/**
 * This file is distributed under the MIT License. See LICENSE.md for details.
 */

import * as yaml from "yaml";

export const yamlParseOptions = {
    strict: false,
    logLevel: "silent",
    intAsBigInt: true,
} as const;

export const yamlOutParseOptions = {
    keepUndefined: false,
} as const;

export const yamlToStringOptions = {
    doubleQuotedAsJSON: false,
    defaultKeyType: yaml.Scalar.PLAIN,
    defaultStringType: yaml.Scalar.QUOTE_DOUBLE,
    directives: true,
    lineWidth: 0,
} as const;

export type IReference = string;

/**
 * Reference class
 * Represents a pointer to another element of the Tuple Tree, which can be fetched via 'resolve'
 */
export class Reference<T, M> {
    reference: string;

    constructor(ref: string) {
        this.reference = ref;
    }

    toJSON(): string {
        return this.reference;
    }

    toString(): string {
        return this.reference;
    }

    equals(other: unknown): boolean {
        if (other instanceof Reference<T, M>) {
            return this.reference == other.reference;
        } else {
            return false;
        }
    }

    resolve(root: M): T | undefined {
        return _getElementByPath<T>(this.reference, root);
    }

    isValid(): boolean {
        return this.reference !== "";
    }

    static parse<T, M>(ref?: string): Reference<T, M> {
        return new Reference(ref || "");
    }
}

/**
 * Generate a random hexadecimal string
 * @param length output string length
 * @returns a random string
 */
function randomBytes(length: number): string {
    let value = "";
    for (let i = 0; i < length; i++) {
        value += (Math.random() * 16).toString(16);
    }
    return value;
}

/**
 * Generate a random bigint, between [start, end)
 * @param start lower bound
 * @param end upper bound
 * @returns random bigint
 */
function randomBigint(start: bigint, end: bigint): bigint {
    const diff = end - start;
    let value = end;
    do {
        const randomLength = diff.toString().length * Math.random();
        value = BigInt(`0x${randomBytes(randomLength)}`);
    } while (value > diff);
    return value + start;
}

/**
 * Utility function that returns a bigint suitable for IDs
 * @returns guid ID
 */
export function genGuid(): bigint {
    return randomBigint(2n ** 10n + 1n, 2n ** 64n - 1n);
}

// Tree traversal

function getElementByPathArray<T>(path: string[], obj: any): T | undefined {
    if (obj === undefined) {
        return undefined;
    }

    let component = path[0];
    if (obj instanceof Array) {
        for (const elem of obj) {
            if (keyableObject(elem) && elem.key() == component) {
                if (path.length == 1) {
                    return elem as unknown as T;
                } else {
                    return getElementByPathArray(path.slice(1), elem);
                }
            }
        }
        return undefined;
    } else {
        if (component.includes("::")) {
            const parts = component.split("::", 2);
            component = parts[1];
            if (obj.Kind !== parts[0]) {
                return undefined;
            }
        }
        if (component in obj) {
            if (path.length == 1) {
                return obj[component];
            } else {
                return getElementByPathArray(path.slice(1), obj[component]);
            }
        } else {
            return undefined;
        }
    }
}

function setElementByPathArray<T>(path: string[], obj: any, value: T): boolean {
    if (obj === undefined) {
        return false;
    }

    let component = path[0];
    if (obj instanceof Array) {
        const index = obj.findIndex((elem) => keyableObject(elem) && elem.key() === component);

        if (index >= 0) {
            if (path.length === 1) {
                obj[index] = value;
                return true;
            } else {
                return setElementByPathArray(path.slice(1), obj[index], value);
            }
        } else if (
            index === -1 &&
            path.length === 1 &&
            keyableObject(value) &&
            value.key() === component
        ) {
            // We're appending a value to an array
            obj.push(value);
            return true;
        } else {
            return false;
        }
    } else {
        if (component.includes("::")) {
            const parts = component.split("::", 2);
            component = parts[1];
            if (obj.Kind !== parts[0]) {
                return false;
            }
        }
        if (component in obj) {
            if (path.length == 1) {
                obj[component] = value;
                return true;
            } else {
                return setElementByPathArray(path.slice(1), obj[component], value);
            }
        }
        return false;
    }
}

/**
 * Given a Tuple Tree path and a root object, resolve the object or return
 * undefined if the path is not present in the tuple tree
 */
export function _getElementByPath<T>(path: string, obj: any): T | undefined {
    return getElementByPathArray(path.split("/").slice(1), obj);
}

/**
 * Given a Tuple Tree path, a root object and a value, set the path with the
 * value provided and return true. If the path does not resolve, this returns
 * false
 */
export function _setElementByPath<T>(path: string, obj: any, value: T): boolean {
    return setElementByPathArray(path.split("/").slice(1), obj, value);
}

// Tree Diffing

interface IDiffSet {
    Changes: IDiff[];
}

export class DiffSet {
    Changes: Diff[];

    constructor(Changes: Diff[]) {
        this.Changes = Changes;
    }

    static parse(rawObject: IDiffSet): DiffSet {
        return new DiffSet(rawObject.Changes.map((e) => new Diff(e.Path, e.Add, e.Remove)));
    }

    toJSON(): IDiffSet {
        return {
            Changes: this.Changes.filter((e) => e.isValid()).map((e) => e.toJSON()),
        };
    }

    reversed(): DiffSet {
        return new DiffSet(this.Changes.map((e) => new Diff(e.Path, e.Remove, e.Add)));
    }

    static deserialize(input: string): DiffSet {
        return DiffSet.parse(yaml.parse(input));
    }

    serialize(): string {
        const doc = new yaml.Document(this, yamlOutParseOptions);
        return doc.toString(yamlToStringOptions);
    }
}

interface IDiff {
    Path: string;
    Add?: any;
    Remove?: any;
}

class Diff {
    Path: string;
    Add: any;
    Remove: any;

    constructor(Path: string, Add: any, Remove: any) {
        this.Path = Path;
        this.Add = Add;
        this.Remove = Remove;
    }

    toJSON(): IDiff {
        let ret = { Path: this.Path };
        if (this.Add !== undefined) {
            ret["Add"] = this.Add;
        }
        if (this.Remove !== undefined) {
            ret["Remove"] = this.Remove;
        }
        return ret;
    }

    isValid(): boolean {
        return this.Add !== undefined || this.Remove !== undefined;
    }
}

function isNull(obj: any): obj is undefined | null {
    return obj === undefined || obj === null;
}

function hasEquals(obj: any): obj is { equals: (other: unknown) => boolean } {
    return typeof obj === "object" && typeof obj?.equals === "function";
}

function keyableObject(obj: any): obj is { key: () => string } {
    return (
        obj !== null &&
        typeof obj === "object" &&
        "key" in obj &&
        typeof obj.key === "function" &&
        typeof obj.key() === "string"
    );
}

export function _makeDiff<T>(
    tuple_tree_old: T,
    tuple_tree_new: T,
    typesMetadata: TypesMetadata,
    rootType: Constructor
): DiffSet {
    const rootTypeInfo: ConstructorType = {
        type: rootType,
        ctor: "class",
        isArray: false,
        isAbstract: false,
    };
    return new DiffSet(
        makeDiffSubtree(tuple_tree_old, tuple_tree_new, "", typesMetadata, rootTypeInfo, false)
    );
}

export function makeDiffSubtree(
    obj_old: any,
    obj_new: any,
    prefix: string,
    typesMetadata: TypesMetadata,
    typeInfo: TypeInfo,
    inArray: boolean
): Diff[] {
    const result: Diff[] = [];
    if (typeof obj_old != typeof obj_new) {
        return [];
    }

    let infoObject: TypeInfoObject;
    let upcast = false;
    if (typeInfo.isAbstract) {
        const derivedClass = (
            typeInfo.type as unknown as { parseClass: (obj) => Constructor | undefined }
        ).parseClass(obj_old);
        const baseInfoObject = typesMetadata.get(typeInfo.type as Constructor | Parsable);
        if (derivedClass !== undefined) {
            const derivedClassObject = typesMetadata.get(derivedClass);
            infoObject = { ...baseInfoObject, ...derivedClassObject };
            upcast = true;
        } else {
            infoObject = { ...baseInfoObject };
        }
    } else {
        infoObject = typesMetadata.get(typeInfo.type as Constructor | Parsable);
    }

    if (typeInfo.isArray && !inArray) {
        if ("keyed" in typeInfo.type && typeInfo.type.keyed) {
            const map_old = new Map(obj_old.map((e) => [e.key(), e]));
            const map_new = new Map(obj_new.map((e) => [e.key(), e]));

            const common_keys = new Set();
            for (const [key, value] of map_old) {
                if (map_new.has(key)) {
                    common_keys.add(key);
                    result.push(
                        ...makeDiffSubtree(
                            value,
                            map_new.get(key),
                            `${prefix}/${key}`,
                            typesMetadata,
                            typeInfo,
                            true
                        )
                    );
                } else {
                    result.push(new Diff(prefix, undefined, value));
                }
            }

            for (const [key, value] of map_new) {
                if (!common_keys.has(key)) {
                    result.push(new Diff(prefix, value, undefined));
                }
            }
        } else {
            const array_old: Array<any> = [...obj_old];
            const array_new: Array<any> = [...obj_new];
            array_old.sort();
            array_new.sort();
            while (array_old.length > 0) {
                const head = array_old.shift();
                const new_idx = array_new.indexOf(head);
                if (new_idx !== -1) {
                    array_new.splice(new_idx, 1);
                } else {
                    result.push(new Diff(prefix, undefined, head));
                }
            }
            result.push(...array_new.map((e) => new Diff(prefix, e, undefined)));
        }
    } else {
        for (const key in infoObject) {
            const key_prefix = `${prefix}/` + (upcast ? `${obj_old.Kind}::${key}` : key);
            if (obj_old[key] === undefined && obj_new[key] !== undefined) {
                result.push(new Diff(`${prefix}/${key}`, obj_new[key].toJSON(), undefined));
            } else if (obj_old[key] !== undefined && obj_new[key] === undefined) {
                result.push(new Diff(`${prefix}/${key}`, undefined, obj_old[key].toJSON()));
            } else if (obj_old[key] === undefined && obj_new[key] === undefined) {
                // No changes, do nothing
            } else if (
                (infoObject[key].ctor == "native" || infoObject[key].ctor == "enum") &&
                !infoObject[key].isArray
            ) {
                if (obj_old[key] !== obj_new[key]) {
                    result.push(
                        new Diff(key_prefix, obj_new[key].toString(), obj_old[key].toString())
                    );
                }
            } else if (hasEquals(obj_old[key]) && hasEquals(obj_new[key])) {
                if (!obj_old[key].equals(obj_new[key])) {
                    result.push(
                        new Diff(key_prefix, obj_new[key].toString(), obj_old[key].toString())
                    );
                }
            } else {
                result.push(
                    ...makeDiffSubtree(
                        obj_old[key],
                        obj_new[key],
                        key_prefix,
                        typesMetadata,
                        infoObject[key],
                        false
                    )
                );
            }
        }
    }
    return result;
}

function constructType<T>(typeInfo: TypeInfo, data: any): T {
    switch (typeInfo.ctor) {
        case "class":
            return new typeInfo.type(data);
        case "parse":
            return typeInfo.type.parse(data);
        case "enum":
        case "native":
            return typeInfo.type(data);
    }
}

type getTypeInfoType = (path: string | string[], root?: any) => TypeInfo;
export function _getTypeInfo(
    path: string | string[],
    root: any,
    typesMetadata: TypesMetadata
): TypeInfo | undefined {
    if (typeof path === "string") {
        path = path.split("/").slice(1);
    }

    let component = path[0];
    if (component.includes("::")) {
        const parts = component.split("::", 2);
        component = parts[1];
    }

    const root_hint = typesMetadata.get(root);
    if (root_hint !== undefined && component in root_hint) {
        const type_info = root_hint[component];
        if (path.length === 1) {
            return type_info;
        } else {
            if (type_info.isArray && type_info.ctor === "parse" && "parseKey" in type_info.type) {
                const key = path[1];
                const key_parsed = type_info.type.parseKey(key);
                if ("Kind" in key_parsed) {
                    const specialized_type = Array.from(typesMetadata.keys()).find(
                        (e) => "name" in e && e["name"] === key_parsed.Kind
                    );
                    return _getTypeInfo(path.slice(2), specialized_type, typesMetadata);
                }
                return _getTypeInfo(path.slice(2), type_info.type, typesMetadata);
            } else {
                return _getTypeInfo(
                    path.slice(type_info.isArray ? 2 : 1),
                    type_info.type,
                    typesMetadata
                );
            }
        }
    }
    return undefined;
}

function getParentElementByPath<T>(path: string, obj: any): T | undefined {
    const parentPath = path.split("/").slice(1, -1);
    if (parentPath.length > 1) {
        return _getElementByPath(`/${parentPath.join("/")}`, obj);
    } else {
        return obj;
    }
}

export function _validateDiff<T>(obj: T, diffs: DiffSet, getTypeInfo: getTypeInfoType): boolean {
    for (const diff of diffs.Changes) {
        const target = _getElementByPath(diff.Path, obj);
        const info = getTypeInfo(diff.Path);
        if (info.isArray) {
            if (diff.Remove !== undefined) {
                if (target instanceof Array) {
                    const array_target = target.find(
                        (e) => yaml.stringify(e) === yaml.stringify(diff.Remove)
                    );
                    if (array_target === undefined) {
                        return false;
                    }
                } else {
                    return false;
                }
            }
            if (diff.Add !== undefined && target instanceof Array) {
                const array_target = target.find(
                    (e) => yaml.stringify(e) === yaml.stringify(diff.Add)
                );
                if (array_target !== undefined) {
                    return false;
                }
            }
        } else {
            if (
                diff.Remove !== undefined &&
                yaml.stringify(target) !== yaml.stringify(diff.Remove)
            ) {
                return false;
            }
            if (diff.Add !== undefined && diff.Remove === undefined && !isNull(target)) {
                return false;
            }
        }
    }
    return true;
}

export function _applyDiff<T>(
    obj: T,
    diffs: DiffSet,
    validateDiff: (obj: T, diffs: DiffSet) => boolean,
    getTypeInfo: getTypeInfoType,
    clone: (obj: T) => T
): [false] | [true, T] {
    if (!validateDiff(obj, diffs)) {
        return [false];
    }
    const new_obj = clone(obj);
    for (const diff of diffs.Changes) {
        let target = _getElementByPath(diff.Path, new_obj);
        const info = getTypeInfo(diff.Path);
        if (target instanceof Array) {
            if (diff.Remove !== undefined) {
                const idx = target.findIndex(
                    (e) => yaml.stringify(e) === yaml.stringify(diff.Remove)
                );
                target.splice(idx, 1);
            }

            if (diff.Add !== undefined) {
                (target as any).push(constructType(info, diff.Add));
            }
        } else {
            const parent = getParentElementByPath(diff.Path, new_obj)!;
            const element = diff.Path.split("/").reverse()[0];
            true;
            if (diff.Remove !== undefined) {
                parent[element] = undefined;
            }
            if (diff.Add !== undefined && diff.Add !== "") {
                parent[element] = constructType(info, diff.Add);
            }
        }
    }

    return [true, new_obj];
}

// Type Hinting

type Constructor = new (rawObject: any) => any;
type SimpleParsable = { parse: (rawObject: any) => any };
type Parsable = SimpleParsable | (SimpleParsable & { parseKey: (key: string) => any });
type NativeParsable = (rawObject: any) => any;

export type TupleTreeType = Constructor | Parsable;

interface CommonTypeInfo {
    isArray: boolean;
    isAbstract: boolean;
}

interface ConstructorType extends CommonTypeInfo {
    type: Constructor;
    ctor: "class";
}

interface ParsableType extends CommonTypeInfo {
    type: Parsable;
    ctor: "parse";
}

interface NativeType extends CommonTypeInfo {
    type: NativeParsable;
    ctor: "native";
}

interface EnumDefinition extends CommonTypeInfo {
    type: NativeParsable;
    ctor: "enum";
    possibleValues: readonly string[];
}

export type TypeInfo = ConstructorType | ParsableType | NativeType | EnumDefinition;
export type TypeInfoObject = { [key: string]: TypeInfo };
export type TypesMetadata = Map<TupleTreeType, TypeInfoObject>;

export function BigIntBuilder(rawObject: any): bigint {
    return BigInt(rawObject);
}