancestorId;
  options.multi = true;
  collections.forEach(collection => {
    collection.update(filter, modifier, options);
  });
}

// n database hits to get decendents to act on
export function forEachDecendent({ancestorId, filter = {}, options}, callback){
  filter["ancestors.id"] = ancestorId;
  collections.forEach(collection => {
    collection.find(filter, options).forEach(callback);
  });
}

// 1 database read
// TODO generalise for all inheritedFields
export function getAncestry({id, collection}){
  // Get the parent ref
  let parentDoc = fetchDocByRef({id, collection}, {fields: {
    name: 1,
    enabled: 1,
    ancestors: 1,
  }});
  let parent = {
    id,
    collection,
    name: parentDoc.name,
    enabled: parentDoc.enabled,
  };

  // Ancestors is [...parent's ancestors, parent ref]
  let ancestors = parentDoc.ancestors || [];
  ancestors.push(parent);

  return {parent, ancestors};
}

export function setDocAncestryMixin(methodOptions){
  // Extend the method's schema to require the needed properties
  // This mixin should come before simpleschema mixin
  methodOptions.schema = new SimpleSchema({
    parent: {
      type: Object,
      optional: true,
    },
    'parent.id': {
      type: String,
      regEx: SimpleSchema.RegEx.Id,
    },
    'parent.collection': {
      type: String,
    },
  }).extend(methodOptions.schema);
  // Change the doc's ancestry before running
  let runFunc = methodOptions.run;
  methodOptions.run = function(doc, ...rest){
    // If the doc's parent doesn't exist, set it to the character
    if (!doc.parent && doc.charId) {
      doc.parent = {id: doc.charId, collection: 'creatures'};
    }
    let {parent, ancestors} = getAncestry(doc.parent);
    doc.parent = parent;
    doc.ancestors = ancestors;
    return runFunc.call(this, doc, ...rest);
  };
  return methodOptions;
}

function ensureAncestryContainsId(ancestors, id){
  if (!id){
    throw new Meteor.Error('ancestor-check-failed',
      `Expected charId, got ${id}`
    );
  }
  if (!ancestors){
    throw new Meteor.Error('ancestor-check-failed',
      `Expected ancestors array, got ${ancestors}`
    );
  }
  for (let ancestor of ancestors){
    if (ancestor.id === id){
      return;
    }
  }
  throw new Meteor.Error('ancestor-check-failed',
    `Ancestors did not contain id: ${id}`
  );
}

export function ensureAncestryContainsCharIdMixin(methodOptions){
  // Extend the method's schema to require the needed properties
  // This mixin should come before simpleSchemaMixin
  methodOptions.schema = new SimpleSchema({
    charId: {
      type: String,
      regEx: SimpleSchema.RegEx.Id,
    },
  }).extend(methodOptions.schema);
  let runFunc = methodOptions.run;
  methodOptions.run = function({charId, ancestors}){
    ensureAncestryContainsId(ancestors, charId);
    return runFunc.apply(this, arguments);
  };
  return methodOptions;
}


export function updateParent(docRef, parentRef){
  let collection = getCollectionByName(docRef.collection);
  let oldDoc = fetchDocByRef(docRef, {fields: {
    parent: 1,
    ancestors: 1,
  }});

  // Skip if we aren't changing the parent id
  if (oldDoc.parent.id === parentRef.id) return;

  // update the document's parenting
  let {parent, ancestors} = getAncestry(parentRef);
  collection.update(docRef.id, {$set: {parent, ancestors}});

  // Remove the old ancestors from the decendents
  updateDecendents({
    ancestorId: docRef.id,
    modifier: {$pullAll: {
      ancestors: oldDoc.ancestors,
    }},
  });

  // Add the new ancestors to the decendents
  updateDecendents({
    ancestorId: docRef.id,
    modifier: {$push: {
      ancestors: {
        $each: ancestors,
        $position: 0,
      },
    }},
  });
}

// TODO these rely on hard coding inherited fields
// the inherited fields should only appear on the childChema, nowhere else
// Move these somewhere appropriate
export function findEnabled(collection, query, options){
  query.enabled = true;
  query['ancestors.$.enabled'] = {$not: false};
  return collection.find(query, options);
}

export function getName(doc){
  if (doc.name) return name;
  var i = doc.ancestors.length;
  while(i--) {
    if (ancestors[i].name) return ancestors[i].name;
  }
}