/* @internal */
namespace ts.JsDoc {
    const jsDocTagNames = [
        "augments",
        "author",
        "argument",
        "borrows",
        "class",
        "constant",
        "constructor",
        "constructs",
        "default",
        "deprecated",
        "description",
        "event",
        "example",
        "extends",
        "field",
        "fileOverview",
        "function",
        "ignore",
        "inner",
        "lends",
        "link",
        "memberOf",
        "name",
        "namespace",
        "param",
        "private",
        "property",
        "public",
        "requires",
        "returns",
        "see",
        "since",
        "static",
        "throws",
        "type",
        "typedef",
        "property",
        "prop",
        "version"
    ];
    let jsDocCompletionEntries: CompletionEntry[];

    export function getJsDocCommentsFromDeclarations(declarations: Declaration[]) {
        // Only collect doc comments from duplicate declarations once:
        // In case of a union property there might be same declaration multiple times
        // which only varies in type parameter
        // Eg. const a: Array<string> | Array<number>; a.length
        // The property length will have two declarations of property length coming
        // from Array<T> - Array<string> and Array<number>
        const documentationComment = <SymbolDisplayPart[]>[];
        forEachUnique(declarations, declaration => {
            const comments = getJSDocComments(declaration);
            if (!comments) {
                return;
            }
            for (const comment of comments) {
                if (comment) {
                    if (documentationComment.length) {
                        documentationComment.push(lineBreakPart());
                    }
                    documentationComment.push(textPart(comment));
                }
            }
        });
        return documentationComment;
    }

    /**
     * Iterates through 'array' by index and performs the callback on each element of array until the callback
     * returns a truthy value, then returns that value.
     * If no such value is found, the callback is applied to each element of array and undefined is returned.
     */
    function forEachUnique<T, U>(array: T[], callback: (element: T, index: number) => U): U {
        if (array) {
            for (let i = 0, len = array.length; i < len; i++) {
                if (indexOf(array, array[i]) === i) {
                    const result = callback(array[i], i);
                    if (result) {
                        return result;
                    }
                }
            }
        }
        return undefined;
    }

    export function getAllJsDocCompletionEntries(): CompletionEntry[] {
        return jsDocCompletionEntries || (jsDocCompletionEntries = ts.map(jsDocTagNames, tagName => {
            return {
                name: tagName,
                kind: ScriptElementKind.keyword,
                kindModifiers: "",
                sortText: "0",
            };
        }));
    }

    /**
     * Checks if position points to a valid position to add JSDoc comments, and if so,
     * returns the appropriate template. Otherwise returns an empty string.
     * Valid positions are
     *      - outside of comments, statements, and expressions, and
     *      - preceding a:
     *          - function/constructor/method declaration
     *          - class declarations
     *          - variable statements
     *          - namespace declarations
     *
     * Hosts should ideally check that:
     * - The line is all whitespace up to 'position' before performing the insertion.
     * - If the keystroke sequence "/\*\*" induced the call, we also check that the next
     * non-whitespace character is '*', which (approximately) indicates whether we added
     * the second '*' to complete an existing (JSDoc) comment.
     * @param fileName The file in which to perform the check.
     * @param position The (character-indexed) position in the file where the check should
     * be performed.
     */
    export function getDocCommentTemplateAtPosition(newLine: string, sourceFile: SourceFile, position: number): TextInsertion {
        // Check if in a context where we don't want to perform any insertion
        if (isInString(sourceFile, position) || isInComment(sourceFile, position) || hasDocComment(sourceFile, position)) {
            return undefined;
        }

        const tokenAtPos = getTokenAtPosition(sourceFile, position);
        const tokenStart = tokenAtPos.getStart();
        if (!tokenAtPos || tokenStart < position) {
            return undefined;
        }

        // TODO: add support for:
        // - enums/enum members
        // - interfaces
        // - property declarations
        // - potentially property assignments
        let commentOwner: Node;
        findOwner: for (commentOwner = tokenAtPos; commentOwner; commentOwner = commentOwner.parent) {
            switch (commentOwner.kind) {
                case SyntaxKind.FunctionDeclaration:
                case SyntaxKind.MethodDeclaration:
                case SyntaxKind.Constructor:
                case SyntaxKind.ClassDeclaration:
                case SyntaxKind.VariableStatement:
                    break findOwner;
                case SyntaxKind.SourceFile:
                    return undefined;
                case SyntaxKind.ModuleDeclaration:
                    // If in walking up the tree, we hit a a nested namespace declaration,
                    // then we must be somewhere within a dotted namespace name; however we don't
                    // want to give back a JSDoc template for the 'b' or 'c' in 'namespace a.b.c { }'.
                    if (commentOwner.parent.kind === SyntaxKind.ModuleDeclaration) {
                        return undefined;
                    }
                    break findOwner;
            }
        }

        if (!commentOwner || commentOwner.getStart() < position) {
            return undefined;
        }

        const parameters = getParametersForJsDocOwningNode(commentOwner);
        const posLineAndChar = sourceFile.getLineAndCharacterOfPosition(position);
        const lineStart = sourceFile.getLineStarts()[posLineAndChar.line];

        const indentationStr = sourceFile.text.substr(lineStart, posLineAndChar.character);

        let docParams = "";
        for (let i = 0, numParams = parameters.length; i < numParams; i++) {
            const currentName = parameters[i].name;
            const paramName = currentName.kind === SyntaxKind.Identifier ?
                (<Identifier>currentName).text :
                "param" + i;

            docParams += `${indentationStr} * @param ${paramName}${newLine}`;
        }

        // A doc comment consists of the following
        // * The opening comment line
        // * the first line (without a param) for the object's untagged info (this is also where the caret ends up)
        // * the '@param'-tagged lines
        // * TODO: other tags.
        // * the closing comment line
        // * if the caret was directly in front of the object, then we add an extra line and indentation.
        const preamble = "/**" + newLine +
            indentationStr + " * ";
        const result =
            preamble + newLine +
            docParams +
            indentationStr + " */" +
            (tokenStart === position ? newLine + indentationStr : "");

        return { newText: result, caretOffset: preamble.length };
    }

    function getParametersForJsDocOwningNode(commentOwner: Node): ParameterDeclaration[] {
        if (isFunctionLike(commentOwner)) {
            return commentOwner.parameters;
        }

        if (commentOwner.kind === SyntaxKind.VariableStatement) {
            const varStatement = <VariableStatement>commentOwner;
            const varDeclarations = varStatement.declarationList.declarations;

            if (varDeclarations.length === 1 && varDeclarations[0].initializer) {
                return getParametersFromRightHandSideOfAssignment(varDeclarations[0].initializer);
            }
        }

        return emptyArray;
    }

    /**
     * Digs into an an initializer or RHS operand of an assignment operation
     * to get the parameters of an apt signature corresponding to a
     * function expression or a class expression.
     *
     * @param rightHandSide the expression which may contain an appropriate set of parameters
     * @returns the parameters of a signature found on the RHS if one exists; otherwise 'emptyArray'.
     */
    function getParametersFromRightHandSideOfAssignment(rightHandSide: Expression): ParameterDeclaration[] {
        while (rightHandSide.kind === SyntaxKind.ParenthesizedExpression) {
            rightHandSide = (<ParenthesizedExpression>rightHandSide).expression;
        }

        switch (rightHandSide.kind) {
            case SyntaxKind.FunctionExpression:
            case SyntaxKind.ArrowFunction:
                return (<FunctionExpression>rightHandSide).parameters;
            case SyntaxKind.ClassExpression:
                for (const member of (<ClassExpression>rightHandSide).members) {
                    if (member.kind === SyntaxKind.Constructor) {
                        return (<ConstructorDeclaration>member).parameters;
                    }
                }
                break;
        }

        return emptyArray;
    }
}