import * as tsutils from "tsutils/typeguard/3.0";
import ts from "typescript";
import { sliceSet } from "./utils";
import type { VisitorContext } from "./visitor-context";
import * as VisitorIsNumber from "./visitor-is-number";
import * as VisitorIsString from "./visitor-is-string";
import * as VisitorTypeCheck from "./visitor-type-check";
import * as VisitorTypeName from "./visitor-type-name";
import * as VisitorUtils from "./visitor-utils";

function visitRegularObjectType(
	type: ts.ObjectType,
	indexType: ts.Type,
	visitorContext: VisitorContext,
) {
	const name = VisitorTypeName.visitType(type, visitorContext, {
		type: "indexed-access",
		indexType,
	});
	return VisitorUtils.setFunctionIfNotExists(name, visitorContext, () => {
		// TODO: check property index
		// const stringIndexType = visitorContext.checker.getIndexTypeOfType(type, ts.IndexKind.String);

		const properties = visitorContext.checker.getPropertiesOfType(type);
		const propertiesInfo = properties.map((property) =>
			VisitorUtils.getPropertyInfo(type, property, visitorContext),
		);
		const stringType = VisitorIsString.visitType(indexType, visitorContext);
		if (typeof stringType === "boolean") {
			if (!stringType) {
				throw new Error(
					"A non-string type was used to index an object type.",
				);
			}
			const functionNames = propertiesInfo.map((propertyInfo) =>
				propertyInfo.isMethod
					? VisitorUtils.getIgnoredTypeFunction(visitorContext)
					: VisitorTypeCheck.visitType(
							propertyInfo.type!,
							visitorContext,
					  ),
			);
			return VisitorUtils.createDisjunctionFunction(
				functionNames,
				name,
				visitorContext,
			);
		} else {
			const strings = sliceSet(stringType);
			if (
				strings.some((value) =>
					propertiesInfo.every(
						(propertyInfo) => propertyInfo.name !== value,
					),
				)
			) {
				throw new Error(
					"Indexed access on object type with an index that does not exist.",
				);
			}
			const stringPropertiesInfo = strings.map(
				(value) =>
					propertiesInfo.find(
						(propertyInfo) => propertyInfo.name === value,
					)!,
			);
			const functionNames = stringPropertiesInfo.map((propertyInfo) =>
				propertyInfo.isMethod
					? VisitorUtils.getIgnoredTypeFunction(visitorContext)
					: VisitorTypeCheck.visitType(
							propertyInfo.type!,
							visitorContext,
					  ),
			);
			return VisitorUtils.createDisjunctionFunction(
				functionNames,
				name,
				visitorContext,
			);
		}
	});
}

function visitTupleObjectType(
	type: ts.TupleType,
	indexType: ts.Type,
	visitorContext: VisitorContext,
) {
	const name = VisitorTypeName.visitType(type, visitorContext, {
		type: "indexed-access",
		indexType,
	});
	return VisitorUtils.setFunctionIfNotExists(name, visitorContext, () => {
		if (type.typeArguments === undefined) {
			throw new Error("Expected tuple type to have type arguments.");
		}
		const numberType = VisitorIsNumber.visitType(indexType, visitorContext);
		if (typeof numberType === "boolean") {
			if (!numberType) {
				throw new Error(
					"A non-number type was used to index a tuple type.",
				);
			}
			const functionNames = type.typeArguments.map((type) =>
				VisitorTypeCheck.visitType(type, visitorContext),
			);
			return VisitorUtils.createDisjunctionFunction(
				functionNames,
				name,
				visitorContext,
			);
		} else {
			const numbers = sliceSet(numberType);
			if (numbers.some((value) => value >= type.typeArguments!.length)) {
				throw new Error(
					"Indexed access on tuple type exceeds length of tuple.",
				);
			}
			const functionNames = numbers.map((value) =>
				VisitorTypeCheck.visitType(
					type.typeArguments![value],
					visitorContext,
				),
			);
			return VisitorUtils.createDisjunctionFunction(
				functionNames,
				name,
				visitorContext,
			);
		}
	});
}

function visitArrayObjectType(
	type: ts.ObjectType,
	indexType: ts.Type,
	visitorContext: VisitorContext,
) {
	const numberIndexType = visitorContext.checker.getIndexTypeOfType(
		type,
		ts.IndexKind.Number,
	);
	if (numberIndexType === undefined) {
		throw new Error(
			"Expected array ObjectType to have a number index type.",
		);
	}
	const numberType = VisitorIsNumber.visitType(indexType, visitorContext);
	if (numberType !== false) {
		return VisitorTypeCheck.visitType(numberIndexType, visitorContext);
	} else {
		throw new Error("A non-number type was used to index an array type.");
	}
}

function visitObjectType(
	type: ts.ObjectType,
	indexType: ts.Type,
	visitorContext: VisitorContext,
) {
	if (tsutils.isTupleType(type)) {
		// Tuple with finite length.
		return visitTupleObjectType(type, indexType, visitorContext);
	} else if (
		visitorContext.checker.getIndexTypeOfType(type, ts.IndexKind.Number)
	) {
		// Index type is number -> array type.
		return visitArrayObjectType(type, indexType, visitorContext);
	} else {
		// Index type is string -> regular object type.
		return visitRegularObjectType(type, indexType, visitorContext);
	}
}

function visitUnionOrIntersectionType(
	type: ts.UnionOrIntersectionType,
	indexType: ts.Type,
	visitorContext: VisitorContext,
) {
	const name = VisitorTypeName.visitType(type, visitorContext, {
		type: "indexed-access",
		indexType,
	});
	return VisitorUtils.setFunctionIfNotExists(name, visitorContext, () => {
		const functionNames = type.types.map((type) =>
			visitType(type, indexType, visitorContext),
		);
		if (tsutils.isUnionType(type)) {
			// (T | U)[I] = T[I] & U[I]
			return VisitorUtils.createConjunctionFunction(functionNames, name);
		} else {
			// (T & U)[I] = T[I] | U[I]
			return VisitorUtils.createDisjunctionFunction(
				functionNames,
				name,
				visitorContext,
			);
		}
	});
}

function visitIndexType(): string {
	// (keyof U)[T] is an error (actually it can be String.toString or String.valueOf but we don't support this edge case)
	throw new Error("Index types cannot be used as indexed types.");
}

function visitNonPrimitiveType(): string {
	// object[T] is an error
	throw new Error("Non-primitive object cannot be used as an indexed type.");
}

function visitLiteralType(): string {
	// 'string'[T] or 0xFF[T] is an error
	throw new Error(
		"Literal strings/numbers cannot be used as an indexed type.",
	);
}

function visitTypeReference(
	type: ts.TypeReference,
	indexType: ts.Type,
	visitorContext: VisitorContext,
) {
	const mapping: Map<ts.Type, ts.Type> = VisitorUtils.getTypeReferenceMapping(
		type,
		visitorContext,
	);
	const previousTypeReference = visitorContext.previousTypeReference;
	visitorContext.typeMapperStack.push(mapping);
	visitorContext.previousTypeReference = type;
	const result = visitType(type.target, indexType, visitorContext);
	visitorContext.previousTypeReference = previousTypeReference;
	visitorContext.typeMapperStack.pop();
	return result;
}

function visitTypeParameter(
	type: ts.Type,
	indexType: ts.Type,
	visitorContext: VisitorContext,
) {
	const mappedType = VisitorUtils.getResolvedTypeParameter(
		type,
		visitorContext,
	);
	if (mappedType === undefined) {
		throw new Error("Unbound type parameter, missing type node.");
	}
	return visitType(mappedType, indexType, visitorContext);
}

function visitBigInt(): string {
	// bigint[T] is an error
	throw new Error("BigInt cannot be used as an indexed type.");
}

function visitBoolean(): string {
	// boolean[T] is an error
	throw new Error("Boolean cannot be used as an indexed type.");
}

function visitString(): string {
	// string[T] is an error
	throw new Error("String cannot be used as an indexed type.");
}

function visitBooleanLiteral(): string {
	// true[T] or false[T] is an error
	throw new Error("True/false cannot be used as an indexed type.");
}

function visitNumber(): string {
	// number[T] is an error
	throw new Error("Number cannot be used as an indexed type.");
}

function visitUndefined(): string {
	// undefined[T] is an error
	throw new Error("Undefined cannot be used as an indexed type.");
}

function visitNull(): string {
	// null[T] is an error
	throw new Error("Null cannot be used as an indexed type.");
}

function visitNever(visitorContext: VisitorContext) {
	// never[T] = never
	return VisitorUtils.getNeverFunction(visitorContext);
}

function visitUnknown(visitorContext: VisitorContext) {
	// unknown[T] = unknown
	return VisitorUtils.getUnknownFunction(visitorContext);
}

function visitAny(visitorContext: VisitorContext) {
	// any[T] = any
	return VisitorUtils.getAnyFunction(visitorContext);
}

export function visitType(
	type: ts.Type,
	indexType: ts.Type,
	visitorContext: VisitorContext,
): string {
	if ((ts.TypeFlags.Any & type.flags) !== 0) {
		// Any
		return visitAny(visitorContext);
	} else if ((ts.TypeFlags.Unknown & type.flags) !== 0) {
		// Unknown
		return visitUnknown(visitorContext);
	} else if ((ts.TypeFlags.Never & type.flags) !== 0) {
		// Never
		return visitNever(visitorContext);
	} else if ((ts.TypeFlags.Null & type.flags) !== 0) {
		// Null
		return visitNull();
	} else if ((ts.TypeFlags.Undefined & type.flags) !== 0) {
		// Undefined
		return visitUndefined();
	} else if ((ts.TypeFlags.Number & type.flags) !== 0) {
		// Number
		return visitNumber();
	} else if (VisitorUtils.isBigIntType(type)) {
		// BigInt
		return visitBigInt();
	} else if ((ts.TypeFlags.Boolean & type.flags) !== 0) {
		// Boolean
		return visitBoolean();
	} else if ((ts.TypeFlags.String & type.flags) !== 0) {
		// String
		return visitString();
	} else if ((ts.TypeFlags.BooleanLiteral & type.flags) !== 0) {
		// Boolean literal (true/false)
		return visitBooleanLiteral();
	} else if (
		tsutils.isTypeReference(type) &&
		visitorContext.previousTypeReference !== type
	) {
		// Type references.
		return visitTypeReference(type, indexType, visitorContext);
	} else if ((ts.TypeFlags.TypeParameter & type.flags) !== 0) {
		// Type parameter
		return visitTypeParameter(type, indexType, visitorContext);
	} else if (tsutils.isObjectType(type)) {
		// Object type (including interfaces, arrays, tuples)
		return visitObjectType(type, indexType, visitorContext);
	} else if (tsutils.isLiteralType(type)) {
		// Literal string/number types ('foo')
		return visitLiteralType();
	} else if (tsutils.isUnionOrIntersectionType(type)) {
		// Union or intersection type (| or &)
		return visitUnionOrIntersectionType(type, indexType, visitorContext);
	} else if ((ts.TypeFlags.NonPrimitive & type.flags) !== 0) {
		// Non-primitive such as object
		return visitNonPrimitiveType();
	} else if ((ts.TypeFlags.Index & type.flags) !== 0) {
		// Index type: keyof T
		return visitIndexType();
	} else if (tsutils.isIndexedAccessType(type)) {
		// Indexed access type: T[U]
		// return visitIndexedAccessType(type, visitorContext);
		// TODO:
		throw new Error("Not yet implemented.");
	} else {
		throw new Error(
			`Could not generate type-check; unsupported type with flags: ${type.flags}`,
		);
	}
}