/*
 * FORM METADATA UTILITIES
 *
 * Exports
 * -------
 * autoMeta(model) - generate basic metadata from a raw or mapped model, recursively if necessary
 * combineExtraMeta(metadata, extraMeta) - combine extra metadata into metatdata, lazyly and recursively
 * combineModelWithMeta(model, extraMeta) - automatically generate metadata from model then combine extra metadata
 * execMetaReorderingInstructions(meta) - reorder metadata id ant 'before' or 'after' instructions are found
 * buildFieldSpecificMeta(metadata) - use field-type-specific metadata models to expand metadata
 * extractFieldMappings(metadata) - extrtact mappings from metadata 'source' attributes
 * buildFormGroupFunctionFactory(fb) - return a function to buildFormGroups using the supplied FormBuilder singleton
 * generateNewModel(originalModel, updates) - returns an updated copy of the model
 *
 * Variable names
 * --------------
 * metaF   = metadata for Field
 * metaG   = metadata for Group (possibly nested)
 * metaFoG = metadata for Field or Group
 *
 */

import { FormBuilder, FormGroup, FormArray, FormControl, ValidatorFn, AsyncValidatorFn } from '@angular/forms';
import { reduce, cloneDeep } from 'lodash/fp';
import * as fmdModels from '../models/field.model';

// REMINDER: Import this directly from @angular/forms when we upgrade to Angular 6
// While we're still on Angular 5 just declare it
interface AbstractControlOptions {
	validators?: ValidatorFn | ValidatorFn[] | null;
	asyncValidators?: AsyncValidatorFn | AsyncValidatorFn[] | null;
	updateOn?: 'change' | 'blur' | 'submit';
}


// ---------------------------------------------------------------------------------------------------------------------
// AutoMeta: Generate Automatic Metadata from a raw model (or mapped raw model)
// ---------------------------------------------------------------------------------------------------------------------

const isScalar = val => typeof val === 'boolean' || typeof val === 'number' || typeof val === 'string';
const isArray = val => Array.isArray(val);

const keyValPairToMeta = (val, key) => ({ name: key, [isScalar(val) ? 'value' : 'meta']: val });
const keyValPairToMetaRecursive = ( [key, val] ) => {
	if (val === null || val === undefined) {
		val = ''; // Treat null or undefined as empty string, for purpose of form
	}
	const innerVal = isScalar(val) ? val : (isArray(val) ? arrayToMeta(val) : autoMeta(val));
	const metaVal = keyValPairToMeta(innerVal, key);
	return [key, metaVal];
};
const arrayMemberAutoName = val => isScalar(val) ? val : val.__typename || val.constructor.name;
const arrayToMeta = array => array.map(val => ({ name: arrayMemberAutoName(val), 'value' : val }));

const autoMeta = model => Object.entries(model)
	.filter(kvPair => kvPair[0] !== '__')
	.map(keyValPairToMetaRecursive)
	.reduce((res, [key, val]) => addProp(res, key, val), {});


// ---------------------------------------------------------------------------------------------------------------------
// Combine automatically generated metadata with overrides
// ---------------------------------------------------------------------------------------------------------------------

// containerSeed = Metadata from container which seeds all contained fields

const combineMetaForField = (metaF, containerSeed, extraMetaF) => Object.assign(metaF, containerSeed, extraMetaF);
const combineExtraMeta = (metaG, extraMeta, createFromExtra = false, containerSeed = {}) => {
	const combinedMeta = {};
	Object.entries(extraMeta).forEach(([key, val]) => {
		if (typeof metaG[key] === 'object' || createFromExtra) {
			const isCon = isContainer(val);
			const metaFoG = metaG[key] || {};
			const seed = isCon ? {} : containerSeed; // Container's don't seed themselves
			const extra = isCon ?
				{
					...val,
					meta: combineExtraMeta( // RECURSION
						metaFoG.meta || {},
						val['meta'],
						createFromExtra,
						val['seed'] || containerSeed // Inherit seeded data if this group's seed isn't set
					)
				}
				:
				val;
			combinedMeta[key] = combineMetaForField(metaFoG, seed, extra);
		}
	});
	return { ...metaG, ...combinedMeta };
};

// Combine model with overrides (after automatically generating metadata from the model)
const combineModelWithMeta = (model, extraMeta, createFromExtra = false) => combineExtraMeta(autoMeta(model), extraMeta, createFromExtra);


// ---------------------------------------------------------------------------------------------------------------------
// Build Form-Field-Type-Specific Metadata (using the field models in dynaform/models)
// ---------------------------------------------------------------------------------------------------------------------

const buildFieldClassName = (t = 'text') => {
	const start = t[0].toUpperCase() + t.slice(1);
	if (start === 'Container' || start === 'Heading' || t.slice(-5) === 'Group') {
		return start;
	}
	return start + 'Field';
};

const buildModeledField = metaFoG => {
	const type = isContainer(metaFoG) ? 'container' : metaFoG.type;
	const className = buildFieldClassName(type);
	if (!fmdModels[className]) {
		throw new Error(`No metadata model "${className}" for type "${type}"`);
	}
	return new fmdModels[className](metaFoG);
};

// Build Form Group Member
const buildModeledFieldGroupMember = metaFoG => {
	const modeledGroupMember = buildModeledField(metaFoG);
	if (isContainer(metaFoG)) {
		modeledGroupMember.meta = _buildFieldSpecificMeta(metaFoG.meta);
	}
	return modeledGroupMember;
};

// Build Form Group
const buildModeledFieldGroupReducerIteree = (res, metaFoG) => Object.assign(res, { [metaFoG.name]: buildModeledFieldGroupMember(metaFoG) });
const _buildFieldSpecificMeta = metaG => reduce(buildModeledFieldGroupReducerIteree, {}, metaG);
const buildFieldSpecificMeta = metaG => _buildFieldSpecificMeta(addMissingNames(metaG));


// ---------------------------------------------------------------------------------------------------------------------
// Generate mapping from source attributes
// (used to grab data from model when using METAFIRST form generation)
// ---------------------------------------------------------------------------------------------------------------------

// Each container CAN have a datasource instead of the original model
// SO ... If container source is a functional mapping, store the mapping to get datasource object later

const isAbsPath = path => typeof path === 'string' && path[0] === '/';
const isRootPath = path => path === '/';
const processPath = (parentPath, path) => isAbsPath(path) ? path : `${parentPath}.${path}`;

const prependParentPathRecursive = (parentPath: string, obj: StringMap) => {
	return Object.entries(obj)
		.map( ([key, mapping] ) => {
			let mappingRes;
			switch (typeof mapping) {
				case 'string':
					mappingRes = processPath(parentPath, mapping);
					break;
				case 'object':
					if (Array.isArray(mapping)) {
						// A functional mapping of the form [fn, fn] or [source, fn, fn]
						if (typeof mapping[0] === 'string') {
							const source = processPath(parentPath, mapping[0]);
							mappingRes = [source, ...mapping.slice(1)];
						} else {
							const source = processPath(parentPath, mapping);
							mappingRes = [source, ...mapping];
						}
					} else {
						mappingRes = prependParentPathRecursive(parentPath, mapping);
					}
					break;
			}
			return [key, mappingRes];
		})
		.reduce((acc, [key, val]) => addProp(acc, key, val), {});
};

const _extractFieldMapping = ( [key, metaFoG] ) => {
	let source;
	if (isGroup(metaFoG)) {
		if (Array.isArray(metaFoG.source)) {
			source = extractFieldMappings(metaFoG.meta);
			source.__ = metaFoG.source; // Store the functional mapping (including function executed later to provide container's data)
		} else {
			source = extractFieldMappings(metaFoG.meta, metaFoG.source || key);
		}
	} else {
		source = metaFoG.source || key;
	}
	return [key, source];
};

const extractFieldMappings = (metaG, parentPath = '') => Object.entries(metaG)
	.map(_extractFieldMapping)
	.reduce((res, [key, mapping]) => {

		// Work out the path prefix
		let prefix;
		if (parentPath) {
			if (isRootPath(parentPath) || isAbsPath(metaG[key].source) || Array.isArray(parentPath)) {
				// If the parentPath is the root of the data structure, or the source is an absolute path or functional datasource,
				// then there's no path prefix
				prefix = '';
			} else {
				// Otherwise create a prefix from the parentPath
				prefix = parentPath ? (parentPath[0] === '/' ? parentPath.slice(1) : parentPath) : '';
			}
		}

		// Work out the mapping result
		let	mappingRes;
		if (typeof mapping === 'string') {

			// DIRECT MAPPING
			if (mapping[0] === '/') {
				mappingRes = mapping.slice(1);
			} else if (prefix) {
				mappingRes = `${prefix}.${mapping}`;
			} else {
				mappingRes = mapping;
			}

		} else if (Array.isArray(mapping)) {

			// FUNCTIONAL MAPPING
			// of the form [fn, fn] or [source, fn, fn]
			if (prefix) {
				if (typeof mapping[0] === 'function') {
					// Mapping of form [fn, fn] with existing parent path
					mappingRes = [`${prefix}.${key}`, ...mapping];
				} else if (typeof mapping[0] === 'string') {
					// Mapping of form [source, fn, fn] with existing parent path
					const source = mapping[0][0] === '/' ? mapping[0].slice(1) : `${prefix}.${mapping[0]}`;
					mappingRes = [source, ...mapping.slice(1)];
				}
			} else {
				if (typeof mapping[0] === 'function') {
					// Mapping of form [fn, fn] with NO parent path
					mappingRes = [key, ...mapping];
				} else if (typeof mapping[0] === 'string') {
					// Mapping of form [source, fn, fn] with NO parent path
					const source = mapping[0][0] === '/' ? mapping[0].slice(1) : mapping[0];
					mappingRes = [source, ...mapping.slice(1)];
				}
			}

		} else if (typeof mapping === 'object' && prefix && !mapping.__) {

			// CONTAINER with parentPath, and WITHOUT its own functional datasource stored in __
			// For every contained value recursively prepend the parentPath to give an absolute path
			mappingRes = prependParentPathRecursive(prefix, mapping);

		} else {

			mappingRes = mapping;

		}

		return addProp(res, key, mappingRes);
	}, {});


// ---------------------------------------------------------------------------------------------------------------------
// Build Form Group Function Factory
// returns a function to build FormGroups containing FormControls, FormArrays and other FormGroups
// ---------------------------------------------------------------------------------------------------------------------

const buildFormGroupFunctionFactory = (fb: FormBuilder): (meta) => FormGroup => {
	// Establishes a closure over the supplied FormBuilder and returns a function that builds FormGroups from metadata
	// ( it's done this way so we can use the FormBuilder singleton without reinitialising )

	// Build Form Control
	const buildControlState = metaF => ({ value: metaF.value || metaF.default, disabled: metaF.isDisabled });
	const buildValidators = (metaF): AbstractControlOptions => ({
		validators: metaF.validators,
		asyncValidators: metaF.asyncValidators,
		// blur not working for custom components, so use change for custom and blur for text
		updateOn: metaF.type === 'text' || metaF.type === 'textarea' ? 'blur' : 'change'
	});
	const buildFormControl = metaF => new FormControl(buildControlState(metaF), buildValidators(metaF));

	// Build Form Array
	const buildFormArray = (metaG): FormArray => fb.array(metaG.map(metaF => buildFormControl(metaF)));

	// Build Form Group Member - builds a FormControl, FormArray, or another FormGroup which can contain any of these
	const buildFormGroupMember = metaFoG => isGroup(metaFoG) ?
		(isArray(metaFoG.meta) ? buildFormArray(metaFoG.meta) : _buildFormGroup(metaFoG.meta)) :
		buildFormControl(metaFoG);

	const buildFormGroupReducerIteree = (res, metaFoG) => {
		return metaFoG.noFormControls ? res : Object.assign(res, { [metaFoG.name]: buildFormGroupMember(metaFoG) });
	};
	const _buildFormGroup = _metaG => fb.group(reduce(buildFormGroupReducerIteree, {}, _metaG));

	// The main function - builds FormGroups containing other FormGroups, FormArrays and FormControls
	const buildFormGroup = metaG => {
		// Ensure that we have Field-Specific Metadata, not raw Objects
		const metaWithNameKeys = addMissingNames(metaG);
		// MAYBE only run this if first entry isn't right, for reasons of efficiency
		const fieldModeledMeta = addMissingFieldSpecificMeta(metaWithNameKeys);
		return _buildFormGroup(fieldModeledMeta);
	};
	return buildFormGroup;
};


// ---------------------------------------------------------------------------------------------------------------------
// Reordering ( support for before / after instructions in metadata )
// ---------------------------------------------------------------------------------------------------------------------

// Object slice function
const slice = (obj, start, end = null) => Object.entries(obj)
	.slice(start, end !== null ? end : Object.keys(obj).length)
	.reduce((res, [key, val]) => addProp(res, key, val), {});

const objConcat = (obj, pos, key, val = null) => {
	const existsAlready = Object.keys(obj).indexOf(key);
	if (existsAlready) {
		val = obj[key];
	}
	const start  = slice(obj, 0, pos);
	const finish = slice(obj, pos);
	delete start[key];
	delete finish[key];
	return { ...start, [key]: val, ...finish };
};

const insertBefore = (obj, beforeKey, key, val = null) => {
	const targetPosition = Object.keys(obj).indexOf(beforeKey);
	return objConcat(obj, targetPosition, key, val);
};

const insertAfter = (obj, afterKey, key, val = null) => {
	const targetPosition = Object.keys(obj).indexOf(afterKey) + 1;
	return objConcat(obj, targetPosition, key, val);
};

// Process reordeing instructions recursively
const _execMetaReorderingInstructions = (metaG: StringMap) => {
	let reorderedGroup = { ...metaG };
	Object.entries(metaG).forEach(([key, metaFoG]) => {
		if (metaFoG.before) {
			reorderedGroup = insertBefore(reorderedGroup, metaFoG.before, key);
		} else if (metaFoG.after) {
			reorderedGroup = insertAfter(reorderedGroup, metaFoG.after, key);
		}
		if (isContainer(metaFoG)) {
			reorderedGroup[key].meta = execMetaReorderingInstructions(metaFoG.meta);
		}
	});
	return reorderedGroup;
};

const execMetaReorderingInstructions = (metaG: StringMap) => {
	return _execMetaReorderingInstructions(cloneDeep(metaG));
};


// ---------------------------------------------------------------------------------------------------------------------
// Generate new model, without mutating original
// (used to produce an updated copy of a model when form values are changed - will not create new keys)
// ---------------------------------------------------------------------------------------------------------------------

const generateNewModel = (originalModel, updates) => {
	return updateObject(originalModel, updates);
};

const updateObject = (obj, updates, createAdditionalKeys = false) => {
	// THIS DOES NOT MUTATE obj, instead returning a new object
	const shallowClone = { ...obj };
	Object.entries(updates).forEach(([key, val]) => safeSet(shallowClone, key, val, createAdditionalKeys));
	return shallowClone;
};

const safeSet = (obj, key, val, createAdditionalKeys = false) => {
	// THIS MUTATES obj - consider the wisdom of this
	if (!createAdditionalKeys && !obj.hasOwnProperty(key)) {
		return;
	}
	const currentVal = obj[key];
	if (val === currentVal) {
		return;
	}
	if (nullOrScaler(currentVal)) {
		console.log('safeSet nullOrScaler', key, val);
		obj[key] = val;
	} else {
		if (Array.isArray(currentVal)) {
			if (typeof val === 'object') {
				// Replace array
				console.log('safeSet array', key, val);
				obj[key] = Array.isArray(val) ? val : Object.values(val);
			} else {
				// Append to end of existing array? Create a single element array?
				throw new Error(`safeSet Error: Expected array or object @key ${key} but got scalar
				Rejected update was ${val}`);
			}
		} else if (typeof val === 'object') {
			// Deep merge
			obj[key] = updateObject(obj[key], val, createAdditionalKeys);
		} else {
			throw new Error(`safeSet Error: Can't deep merge object into scalar @key ${key}
							Rejected update was ${val}`);
		}
	}
};

const nullOrScaler = val => {
	if (val === null) { return true; }
	const t = typeof val;
	return t === 'number' || t === 'string' || t === 'boolean';
};


// ---------------------------------------------------------------------------------------------------------------------
// Helper Functions
// ---------------------------------------------------------------------------------------------------------------------

// Add Property to object, returning updated object
const addProp = (obj, key, val) => { obj[key] = val; return obj; };

// Is Group
// Helper function to distinguish group from field
const isGroup = (metaFoG): boolean => !!metaFoG.meta;

// Is Container
// Helper function to distinguish container group (a group of child fields)
const isContainer = (metaFoG): boolean => isGroup(metaFoG) && (!metaFoG.type || metaFoG.type.toLowerCase() === 'container');

// Add Missing Names
// Helper function to add any missing 'name' properties to Fields and Groups using property's key, recursively
const addNameIfMissing = (metaFoG, key) => metaFoG.name ? metaFoG : addProp(metaFoG, 'name', key);
const addNameToSelfAndChildren = ( [key, metaFoG] ) => {
	metaFoG = addNameIfMissing(metaFoG, key);
	if (isGroup(metaFoG)) {
		metaFoG.meta = isArray(metaFoG.meta) ? Object.values(addMissingNames(metaFoG.meta)) : addMissingNames(metaFoG.meta); // Recursion
	}
	return [key, metaFoG];
};
const addMissingNames = metaG => Object.entries(metaG)
	.map(addNameToSelfAndChildren)
	.reduce((res, [key, val]) => addProp(res, key, val), {});


// Add Missing Field-Specific Meta
// Helper function to add any missing Field-Specific Metadata  (using models in dynaform/models), recursively
// Checks the constrctor, which should NOT be a plain Object, but rather TextField, TextareaField, SelectField, etc.
const add_FSM_IfMissing = metaFoG => metaFoG.constructor.name === 'Object' ? buildModeledFieldGroupMember(metaFoG) : metaFoG;
const add_FSM_ToSelfAndChildren = ( [key, metaFoG] ) => {
	metaFoG = add_FSM_IfMissing(metaFoG);
	return [key, metaFoG];
};
const addMissingFieldSpecificMeta = metaG => Object.entries(metaG)
	.map(add_FSM_ToSelfAndChildren)
	.reduce((res, [key, val]) => addProp(res, key, val), {});


// ---------------------------------------------------------------------------------------------------------------------
// Exports
// ---------------------------------------------------------------------------------------------------------------------

export {
	autoMeta, combineModelWithMeta, combineExtraMeta, execMetaReorderingInstructions,
	buildFieldSpecificMeta, extractFieldMappings, buildFormGroupFunctionFactory,
	generateNewModel
};