// *****************************************************************************
// Copyright (C) 2018 Ericsson and others.
//
// This program and the accompanying materials are made available under the
// terms of the Eclipse Public License v. 2.0 which is available at
// http://www.eclipse.org/legal/epl-2.0.
//
// This Source Code may also be made available under the following Secondary
// Licenses when the conditions for such availability set forth in the Eclipse
// Public License v. 2.0 are satisfied: GNU General Public License, version 2
// with the GNU Classpath Exception which is available at
// https://www.gnu.org/software/classpath/license.html.
//
// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-only WITH Classpath-exception-2.0
// *****************************************************************************

/* eslint-disable @typescript-eslint/no-explicit-any */

import { JSONValue } from '@lumino/coreutils';
import { inject, injectable, postConstruct } from 'inversify';
import { Disposable, DisposableCollection } from '../disposable';
import { Emitter, Event } from '../event';
import { Deferred } from '../promise-util';
import URI from '../uri';
import { OverridePreferenceName, PreferenceLanguageOverrideService } from './preference-language-override-service';
import { PreferenceProvider, PreferenceProviderDataChange, PreferenceProviderDataChanges, PreferenceResolveResult, PreferenceUtils } from './preference-provider';
import { PreferenceSchemaService } from './preference-schema';
import { PreferenceScope } from './preference-scope';
import { PreferenceConfigurations } from './preference-configurations';
import { deepFreeze } from '../objects';
import { unreachable } from '../types';

/**
 * Representation of a preference change. A preference value can be set to `undefined` for a specific scope.
 * This means that the value from a more general scope will be used.
 */
export interface PreferenceChange extends Omit<PreferenceProviderDataChange, 'newValue' | 'oldValue'> {
    /**
     * Tests wether the given resource is affected by the preference change.
     * @param resourceUri the uri of the resource to test.
     */
    affects(resourceUri?: string): boolean;
}

export class PreferenceChangeImpl implements PreferenceChange {
    protected readonly change: PreferenceProviderDataChange;
    constructor(change: PreferenceProviderDataChange) {
        this.change = deepFreeze(change);
    }

    get preferenceName(): string {
        return this.change.preferenceName;
    }
    get scope(): PreferenceScope {
        return this.change.scope;
    }
    get domain(): string[] | undefined {
        return this.change.domain;
    }

    // TODO add tests
    affects(resourceUri?: string): boolean {
        const resourcePath = resourceUri && new URI(resourceUri).path;
        const domain = this.change.domain;
        return !resourcePath || !domain || domain.some(uri => new URI(uri).path.relativity(resourcePath) >= 0);
    }
}
/**
 * A key-value storage for {@link PreferenceChange}s. Used to aggregate multiple simultaneous preference changes.
 */
export interface PreferenceChanges {
    [preferenceName: string]: PreferenceChange
}

export const PreferenceService = Symbol('PreferenceService');
/**
 * Service to manage preferences including, among others, getting and setting preference values as well
 * as listening to preference changes.
 *
 * Depending on your use case you might also want to look at {@link createPreferenceProxy} with which
 * you can easily create a typesafe schema-based interface for your preferences. Internally the proxy
 * uses the PreferenceService so both approaches are compatible.
 */
export interface PreferenceService extends Disposable {
    /**
     * Promise indicating whether the service successfully initialized.
     */
    readonly ready: Promise<void>;
    /**
     * Indicates whether the service has successfully initialized. Will be `true` when {@link PreferenceService.ready the `ready` Promise} resolves.
     */
    readonly isReady: boolean;
    /**
     * Retrieve the stored value for the given preference.
     *
     * @param preferenceName the preference identifier.
     *
     * @returns the value stored for the given preference when it exists, `undefined` otherwise.
     */
    get<T>(preferenceName: string): T | undefined;
    /**
     * Retrieve the stored value for the given preference.
     *
     * @param preferenceName the preference identifier.
     * @param defaultValue the value to return when no value for the given preference is stored.
     *
     * @returns the value stored for the given preference when it exists, otherwise the given default value.
     */
    get<T>(preferenceName: string, defaultValue: T): T;
    /**
     * Retrieve the stored value for the given preference and resourceUri.
     *
     * @param preferenceName the preference identifier.
     * @param defaultValue the value to return when no value for the given preference is stored.
     * @param resourceUri the uri of the resource for which the preference is stored. This used to retrieve
     * a potentially different value for the same preference for different resources, for example `files.encoding`.
     *
     * @returns the value stored for the given preference and resourceUri when it exists, otherwise the given
     * default value.
     */
    get<T>(preferenceName: string, defaultValue: T, resourceUri?: string): T;
    /**
     * Retrieve the stored value for the given preference and resourceUri.
     *
     * @param preferenceName the preference identifier.
     * @param defaultValue the value to return when no value for the given preference is stored.
     * @param resourceUri the uri of the resource for which the preference is stored. This used to retrieve
     * a potentially different value for the same preference for different resources, for example `files.encoding`.
     *
     * @returns the value stored for the given preference and resourceUri when it exists, otherwise the given
     * default value.
     */
    get<T>(preferenceName: string, defaultValue?: T, resourceUri?: string): T | undefined;
    /**
     * Sets the given preference to the given value.
     *
     * @param preferenceName the preference identifier.
     * @param value the new value of the preference.
     * @param scope the scope for which the value shall be set, i.e. user, workspace etc.
     * When the folder scope is specified a resourceUri must be provided.
     * @param resourceUri the uri of the resource for which the preference is stored. This used to store
     * a potentially different value for the same preference for different resources, for example `files.encoding`.
     *
     * @returns a promise which resolves to `undefined` when setting the preference was successful. Otherwise it rejects
     * with an error.
     */
    set(preferenceName: string, value: any, scope?: PreferenceScope, resourceUri?: string): Promise<void>;

    /**
     * Determines and applies the changes necessary to apply `value` to either the `resourceUri` supplied or the active session.
     * If there is no setting for the `preferenceName`, the change will be applied in user scope.
     * If there is a setting conflicting with the specified `value`, the change will be applied in the most specific scope with a conflicting value.
     *
     * @param preferenceName the identifier of the preference to modify.
     * @param value the value to which to set the preference. `undefined` will reset the preference to its default value.
     * @param resourceUri the uri of the resource to which the change is to apply. If none is provided, folder scope will be ignored.
     */
    updateValue(preferenceName: string, value: any, resourceUri?: string): Promise<void>

    /**
     * Registers a callback which will be called whenever a preference is changed.
     */
    onPreferenceChanged: Event<PreferenceChange>;
    /**
     * Registers a callback which will be called whenever one or more preferences are changed.
     */
    onPreferencesChanged: Event<PreferenceChanges>;
    /**
     * Retrieve the stored value for the given preference and resourceUri in all available scopes.
     *
     * @param preferenceName the preference identifier.
     * @param resourceUri the uri of the resource for which the preference is stored.
     * @param forceLanguageOverride if `true` and `preferenceName` is a language override, only values for the specified override will be returned.
     * Otherwise, values for the override will be returned where defined, and values from the base preference will be returned otherwise.
     *
     * @return an object containing the value of the given preference for all scopes.
     */
    inspect<T extends JSONValue>(preferenceName: string, resourceUri?: string, forceLanguageOverride?: boolean): PreferenceInspection<T> | undefined;
    /**
     * For behavior, see {@link PreferenceService.inspect}.
     *
     * @returns the value in the scope specified.
     */
    inspectInScope<T extends JSONValue>(preferenceName: string, scope: PreferenceScope, resourceUri?: string, forceLanguageOverride?: boolean): T | undefined
    /**
     * Returns a new preference identifier based on the given OverridePreferenceName.
     *
     * @param options the override specification.
     *
     * @returns the calculated string based on the given OverridePreferenceName.
     */
    overridePreferenceName(options: OverridePreferenceName): string;
    /**
     * Tries to split the given preference identifier into the original OverridePreferenceName attributes
     * with which this identifier was created. Returns `undefined` if this is not possible, for example
     * when the given preference identifier was not generated by `overridePreferenceName`.
     *
     * This method is checked when resolving preferences. Therefore together with "overridePreferenceName"
     * this can be used to handle specialized preferences, e.g. "[markdown].editor.autoIndent" and "editor.autoIndent".
     *
     * @param preferenceName the preferenceName which might have been created via {@link PreferenceService.overridePreferenceName}.
     *
     * @returns the OverridePreferenceName which was used to create the given `preferenceName` if this was the case,
     * `undefined` otherwise.
     */
    overriddenPreferenceName(preferenceName: string): OverridePreferenceName | undefined;
    /**
     * Retrieve the stored value for the given preference and resourceUri.
     *
     * @param preferenceName the preference identifier.
     * @param defaultValue the value to return when no value for the given preference is stored.
     * @param resourceUri the uri of the resource for which the preference is stored. This used to retrieve
     * a potentially different value for the same preference for different resources, for example `files.encoding`.
     *
     * @returns an object containing the value stored for the given preference and resourceUri when it exists,
     * otherwise the given default value. If determinable the object will also contain the uri of the configuration
     * resource in which the preference was stored.
     */
    resolve<T>(preferenceName: string, defaultValue?: T, resourceUri?: string): PreferenceResolveResult<T>;
    /**
     * Returns the uri of the configuration resource for the given scope and optional resource uri.
     *
     * @param scope the PreferenceScope to query for.
     * @param resourceUri the optional uri of the resource-specific preference handling
     * @param sectionName the optional preference section to query for.
     *
     * @returns the uri of the configuration resource for the given scope and optional resource uri it it exists,
     * `undefined` otherwise.
     */
    getConfigUri(scope: PreferenceScope, resourceUri?: string, sectionName?: string): URI | undefined;
}

/**
 * Return type of the {@link PreferenceService.inspect} call.
 */
export interface PreferenceInspection<T = JSONValue> {
    /**
     * The preference identifier.
     */
    preferenceName: string,
    /**
     * Value in default scope.
     */
    defaultValue: T | undefined,
    /**
     * Value in user scope.
     */
    globalValue: T | undefined,
    /**
     * Value in workspace scope.
     */
    workspaceValue: T | undefined,
    /**
     * Value in folder scope.
     */
    workspaceFolderValue: T | undefined,
    /**
     * The value that is active, i.e. the value set in the lowest scope available.
     */
    value: T | undefined;
}

export type PreferenceInspectionScope = keyof Omit<PreferenceInspection<unknown>, 'preferenceName'>;

/**
 * We cannot load providers directly in the case if they depend on `PreferenceService` somehow.
 * It allows to load them lazily after DI is configured.
 */
export const PreferenceProviderProvider = Symbol('PreferenceProviderProvider');
export type PreferenceProviderProvider = (scope: PreferenceScope, uri?: URI) => PreferenceProvider | undefined;

@injectable()
export class PreferenceServiceImpl implements PreferenceService {

    protected readonly onPreferenceChangedEmitter = new Emitter<PreferenceChange>();
    readonly onPreferenceChanged = this.onPreferenceChangedEmitter.event;

    protected readonly onPreferencesChangedEmitter = new Emitter<PreferenceChanges>();
    readonly onPreferencesChanged = this.onPreferencesChangedEmitter.event;

    protected readonly toDispose = new DisposableCollection(this.onPreferenceChangedEmitter, this.onPreferencesChangedEmitter);

    @inject(PreferenceSchemaService)
    protected readonly schemaService: PreferenceSchemaService;

    @inject(PreferenceProviderProvider)
    protected readonly providerProvider: PreferenceProviderProvider;

    @inject(PreferenceConfigurations)
    protected readonly configurations: PreferenceConfigurations;

    @inject(PreferenceLanguageOverrideService)
    protected readonly preferenceOverrideService: PreferenceLanguageOverrideService;

    protected readonly preferenceProviders = new Map<PreferenceScope, PreferenceProvider>();

    protected async initializeProviders(): Promise<void> {
        try {
            for (const scope of this.schemaService.validScopes) {
                const provider = this.providerProvider(scope);
                if (provider) {
                    this.preferenceProviders.set(scope, provider);
                    this.toDispose.push(provider.onDidPreferencesChanged(changes =>
                        this.reconcilePreferences(changes)
                    ));
                    await provider.ready;
                } else {
                    console.warn(`No preference provider bound for ${PreferenceScope[scope]}`);
                }
            }
            this._ready.resolve();
            this._isReady = true;
        } catch (e) {
            this._ready.reject(e);
        }
    }

    @postConstruct()
    protected init(): void {
        this.toDispose.push(Disposable.create(() => this._ready.reject(new Error('preference service is disposed'))));
        this.initializeProviders();
    }

    dispose(): void {
        this.toDispose.dispose();
    }

    protected readonly _ready = new Deferred<void>();
    get ready(): Promise<void> {
        return this._ready.promise;
    }

    protected _isReady = false;
    get isReady(): boolean {
        return this._isReady;
    }

    protected reconcilePreferences(changes: PreferenceProviderDataChanges): void {
        const changesToEmit: PreferenceChanges = {};
        const acceptChange = (change: PreferenceProviderDataChange) => {
            this.getAffectedPreferenceNames(change, preferenceName =>
                changesToEmit[preferenceName] = new PreferenceChangeImpl({ ...change, preferenceName }));
        };

        for (const preferenceName of Object.keys(changes)) {

            let change = changes[preferenceName];
            const overridden = this.overriddenPreferenceName(change.preferenceName);
            if (change.newValue === undefined) {
                if (overridden) {
                    change = {
                        ...change, newValue: this.doGet(overridden.preferenceName)
                    };
                }
            }

            for (const scope of [...this.schemaService.validScopes].reverse()) {
                const provider = this.getProvider(scope);
                if (provider) {
                    const scopeValue: JSONValue | undefined = provider.get(preferenceName);
                    if (scope > change.scope && scopeValue !== undefined) {
                        const preference = this.schemaService.getSchemaProperty(change.preferenceName);
                        if (!preference?.type || preference.type === 'object' || preference.type === 'array'
                            || Array.isArray(preference.type) && preference.type.some(candidate => candidate === 'object' || candidate === 'array')) {
                            // Merge object/array preferences
                            acceptChange(change);
                        }
                        break;
                    }
                    // Handle changes in the same scope
                    if (scope === change.scope) {
                        const hasNewValue = change.newValue !== undefined || scope === PreferenceScope.Default;
                        const isResetToUndefined = change.newValue === undefined && scopeValue === undefined; // is reset to undefined (no default value)
                        if (hasNewValue || isResetToUndefined) {
                            acceptChange(change);
                            break;
                        }
                    }
                    // Handle fallback to more general scope when preference is reset
                    if (scope < change.scope && change.newValue === undefined && scopeValue !== undefined) {
                        // preference is changed to `undefined`, use the value from a more general scope
                        change = {
                            ...change,
                            newValue: scopeValue,
                            scope
                        };
                        acceptChange(change);
                        break;
                    }
                }
            }
        }

        // emit the changes
        const changedPreferenceNames = Object.keys(changesToEmit);
        if (changedPreferenceNames.length > 0) {
            this.onPreferencesChangedEmitter.fire(changesToEmit);
        }
        changedPreferenceNames.forEach(preferenceName => this.onPreferenceChangedEmitter.fire(changesToEmit[preferenceName]));
    }
    protected getAffectedPreferenceNames(change: PreferenceProviderDataChange, accept: (affectedPreferenceName: string) => void): void {
        const overridden = this.preferenceOverrideService.overriddenPreferenceName(change.preferenceName);
        accept(change.preferenceName);
        if (!overridden?.overrideIdentifier) { // changes to overrides never affect other overrides
            const preference = this.schemaService.getSchemaProperty(change.preferenceName);
            if (preference && preference.overridable) {

                for (const overrideId of this.schemaService.overrideIdentifiers) {
                    const overridePreferenceName = this.preferenceOverrideService.overridePreferenceName({
                        overrideIdentifier: overrideId,
                        preferenceName: change.preferenceName
                    });

                    if (!this.doHas(overridePreferenceName)) {
                        accept(overridePreferenceName);
                    }
                }
            }
        }
    }

    protected getProvider(scope: PreferenceScope): PreferenceProvider | undefined {
        return this.preferenceProviders.get(scope);
    }

    has(preferenceName: string, resourceUri?: string): boolean {
        return this.get(preferenceName, undefined, resourceUri) !== undefined;
    }

    get<T>(preferenceName: string): T | undefined;
    get<T>(preferenceName: string, defaultValue: T): T;
    get<T>(preferenceName: string, defaultValue: T, resourceUri: string): T;
    get<T>(preferenceName: string, defaultValue?: T, resourceUri?: string): T | undefined;
    get<T>(preferenceName: string, defaultValue?: T, resourceUri?: string): T | undefined {
        return this.resolve<T>(preferenceName, defaultValue, resourceUri).value;
    }

    resolve<T>(preferenceName: string, defaultValue?: T, resourceUri?: string): PreferenceResolveResult<T> {
        const { value, configUri } = this.doResolve(preferenceName, defaultValue, resourceUri);
        if (value === undefined) {
            const overridden = this.overriddenPreferenceName(preferenceName);
            if (overridden) {
                return this.doResolve(overridden.preferenceName, defaultValue, resourceUri);
            }
        }
        return { value, configUri };
    }

    async set(preferenceName: string, value: any, scope: PreferenceScope | undefined, resourceUri?: string): Promise<void> {
        const resolvedScope = scope ?? (!resourceUri ? PreferenceScope.Workspace : PreferenceScope.Folder);
        if (resolvedScope === PreferenceScope.Folder && !resourceUri) {
            throw new Error('Unable to write to Folder Settings because no resource is provided.');
        }
        const provider = this.getProvider(resolvedScope);
        if (provider && await provider.setPreference(preferenceName, value, resourceUri)) {
            return;
        }
        throw new Error(`Unable to write to ${PreferenceScope[resolvedScope]} Settings.`);
    }

    getBoolean(preferenceName: string): boolean | undefined;
    getBoolean(preferenceName: string, defaultValue: boolean): boolean;
    getBoolean(preferenceName: string, defaultValue: boolean, resourceUri: string): boolean;
    getBoolean(preferenceName: string, defaultValue?: boolean, resourceUri?: string): boolean | undefined {
        const value = resourceUri ? this.get(preferenceName, defaultValue, resourceUri) : this.get(preferenceName, defaultValue);
        // eslint-disable-next-line no-null/no-null
        return value !== null && value !== undefined ? !!value : defaultValue;
    }

    getString(preferenceName: string): string | undefined;
    getString(preferenceName: string, defaultValue: string): string;
    getString(preferenceName: string, defaultValue: string, resourceUri: string): string;
    getString(preferenceName: string, defaultValue?: string, resourceUri?: string): string | undefined {
        const value = resourceUri ? this.get(preferenceName, defaultValue, resourceUri) : this.get(preferenceName, defaultValue);
        // eslint-disable-next-line no-null/no-null
        if (value === null || value === undefined) {
            return defaultValue;
        }
        return value.toString();
    }

    getNumber(preferenceName: string): number | undefined;
    getNumber(preferenceName: string, defaultValue: number): number;
    getNumber(preferenceName: string, defaultValue: number, resourceUri: string): number;
    getNumber(preferenceName: string, defaultValue?: number, resourceUri?: string): number | undefined {
        const value = resourceUri ? this.get(preferenceName, defaultValue, resourceUri) : this.get(preferenceName, defaultValue);
        // eslint-disable-next-line no-null/no-null
        if (value === null || value === undefined) {
            return defaultValue;
        }
        if (typeof value === 'number') {
            return value;
        }
        return Number(value);
    }

    inspect<T extends JSONValue>(preferenceName: string, resourceUri?: string, forceLanguageOverride?: boolean): PreferenceInspection<T> | undefined {
        const defaultValue = this.inspectInScope<T>(preferenceName, PreferenceScope.Default, resourceUri, forceLanguageOverride);
        const globalValue = this.inspectInScope<T>(preferenceName, PreferenceScope.User, resourceUri, forceLanguageOverride);
        const workspaceValue = this.inspectInScope<T>(preferenceName, PreferenceScope.Workspace, resourceUri, forceLanguageOverride);
        const workspaceFolderValue = this.inspectInScope<T>(preferenceName, PreferenceScope.Folder, resourceUri, forceLanguageOverride);

        const valueApplied = workspaceFolderValue ?? workspaceValue ?? globalValue ?? defaultValue;

        return { preferenceName, defaultValue, globalValue, workspaceValue, workspaceFolderValue, value: valueApplied };
    }

    inspectInScope<T extends JSONValue>(preferenceName: string, scope: PreferenceScope, resourceUri?: string, forceLanguageOverride?: boolean): T | undefined {
        const value = this.doInspectInScope<T>(preferenceName, scope, resourceUri);
        if (value === undefined && !forceLanguageOverride) {
            const overridden = this.overriddenPreferenceName(preferenceName);
            if (overridden) {
                return this.doInspectInScope(overridden.preferenceName, scope, resourceUri);
            }
        }
        return value;
    }

    protected getScopedValueFromInspection<T>(inspection: PreferenceInspection<T>, scope: PreferenceScope): T | undefined {
        switch (scope) {
            case PreferenceScope.Default:
                return inspection.defaultValue;
            case PreferenceScope.User:
                return inspection.globalValue;
            case PreferenceScope.Workspace:
                return inspection.workspaceValue;
            case PreferenceScope.Folder:
                return inspection.workspaceFolderValue;
        }
        unreachable(scope, 'Not all PreferenceScope enum variants handled.');
    }

    async updateValue(preferenceName: string, value: any, resourceUri?: string): Promise<void> {
        const inspection = this.inspect<any>(preferenceName, resourceUri);
        if (inspection) {
            const scopesToChange = this.getScopesToChange(inspection, value);
            const isDeletion = value === undefined
                || (
                    scopesToChange.length === 1
                    && scopesToChange[0] === PreferenceScope.User
                    && PreferenceUtils.deepEqual(value, inspection.defaultValue)
                );
            const effectiveValue = isDeletion ? undefined : value;
            await Promise.all(scopesToChange.map(scope => this.set(preferenceName, effectiveValue, scope, resourceUri)));
        }
    }

    protected getScopesToChange(inspection: PreferenceInspection<any>, intendedValue: any): PreferenceScope[] {
        if (PreferenceUtils.deepEqual(inspection.value, intendedValue)) {
            return [];
        }

        // Scopes in ascending order of scope breadth.
        const allScopes = [...this.schemaService.validScopes].reverse();
        // Get rid of Default scope. We can't set anything there.
        allScopes.pop();

        const isScopeDefined = (scope: PreferenceScope) => this.getScopedValueFromInspection(inspection, scope) !== undefined;

        if (intendedValue === undefined) {
            return allScopes.filter(isScopeDefined);
        }

        return [allScopes.find(isScopeDefined) ?? PreferenceScope.User];
    }

    overridePreferenceName(options: OverridePreferenceName): string {
        return this.preferenceOverrideService.overridePreferenceName(options);
    }
    overriddenPreferenceName(preferenceName: string): OverridePreferenceName | undefined {
        return this.preferenceOverrideService.overriddenPreferenceName(preferenceName);
    }

    protected doHas(preferenceName: string, resourceUri?: string): boolean {
        return this.doGet(preferenceName, undefined, resourceUri) !== undefined;
    }
    protected doInspectInScope<T>(preferenceName: string, scope: PreferenceScope, resourceUri?: string): T | undefined {
        const provider = this.getProvider(scope);
        return provider && provider.get<T>(preferenceName, resourceUri);
    }
    protected doGet<T>(preferenceName: string, defaultValue?: T, resourceUri?: string): T | undefined {
        return this.doResolve(preferenceName, defaultValue, resourceUri).value;
    }
    protected doResolve<T>(preferenceName: string, defaultValue?: T, resourceUri?: string): PreferenceResolveResult<T> {
        const result: PreferenceResolveResult<T> = {};
        for (const scope of this.schemaService.validScopes) {
            const provider = this.getProvider(scope);
            if (provider?.canHandleScope(scope)) {
                const { configUri, value } = provider.resolve<T>(preferenceName, resourceUri);
                if (value !== undefined) {
                    result.configUri = configUri;
                    result.value = PreferenceUtils.merge(result.value as any, value as any) as any;
                }
            }
        }
        return {
            configUri: result.configUri,
            value: result.value !== undefined ? deepFreeze(result.value) : defaultValue
        };
    }

    getConfigUri(scope: PreferenceScope, resourceUri?: string, sectionName: string = this.configurations.getConfigName()): URI | undefined {
        const provider = this.getProvider(scope);
        if (!provider || !this.configurations.isAnyConfig(sectionName)) {
            return undefined;
        }
        const configUri = provider.getConfigUri && provider.getConfigUri(resourceUri, sectionName);
        if (configUri) {
            return configUri;
        }
        return provider.getContainingConfigUri && provider.getContainingConfigUri(resourceUri, sectionName);
    }
}