/** @internal */
namespace ts.classifier.v2020 {

    export const enum TokenEncodingConsts {
        typeOffset = 8,
        modifierMask = (1 << typeOffset) - 1
    }

    export const enum TokenType {
        class, enum, interface, namespace, typeParameter, type, parameter, variable, enumMember, property, function, member
    }

    export const enum TokenModifier {
        declaration, static, async, readonly, defaultLibrary, local
    }

    /** This is mainly used internally for testing */
    export function getSemanticClassifications(program: Program, cancellationToken: CancellationToken, sourceFile: SourceFile, span: TextSpan): ClassifiedSpan2020[] {
        const classifications = getEncodedSemanticClassifications(program, cancellationToken, sourceFile, span);

        Debug.assert(classifications.spans.length % 3 === 0);
        const dense = classifications.spans;
        const result: ClassifiedSpan2020[] = [];
        for (let i = 0; i < dense.length; i += 3) {
            result.push({
                textSpan: createTextSpan(dense[i], dense[i + 1]),
                classificationType: dense[i + 2]
            });
        }

        return result;
    }

    export function getEncodedSemanticClassifications(program: Program, cancellationToken: CancellationToken, sourceFile: SourceFile, span: TextSpan): Classifications {
        return {
            spans: getSemanticTokens(program, sourceFile, span, cancellationToken),
            endOfLineState: EndOfLineState.None
        };
    }

    function getSemanticTokens(program: Program, sourceFile: SourceFile, span: TextSpan, cancellationToken: CancellationToken): number[] {
        const resultTokens: number[] = [];

        const collector = (node: Node, typeIdx: number, modifierSet: number) => {
            resultTokens.push(node.getStart(sourceFile), node.getWidth(sourceFile), ((typeIdx + 1) << TokenEncodingConsts.typeOffset) + modifierSet);
        };

        if (program && sourceFile) {
            collectTokens(program, sourceFile, span, collector, cancellationToken);
        }
        return resultTokens;
    }

    function collectTokens(program: Program, sourceFile: SourceFile, span: TextSpan, collector: (node: Node, tokenType: number, tokenModifier: number) => void, cancellationToken: CancellationToken) {
        const typeChecker = program.getTypeChecker();

        let inJSXElement = false;

        function visit(node: Node) {
            switch(node.kind) {
                case SyntaxKind.ModuleDeclaration:
                case SyntaxKind.ClassDeclaration:
                case SyntaxKind.InterfaceDeclaration:
                case SyntaxKind.FunctionDeclaration:
                case SyntaxKind.ClassExpression:
                case SyntaxKind.FunctionExpression:
                case SyntaxKind.ArrowFunction:
                    cancellationToken.throwIfCancellationRequested();
            }

            if (!node || !textSpanIntersectsWith(span, node.pos, node.getFullWidth()) || node.getFullWidth() === 0) {
                return;
            }
            const prevInJSXElement = inJSXElement;
            if (isJsxElement(node) || isJsxSelfClosingElement(node)) {
                inJSXElement = true;
            }
            if (isJsxExpression(node)) {
                inJSXElement = false;
            }

            if (isIdentifier(node) && !inJSXElement && !inImportClause(node) && !isInfinityOrNaNString(node.escapedText)) {
                let symbol = typeChecker.getSymbolAtLocation(node);
                if (symbol) {
                    if (symbol.flags & SymbolFlags.Alias) {
                        symbol = typeChecker.getAliasedSymbol(symbol);
                    }
                    let typeIdx = classifySymbol(symbol, getMeaningFromLocation(node));
                    if (typeIdx !== undefined) {
                        let modifierSet = 0;
                        if (node.parent) {
                            const parentIsDeclaration = (isBindingElement(node.parent) || tokenFromDeclarationMapping.get(node.parent.kind) === typeIdx);
                            if (parentIsDeclaration && (node.parent as NamedDeclaration).name === node) {
                                modifierSet = 1 << TokenModifier.declaration;
                            }
                        }

                        // property declaration in constructor
                        if (typeIdx === TokenType.parameter && isRightSideOfQualifiedNameOrPropertyAccess(node)) {
                            typeIdx = TokenType.property;
                        }

                        typeIdx = reclassifyByType(typeChecker, node, typeIdx);

                        const decl = symbol.valueDeclaration;
                        if (decl) {
                            const modifiers = getCombinedModifierFlags(decl);
                            const nodeFlags = getCombinedNodeFlags(decl);
                            if (modifiers & ModifierFlags.Static) {
                                modifierSet |= 1 << TokenModifier.static;
                            }
                            if (modifiers & ModifierFlags.Async) {
                                modifierSet |= 1 << TokenModifier.async;
                            }
                            if (typeIdx !== TokenType.class && typeIdx !== TokenType.interface) {
                                if ((modifiers & ModifierFlags.Readonly) || (nodeFlags & NodeFlags.Const) || (symbol.getFlags() & SymbolFlags.EnumMember)) {
                                    modifierSet |= 1 << TokenModifier.readonly;
                                }
                            }
                            if ((typeIdx === TokenType.variable || typeIdx === TokenType.function) && isLocalDeclaration(decl, sourceFile)) {
                                modifierSet |= 1 << TokenModifier.local;
                            }
                            if (program.isSourceFileDefaultLibrary(decl.getSourceFile())) {
                                modifierSet |= 1 << TokenModifier.defaultLibrary;
                            }
                        }
                        else if (symbol.declarations && symbol.declarations.some(d => program.isSourceFileDefaultLibrary(d.getSourceFile()))) {
                            modifierSet |= 1 << TokenModifier.defaultLibrary;
                        }

                        collector(node, typeIdx, modifierSet);

                    }
                }
            }
            forEachChild(node, visit);

            inJSXElement = prevInJSXElement;
        }
        visit(sourceFile);
    }

    function classifySymbol(symbol: Symbol, meaning: SemanticMeaning): TokenType | undefined {
        const flags = symbol.getFlags();
        if (flags & SymbolFlags.Class) {
            return TokenType.class;
        }
        else if (flags & SymbolFlags.Enum) {
            return TokenType.enum;
        }
         else if (flags & SymbolFlags.TypeAlias) {
            return TokenType.type;
        }
        else if (flags & SymbolFlags.Interface) {
            if (meaning & SemanticMeaning.Type) {
                return TokenType.interface;
            }
        }
        else if (flags & SymbolFlags.TypeParameter) {
            return TokenType.typeParameter;
        }
        let decl = symbol.valueDeclaration || symbol.declarations && symbol.declarations[0];
        if (decl && isBindingElement(decl)) {
            decl = getDeclarationForBindingElement(decl);
        }
        return decl && tokenFromDeclarationMapping.get(decl.kind);
    }

    function reclassifyByType(typeChecker: TypeChecker, node: Node, typeIdx: TokenType): TokenType {
        // type based classifications
        if (typeIdx === TokenType.variable || typeIdx === TokenType.property || typeIdx === TokenType.parameter) {
            const type = typeChecker.getTypeAtLocation(node);
            if (type) {
                const test = (condition: (type: Type) => boolean) => {
                    return condition(type) || type.isUnion() && type.types.some(condition);
                };
                if (typeIdx !== TokenType.parameter && test(t => t.getConstructSignatures().length > 0)) {
                    return TokenType.class;
                }
                if (test(t => t.getCallSignatures().length > 0) && !test(t => t.getProperties().length > 0) || isExpressionInCallExpression(node)) {
                    return typeIdx === TokenType.property ? TokenType.member : TokenType.function;
                }
            }
        }
        return typeIdx;
    }

    function isLocalDeclaration(decl: Declaration, sourceFile: SourceFile): boolean {
        if (isBindingElement(decl)) {
            decl = getDeclarationForBindingElement(decl);
        }
        if (isVariableDeclaration(decl)) {
            return (!isSourceFile(decl.parent.parent.parent) || isCatchClause(decl.parent)) && decl.getSourceFile() === sourceFile;
        }
        else if (isFunctionDeclaration(decl)) {
            return !isSourceFile(decl.parent) && decl.getSourceFile() === sourceFile;
        }
        return false;
    }

    function getDeclarationForBindingElement(element: BindingElement): VariableDeclaration | ParameterDeclaration {
        while (true) {
            if (isBindingElement(element.parent.parent)) {
                element = element.parent.parent;
            }
            else {
                return element.parent.parent;
            }
        }
    }

    function inImportClause(node: Node): boolean {
        const parent = node.parent;
        return parent && (isImportClause(parent) || isImportSpecifier(parent) || isNamespaceImport(parent));
    }

    function isExpressionInCallExpression(node: Node): boolean {
        while (isRightSideOfQualifiedNameOrPropertyAccess(node)) {
            node = node.parent;
        }
        return isCallExpression(node.parent) && node.parent.expression === node;
    }

    function isRightSideOfQualifiedNameOrPropertyAccess(node: Node): boolean {
        return (isQualifiedName(node.parent) && node.parent.right === node) || (isPropertyAccessExpression(node.parent) && node.parent.name === node);
    }

    const tokenFromDeclarationMapping = new Map<SyntaxKind, TokenType>([
        [SyntaxKind.VariableDeclaration, TokenType.variable],
        [SyntaxKind.Parameter, TokenType.parameter],
        [SyntaxKind.PropertyDeclaration, TokenType.property],
        [SyntaxKind.ModuleDeclaration, TokenType.namespace],
        [SyntaxKind.EnumDeclaration, TokenType.enum],
        [SyntaxKind.EnumMember, TokenType.enumMember],
        [SyntaxKind.ClassDeclaration, TokenType.class],
        [SyntaxKind.MethodDeclaration, TokenType.member],
        [SyntaxKind.FunctionDeclaration, TokenType.function],
        [SyntaxKind.FunctionExpression, TokenType.function],
        [SyntaxKind.MethodSignature, TokenType.member],
        [SyntaxKind.GetAccessor, TokenType.property],
        [SyntaxKind.SetAccessor, TokenType.property],
        [SyntaxKind.PropertySignature, TokenType.property],
        [SyntaxKind.InterfaceDeclaration, TokenType.interface],
        [SyntaxKind.TypeAliasDeclaration, TokenType.type],
        [SyntaxKind.TypeParameter, TokenType.typeParameter],
        [SyntaxKind.PropertyAssignment, TokenType.property],
        [SyntaxKind.ShorthandPropertyAssignment, TokenType.property]
    ]);
}