/*
 * Copyright (C) 2019 StApps
 * This program is free software: you can redistribute it and/or modify it
 * under the terms of the GNU General Public License as published by the Free
 * Software Foundation, version 3.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for
 * more details.
 *
 * You should have received a copy of the GNU General Public License along with
 * this program. If not, see <https://www.gnu.org/licenses/>.
 */
import {Logger} from '@openstapps/logger';
import * as deepmerge from 'deepmerge';
import {stringify} from 'flatted';
import {DeclarationReflection, ProjectReflection} from 'typedoc';
import {
  ArrayType,
  Comment,
  CommentTag,
  IntrinsicType,
  ReferenceType,
  ReflectionType,
  StringLiteralType,
  Type,
  TypeParameterType,
  UnionType,
} from 'typedoc/dist/lib/models';
import {AggregationSchema, ESNestedAggregation} from './mappings/aggregation-definitions';
import {fieldmap, filterableMap, filterableTagName} from './mappings/definitions/fieldmap';
import {premaps} from './mappings/definitions/premap';
import {settings} from './mappings/definitions/settings';
import {dynamicTypes, ElasticsearchDataType, typemap} from './mappings/definitions/typemap';
import {
  ElasticsearchDynamicTemplate,
  ElasticsearchObject, ElasticsearchTemplateCollection,
  ElasticsearchType,
  ElasticsearchValue,
} from './mappings/mapping-definitions';

let dynamicTemplates: ElasticsearchDynamicTemplate[] = [];
let errors: string[] = [];
let showErrors = true;

let aggregations: AggregationSchema = {};

const indexableTag = 'indexable';
const aggregatableTag = 'aggregatable';
const aggregatableTagParameterGlobal = 'global';

let ignoredTagsList = ['indexable', 'validatable'];

/**
 * Gets all interfaces that have an @indexable tag
 *
 * @param projectReflection the project reflection from which to extract the indexable interfaces
 */
export function getAllIndexableInterfaces(projectReflection: ProjectReflection): DeclarationReflection[] {

  let indexableInterfaces: DeclarationReflection[] = [];

  if (!Array.isArray(projectReflection.children) || projectReflection.children.length === 0) {
    throw new Error('No DeclarationReflections found. Please check your input path');
  }

  // push all declaration reflections into one array
  projectReflection.children.forEach((declarationReflection) => {
    if (Array.isArray(declarationReflection.children)) {
      indexableInterfaces = indexableInterfaces.concat(declarationReflection.children);
    }
  });

  // filter all declaration reflections with an @indexable tag
  indexableInterfaces = indexableInterfaces.filter((declarationReflection) => {
    if (
      typeof declarationReflection.comment === 'undefined' ||
      typeof declarationReflection.comment.tags === 'undefined'
    ) {
      return false;
    }

    return typeof declarationReflection.comment.tags.find((commentTag) => {
      return commentTag.tagName === indexableTag;
    }) !== 'undefined';
  });

  return indexableInterfaces;
}

/**
 * Composes error messages, that are readable and contain a certain minumum of information
 *
 * @param path the path where the error took place
 * @param topTypeName the name of the SCThingType
 * @param typeName the name of the object, with which something went wrong
 * @param object the object or name
 * @param message the error message
 */
function composeErrorMessage(path: string, topTypeName: string, typeName: string, object: string, message: string) {
  const error = `At "${topTypeName}::${path.substr(0, path.length - 1)}" for ${typeName} "${object}": ${message}`;
  errors.push(error);
  if (showErrors) {
    // tslint:disable-next-line:no-floating-promises
    Logger.error(error);
  }
}

/**
 * Gets the Reflections and names for Generics in a ReferenceType of a DeclarationReflection
 *
 * Warning to future maintainers: The code for generics doesn't account for depth. when there is a new generic, it will
 * override the previous one, if there isn't, it will just continue passing it down.
 *
 * @param type the ReferenceType of a DeclarationReflection
 * @param out the previous reflection, it then overrides all parameters or keeps old ones
 * @param path the current path to the object we are in
 * @param tags any tags attached to the type
 */
function getReflectionGeneric(type: ReferenceType,
                              out: Map<string, ElasticsearchValue>,
                              topTypeName: string,
                              path: string, tags: CommentTag[]): Map<string, ElasticsearchValue> {
  if (typeof type.typeArguments !== 'undefined'
    && type.reflection instanceof DeclarationReflection
    && typeof type.reflection.typeParameters !== 'undefined') {
    for (let i = 0; i < type.reflection.typeParameters.length; i++) {
      if (i < type.typeArguments.length) {
        out
          .set(type.reflection.typeParameters[i].name, handleType(type.typeArguments[i], out, topTypeName, path, tags));
      } else {
        // this can happen due to a bug in TypeDoc https://github.com/TypeStrong/typedoc/issues/1061
        // we have no way to know the type here, so we have to use this.
        out.set(type.reflection.typeParameters[i].name, {
          dynamic: true,
          properties: {},
        });

        Logger.warn(`Type "${type.name}": Defaults of generics (Foo<T = any>) currently don't work due to a bug` +
          ` in TypeDoc. It has been replaced by a dynamic type.`);
      }
    }
  }

  return out;
}

/**
 * Handles a ReferenceType that has no value
 *
 * Most of the times that is an external type.
 *
 * @param ref the ReferenceType
 * @param generics the generics from levels above, so we can use them without having access to the parent
 * @param path the current path to the object we are in
 * @param topTypeName the name of the SCThingType
 * @param tags any tags attached to the type
 */
function handleExternalType(ref: ReferenceType, generics: Map<string, ElasticsearchValue>,
                            path: string, topTypeName: string, tags: CommentTag[]): ElasticsearchValue {
  for (const premap in premaps) {
    if (premap === ref.name) {
      return readFieldTags(premaps[premap], path, topTypeName, tags);
    }
  }

  if (ref.name === 'Array') { // basically an external type, but Array is quite common, especially with generics
    if (typeof ref.typeArguments === 'undefined' || typeof ref.typeArguments[0] === 'undefined') {
      composeErrorMessage(path, topTypeName, 'Array with generics', 'array', 'Failed to parse');

      return {type: ElasticsearchDataType.parse_error};
    }

    return readFieldTags(
      handleType(
        ref.typeArguments[0], getReflectionGeneric(
          ref, new Map(generics), path, topTypeName, tags),
        path, topTypeName, tags),
      path, topTypeName, tags);
  }
  if (ref.name === '__type') { // empty object
    return {
      dynamic: 'strict',
      properties: {},
    };
  }

  composeErrorMessage(path, topTypeName, 'external type', ref.name, 'Missing pre-map');

  return readFieldTags({type: ElasticsearchDataType.missing_premap}, path, topTypeName, tags);
}

/**
 * Handles an object
 *
 * @param decl the DeclarationReflection of the object
 * @param generics the generics from levels above, so we can use them without having access to the parent
 * @param path the current path to the object we are in
 * @param topTypeName the name of the SCThingType
 */
function handleDeclarationReflection(decl: DeclarationReflection,
                                     generics: Map<string, ElasticsearchValue>,
                                     path: string,
                                     topTypeName: string,
                                     inheritedTags?: CommentTag[]):
  ElasticsearchValue {
  // check if we have an object referencing a generic
  if (generics.has(decl.name)) { // if the object name is the same as the generic name
    return readFieldTags(generics.get(decl.name) as ElasticsearchObject | ElasticsearchType, path, topTypeName,
      typeof decl.comment !== 'undefined' ? typeof decl.comment.tags !== 'undefined' ? decl.comment.tags : [] : []);
    // use the value defined by the generic

  }

  // start the actual handling process
  const out: ElasticsearchObject = {
    dynamic: 'strict',
    properties: {},
  };

  let empty = true;
  // first check if there are any index signatures, so for example `[name: string]: Foo`
  if (typeof decl.indexSignature !== 'undefined' && typeof decl.indexSignature.parameters !== 'undefined') {
    for (const param of decl.indexSignature.parameters) {
      empty = false;
      const template: ElasticsearchDynamicTemplate = {};
      template[decl.name] = {
        mapping: handleDeclarationReflection(param as DeclarationReflection, new Map(generics), path, topTypeName),
        match: '*',
        match_mapping_type: '*',
        path_match: `${path}*`,
      };
      dynamicTemplates.push(template);
    }
  }

  if (decl.kindString === 'Enumeration') {
    return readTypeTags('string', path, topTypeName, getCommentTags(decl, inheritedTags));
  }

  // check all the children, so in this case we are dealing with an OBJECT
  if (typeof decl.children !== 'undefined' && decl.children.length > 0) {
    for (const child of decl.children) {
      empty = false;
      out.properties[child.name] =
        handleDeclarationReflection(child, new Map(generics), `${path}${child.name}.`, topTypeName);
    }
  } else if (decl.type instanceof Type) { // if the object is a type, so we are dealing with a PROPERTY
    // get inherited tags
    return handleType(decl.type, new Map(generics), path, topTypeName, getCommentTags(decl));
  } else if (decl.kindString === 'Enumeration member') {
    return readTypeTags(typeof decl.defaultValue, path, topTypeName, getCommentTags(decl, inheritedTags));
  }

  if (empty) {
    composeErrorMessage(path, topTypeName, 'object', decl.name, 'Empty object');
  }

  return readFieldTags(out, path, topTypeName, getCommentTags(decl));
}

/**
 * Reads all comment tags, including inherited ones
 *
 * @param decl the DeclarationReflection to read the tags from
 * @param inheritedTags any tags that might have been inherited by a parent
 */
function getCommentTags(decl: DeclarationReflection, inheritedTags: CommentTag[] = []): CommentTag[] {
  let out: CommentTag[] = decl.comment instanceof Comment ?
    typeof decl.comment.tags !== 'undefined' ? decl.comment.tags : inheritedTags : inheritedTags;
  if (decl.overwrites instanceof ReferenceType && decl.overwrites.reflection instanceof DeclarationReflection) {
    out = arrayPriorityJoin(out, getCommentTags(decl.overwrites.reflection));
  }

  return out;
}

/**
 * Joins two arrays of CommentTags, but overrides all original CommentTags with the same tagName
 *
 * @param originals the original array
 * @param overrider the array that should be appended and provide the override values
 */
function arrayPriorityJoin(originals: CommentTag[], overrider: CommentTag[]): CommentTag[] {
  const out: CommentTag[] = overrider;

  originals.forEach((original) => {
    const result = overrider.find((element) => {
      return original.tagName === element.tagName;
    });

    // no support for multiple tags with the same name
    if (!(result instanceof CommentTag)) {
      out.push(original);
    }
  });

  return out;
}

/**
 * Handles UnionTypes
 *
 * Put into a separate function as it is a little bit more complex
 * Works fairly reliable, although there are issues with primitive union types, which don't work at all (And never will)
 *
 * @param type the type object
 * @param generics the generics from levels above, so we can use them without having access to the parent
 * @param path the current path to the object we are in
 * @param topTypeName the name of the SCThingType
 * @param tags any tags attached to the type
 */
function handleUnionType(type: UnionType,
                         generics: Map<string, ElasticsearchValue>,
                         path: string,
                         topTypeName: string,
                         tags: CommentTag[]): ElasticsearchValue {
  const list: ElasticsearchValue[] = [];

  for (const subType of type.types) {
    if (subType instanceof IntrinsicType && subType.name === 'undefined') {
      continue;
    }
    list.push(handleType(subType, new Map(generics), path, topTypeName, tags));
  }

  if (list.length > 0) {
    let out = list[0];

    for (const item of list) {
      out = deepmerge(out, item);
    }

    return out;
  }

  composeErrorMessage(path, topTypeName, 'Union Type', stringify(list),
    'Empty union type. This is likely not a user error.');

  return {type: ElasticsearchDataType.parse_error};
}

/**
 * Serves as a kind of distributor for the different types, should not contain any specific code
 *
 * @param type the type object
 * @param generics the generics from levels above, so we can use them without having access to the parent
 * @param path the current path to the object we are in
 * @param topTypeName the name of the SCThingType
 * @param tags any tags attached to the type
 */
function handleType(type: Type, generics: Map<string, ElasticsearchValue>, path: string, topTypeName: string,
                    tags: CommentTag[]):
  ElasticsearchValue {
  // logger.log((type as any).name);
  if (type instanceof ArrayType) { // array is irrelevant in Elasticsearch, so just go with the element type
    return handleType(type.elementType, new Map(generics), path, topTypeName, tags);
  }
  if (type.type === 'stringLiteral') { // a string literal, usually for type
    return readTypeTags(type.type, path, topTypeName, tags);
  }
  if (type instanceof IntrinsicType) { // the absolute default type, like strings
    return readTypeTags(type.name, path, topTypeName, tags);
  }
  if (type instanceof UnionType) { // the union type...
    return handleUnionType(type, new Map(generics), path, topTypeName, tags);
  }
  if (type instanceof ReferenceType) {
    if (typeof type.reflection !== 'undefined') {
      // there is really no way to make this typesafe, every element in DeclarationReflection is optional.
      return handleDeclarationReflection(type.reflection as DeclarationReflection,
        getReflectionGeneric(type, new Map(generics), path, topTypeName, tags), path, topTypeName, tags);
    }

    return handleExternalType(type, new Map(generics), path, topTypeName, tags);
  }
  if (type instanceof TypeParameterType) {
    // check if we have an object referencing a generic
    if (generics.has(type.name)) {
      return generics.get(type.name) as ElasticsearchObject | ElasticsearchType;
    }
    composeErrorMessage(path, topTypeName, 'Generic', type.name, 'Missing reflection, please report!');

    return {type: ElasticsearchDataType.parse_error};

  }
  if (type instanceof ReflectionType) {
    return readFieldTags(handleDeclarationReflection(type.declaration, new Map(generics), path, topTypeName),
      path, topTypeName, tags);
  }

  composeErrorMessage(path, topTypeName, 'type', stringify(type), 'Not implemented type');

  return {type: ElasticsearchDataType.parse_error};
}

/**
 * Adds an aggregatable to the aggregations list
 *
 * @param path the current path
 * @param topTypeName the name of the top type
 * @param global whether the topTypeName will be used
 */
function addAggregatable(path: string, topTypeName: string, global: boolean) {
  // push type.path and remove the '.' at the end of the path
  const property = path.slice(0, -1)
    .split('.')
    .pop() as string; // cannot be undefined

  (aggregations[global ? '@all' : topTypeName] as ESNestedAggregation).aggs[property] = {
    terms: {
      field: `${property}.raw`,
      size: 1000,
    },
  };
}

/**
 * Reads all tags related to Elasticsearch fields from the fieldMap
 *
 * @param prev the previous ElasticsearchValue, for example and object
 * @param path the current path to the object we are in
 * @param topTypeName the name of the SCThingType
 * @param tags tags attached to the value
 * @param dataType the ElasticsearchDataType, for checking if a tag is a type tag
 */
function readFieldTags(prev: ElasticsearchValue,
                       path: string,
                       topTypeName: string,
                       tags: CommentTag[],
                       dataType?: string): ElasticsearchValue {
  for (const tag of tags) {
    if (tag.tagName === aggregatableTag) {
      addAggregatable(path, topTypeName, tag.text.trim() === aggregatableTagParameterGlobal);
    }

    if (!ignoredTagsList.includes(tag.tagName)) {
      if (typeof fieldmap[tag.tagName] !== 'undefined') {
        if (typeof prev.fields === 'undefined') {
          // create in case it doesn't exist
          prev.fields = {};
        }
        if (tag.text.trim() === '') {
          // merge fields
          prev.fields = {...prev.fields, ...fieldmap[tag.tagName].default};
        } else if (typeof fieldmap[tag.tagName][tag.text.trim()] !== 'undefined') {
          // merge fields
          prev.fields = {...prev.fields, ...fieldmap[tag.tagName][tag.text.trim()]};
        } else if (!fieldmap[tag.tagName].ignore.includes(tag.text.trim())) {
          // when there is an unidentified tag
          composeErrorMessage(path, topTypeName, 'tag', tag.tagName, `Not implemented tag param "${tag.text.trim()}"`);
        }
      } else if (tag.tagName === filterableTagName) {
        if (typeof prev.fields === 'undefined') {
          prev.fields = {};
        }
        if ('type' in prev) {
          const type = filterableMap[prev.type];
          if (typeof type !== 'undefined') {
            // merge fields
            prev.fields = {...prev.fields, ...{raw: {type: type}}};
          } else {
            composeErrorMessage(path, topTypeName, 'tag', tag.tagName, `Not implemented for ${prev.type}`);
          }
        } else {
          composeErrorMessage(path, topTypeName, 'tag', tag.tagName, 'Not applicable for object types');
        }
      } else if (typeof dataType === 'undefined' || typeof typemap[dataType][tag.tagName] === 'undefined') {
        composeErrorMessage(path, topTypeName, 'tag', tag.tagName, `Not implemented tag`);
      }
    }
  }

  return prev;
}

/**
 * Reads all types related to Elasticsearch fields from the fieldMap
 *
 * @param type the type of the value
 * @param path the current path to the object we are in
 * @param topTypeName the name of the SCThingType
 * @param tags tags attached to the value
 */
function readTypeTags(type: string, path: string, topTypeName: string, tags: CommentTag[]): ElasticsearchValue {
  let out: ElasticsearchValue = {type: ElasticsearchDataType.parse_error};

  if (typeof typemap[type] !== 'undefined') { // first look if the value has a definition in the typemap
    for (let i = tags.length - 1; i >= 0; i--) {
      if (!ignoredTagsList.includes(tags[i].tagName) && typeof typemap[type][tags[i].tagName] !== 'undefined') {
        // if we have a tag that indicates a type
        if (out.type !== ElasticsearchDataType.parse_error) {
          composeErrorMessage(path, topTypeName, 'type', type,
            `Type conflict; "${typemap[type][tags[i].tagName]}" would override "${out.type}"`);
          out.type = ElasticsearchDataType.type_conflict;
          continue;
        }
        out.type = typemap[type][tags[i].tagName];
      }
    }

    if (out.type === ElasticsearchDataType.parse_error) {
      out.type = typemap[type].default;
    }

    out = readFieldTags(out, path, topTypeName, tags, type);

    return out;
  }
  if (dynamicTypes.includes(type)) { // Elasticsearch dynamic type TODO: doesn't work for direct types
    return {
      dynamic: true,
      properties: {},
    };
  }

  composeErrorMessage(path, topTypeName, 'type', type, 'Not implemented type');

  return out;
}

/**
 * Takes a project reflection and generates an ElasticsearchTemplate from it
 *
 * Serves as the entry point for getting the mapping, so if you just want to get the mapping files for Elasticsearch,
 * you can do so by calling this function, `RETURNED_VALUE.template` contains the mapping in a fashion that is directly
 * readable by Elasticsearch.
 *
 * @param projectReflection a reflection of the project you want to get the ES Mappings from
 * @param ignoredTags the tag names for which the error output should be suppressed
 * @param showErrorOutput whether to print all errors in the command line or not
 */
export function generateTemplate(projectReflection: ProjectReflection, ignoredTags: string[], showErrorOutput = true):
// tslint:disable-next-line:completed-docs
  { aggregations: AggregationSchema; errors: string[]; mappings: ElasticsearchTemplateCollection; } {
  errors = [];
  aggregations = {
    '@all': {
      aggs: {},
      filter: {
        match_all: {},
      },
    },
  };
  showErrors = showErrorOutput;

  ignoredTagsList = ['indexable', 'validatable'];
  ignoredTagsList.push.apply(ignoredTagsList, ignoredTags);

  const indexableInterfaces = getAllIndexableInterfaces(projectReflection);

  const out: ElasticsearchTemplateCollection = {};

  for (const _interface of indexableInterfaces) {
    if (!Array.isArray(_interface.children) || _interface.children.length === 0) {
      throw new Error('Interface needs at least some properties to be indexable');
    }

    const typeObject = _interface.children.find((declarationReflection) => {
      return declarationReflection.name === 'type';
    });

    if (typeof typeObject === 'undefined' || typeof typeObject.type === 'undefined') {
      throw new Error('Interface needs a type to be indexable');
    }

    let typeName = 'INVALID_TYPE';
    if (typeObject.type instanceof ReferenceType) {
      if (typeObject.type.reflection instanceof DeclarationReflection
        && typeof typeObject.type.reflection.defaultValue === 'string') {
        typeName = typeObject.type.reflection.defaultValue.replace('"', '')
          .replace('"', '');
      } else {
        // tslint:disable-next-line:no-floating-promises
        Logger.error('Your input files seem to be incorrect, or there is a major bug in the mapping generator.');
      }
    } else if (typeObject.type instanceof StringLiteralType) {
      Logger.warn(`The interface ${_interface.name} uses a string literal as type, please use SCThingType.`);
      typeName = typeObject.type.value;
    } else {
      // tslint:disable-next-line:no-floating-promises
      Logger.error(`The interface ${_interface.name} is required to use an SCThingType as a type, please do so.`);
    }

    // init aggregation schema for type
    aggregations[typeName] = {
      aggs: {},
      filter: {
        type: {
          value: typeName,
        },
      },
    };

    let typeNameWithoutSpaces = typeName.toLowerCase();
    while (typeNameWithoutSpaces.includes(' ')) {
      typeNameWithoutSpaces = typeNameWithoutSpaces.replace(' ', '_');
    }
    const templateName = `template_${typeNameWithoutSpaces}`;

    out[templateName] = {
      mappings: {
        [typeName]: handleDeclarationReflection(_interface, new Map(), '', typeName) as ElasticsearchObject,
      },
      settings: settings,
      template: `stapps_${typeNameWithoutSpaces}*`,
    }
    ;
    out[templateName].mappings[typeName].properties.creation_date = {
      type: ElasticsearchDataType.date,
    };

    out[templateName].mappings[typeName].dynamic_templates = dynamicTemplates;

    // Set some properties
    out[templateName].mappings[typeName]._source = {
      excludes: [
        'creation_date',
      ],
    };
    out[templateName].mappings[typeName].date_detection = false;

    dynamicTemplates = [];

    if (Object.keys((aggregations[typeName] as ESNestedAggregation).aggs).length === 0) {
      delete aggregations[typeName];
    }
  }

  return {aggregations, mappings: out, errors};
}