import { Position, TextDocumentContentChangeEvent, TextEditor, TextLine, workspace } from "vscode";
import { Config, ConfigType } from "../../Config";
import Generator from "../../DocGen/CGen";
import { IDocGen } from "../../DocGen/DocGen";
import ICodeParser from "../CodeParser";
import { Argument } from "./Argument";
import { ParseTree } from "./ParseTree";
import { Token, TokenType } from "./Token";

/**
 *
 * Parses C code for methods and signatures
 *
 * @export
 * @class CParser
 * @implements {ICodeParser}
 */
export default class CParser implements ICodeParser {
    protected activeEditor: TextEditor;
    protected activeSelection: Position;

    private typeKeywords: string[];
    private stripKeywords: string[];
    private keywords: string[];
    private lexerVocabulary;

    constructor() {
        this.typeKeywords = [
            "const",
            "struct",
        ];

        this.stripKeywords = [
            "static",
            "inline",
            "friend",
            "virtual",
            "extern",
            "explicit",
            "class",
            "override",
        ];

        // Non type keywords will be stripped from the final return type.
        this.keywords = this.typeKeywords.concat(this.stripKeywords);

        this.lexerVocabulary = {
            ArraySubscript: (x: string): string => (x.match("^\\[[^\\[]*?\\]") || [])[0],
            Arrow: (x: string): string => (x.match("^->") || [])[0],
            Assignment: (x: string): string => (x.match("^=") || [])[0],
            Attribute: (x: string): string => (x.match("^\\[\\[[^\\[]*?\\]\\]") || [])[0],
            CloseParenthesis: (x: string): string => (x.match("^\\)") || [])[0],
            Comma: (x: string): string => (x.match("^,") || [])[0],
            CommentBlock: (x: string): string => {
                if (x.startsWith("/*") === false) {
                    return undefined;
                }

                let closeOffset: number = x.indexOf("*/");
                closeOffset = closeOffset === -1 ? x.length : closeOffset + 2;
                return x.slice(0, closeOffset);
            },
            CommentLine: (x: string): string => {
                if (x.startsWith("//") === false) {
                    return undefined;
                }

                let closeOffset: number = x.indexOf("\n");
                closeOffset = closeOffset === -1 ? x.length : closeOffset + 1;
                return x.slice(0, closeOffset);
            },
            CurlyBlock: (x: string): string => {
                if (x.startsWith("{") === false) {
                    return undefined;
                }
                const startEndOffset: number[] = this.GetSubExprStartEnd(x, 0, "{", "}");
                return startEndOffset[1] === 0 ? undefined : x.slice(0, startEndOffset[1]);
            },
            Ellipsis: (x: string): string => (x.match("^\\.\\.\\.") || [])[0],
            OpenParenthesis: (x: string): string => (x.match("^\\(") || [])[0],
            Pointer: (x: string): string => (x.match("^\\*") || [])[0],
            Reference: (x: string): string => (x.match("^&") || [])[0],
            Symbol: (x: string): string => {
                // Handle access specifiers since they aren't really symbols.
                if (x.startsWith("public:") || x.startsWith("protected:") || x.startsWith("private:")) {
                    return undefined;
                }
                // Handle operator and decltype special cases.
                if (x.startsWith("operator") === true) {
                    const startBrace: number = x.indexOf("(");
                    return startBrace === -1 ? undefined : x.slice(0, startBrace);
                } else if (x.startsWith("decltype") === true) {
                    const startEndOffset: number[] = this.GetSubExprStartEnd(x, 0, "(", ")");
                    return startEndOffset[1] === 0 ? undefined : x.slice(0, startEndOffset[1]);
                }

                const reMatch: string = (x.match("^[a-z|A-Z|:|_|~|\\d]+") || [])[0];
                if (reMatch === undefined) {
                    return undefined;
                }

                // Check if symbol includes a template for instance Matrix<T, M, N> and include it if so.
                if (x.slice(reMatch.length, x.length).trim().startsWith("<") === false) {
                    return reMatch;
                }

                const offsets: number[] = this.GetSubExprStartEnd(x, reMatch.length, "<", ">");
                return offsets[1] === 0 ? undefined : x.slice(0, offsets[1]);
            },
        };
    }

    /**
     * @inheritdoc
     */
    public Parse(activeEdit: TextEditor): IDocGen {
        this.activeEditor = activeEdit;
        this.activeSelection = this.activeEditor.selection.active;

        let line: string = "";
        try {
            line = this.getLogicalLine();
        } catch (err) {
            // console.dir(err);
        }

        // template parsing is simpler by using heuristics rather then tokenizing first.
        const template: string = this.GetTemplate(line);
        const templateArgs: string[] = this.GetArgsFromTemplate(template);

        line = line.slice(template.length, line.length + 1).trim();

        let retAndArgs: string[][] = [[], []];
        try {
            retAndArgs = this.GetReturnAndArgs(line);
        } catch (err) {
            // console.dir(err);
        }

        const retVals = retAndArgs[0];
        const args = retAndArgs[1];

        const cppGenerator: IDocGen = new Generator(
            this.activeEditor,
            this.activeSelection,
            args,
            templateArgs,
            retVals,
        );

        return cppGenerator;
    }

    /***************************************************************************
                                    Implementation
     ***************************************************************************/
    private getLogicalLine(): string {
        let logicalLine: string = "";

        let nextLine: Position = new Position(this.activeSelection.line + 1, this.activeSelection.character);

        let nextLineTxt: string = this.activeEditor.document.lineAt(nextLine.line).text.trim();

        // VSCode may enter a * on itself, we don"t want that in our method
        if (nextLineTxt === "*") {
            nextLineTxt = "";
        }

        let currentNest: number = 0;
        logicalLine = nextLineTxt;

        // Get method end line
        let linesToGet: number = 20;
        while (linesToGet-- > 0) { // Check for end of expression.
            nextLine = new Position(nextLine.line + 1, nextLine.character);
            nextLineTxt = this.activeEditor.document.lineAt(nextLine.line).text.trim();

            // Check if method has finished if curly brace is opened while
            // nesting is occuring.
            for (let i: number = 0; i < nextLineTxt.length; i++) {
                if (nextLineTxt[i] === "(") {
                    currentNest++;
                } else if (nextLineTxt[i] === ")") {
                    currentNest--;
                } else if (nextLineTxt[i] === "{" && currentNest === 0) {
                    logicalLine += "\n" + nextLineTxt.slice(0, i);
                    return logicalLine.replace(/^\s+|\s+$/g, "");
                } else if (nextLineTxt[i] === ";" && currentNest === 0) {
                    logicalLine += "\n" + nextLineTxt.slice(0, i);
                    return logicalLine.replace(/^\s+|\s+$/g, "");
                }
            }

            logicalLine += "\n" + nextLineTxt;
        }

        throw new Error("More then 20 lines were gotten from editor and no end of expression was found.");
    }

    private Tokenize(expression: string): Token[] {
        const tokens: Token[] = [];
        expression = expression.replace(/^\s+|\s+$/g, "");

        while (expression.length !== 0) {
            const matches: Token[] = Object.keys(this.lexerVocabulary)
                .map((k): Token => new Token(TokenType[k], this.lexerVocabulary[k](expression)))
                .filter((t) => t.Value !== undefined);

            if (matches.length === 0) {
                throw new Error("Next token couldn\'t be determined: " + expression);
            } else if (matches.length > 1) {
                throw new Error("Multiple matches for next token: " + expression);
            }

            tokens.push(matches[0]);
            expression = expression.slice(matches[0].Value.length, expression.length).replace(/^\s+|\s+$/g, "");
        }

        return tokens;
    }

    private GetReturnAndArgs(line: string): string[][] {
        const retVals: string[] = [];
        let args: string[] = [];

        // Tokenize rest of expression and remove comment tokens;
        const tokens: Token[] = this.Tokenize(line)
            .filter((t) => t.Type !== TokenType.CommentBlock)
            .filter((t) => t.Type !== TokenType.CommentLine);

        // Create hierarchical tree based on the parenthesis.
        const tree: ParseTree = ParseTree.CreateTree(tokens).Compact();

        // return argument.
        const returnArg = this.GetArgument(tree);

        // Check if return type is a pointer
        const ptrReturnIndex = returnArg.Type.nodes
            .findIndex((n) => n instanceof Token && n.Type === TokenType.Pointer);

        // Special case for void functions.
        const voidReturnIndex = returnArg.Type.nodes
            .findIndex((n) => n instanceof Token && n.Type === TokenType.Symbol && n.Value === "void");

        // Special case for bool return type.
        const boolReturnIndex: number = returnArg.Type.nodes
            .findIndex((n) => n instanceof Token && n.Type === TokenType.Symbol && n.Value === "bool");

        if (boolReturnIndex !== -1) {
            retVals.push("true");
            retVals.push("false");
            if (ptrReturnIndex !== -1) {
                retVals.push("null");
            }
        } else if (voidReturnIndex !== -1 && ptrReturnIndex !== -1) {
            retVals.push(returnArg.Type.Yield());
        } else if (voidReturnIndex === -1 && returnArg.Type.nodes.length > 0) {
            retVals.push(returnArg.Type.Yield());
        }

        // Get arguments list as a parsetree and create arguments from them.
        args = this.GetArgumentList(tree)
            .map((a) => this.GetArgument(a))
            .map((a) => a.Name === undefined ? "" : a.Name);

        return [retVals, args];
    }

    private RemoveUnusedTokens(tree: ParseTree): ParseTree {
        tree = tree.Copy();

        // First slice of everything after assignment since that will not be used.
        const assignmentIndex = tree.nodes.findIndex((n) => n instanceof Token && n.Type === TokenType.Assignment);
        if (assignmentIndex !== -1) {
            tree.nodes = tree.nodes.slice(0, assignmentIndex);
        }

        // Check if there is an initializer list and slice of everything after it.
        const initializerList = tree.nodes
            .findIndex((n) => n instanceof Token && n.Type === TokenType.Symbol && n.Value === ":");
        if (initializerList !== -1) {
            tree.nodes = tree.nodes.slice(0, initializerList);
        }

        return tree;
    }

    private GetArgumentList(tree: ParseTree): ParseTree[] {
        const args: ParseTree[] = [];

        tree = this.RemoveUnusedTokens(tree);

        let cursor: ParseTree = tree;
        while (this.IsFuncPtr(cursor.nodes) === true) {
            cursor = cursor.nodes.find((n) => n instanceof ParseTree) as ParseTree;
        }

        const argTree: ParseTree = cursor.nodes.find((n) => n instanceof ParseTree) as ParseTree;
        if (argTree === undefined) {
            throw new Error("Function arguments not found.");
        }

        // Split the argument tree on commas
        let arg: ParseTree = new ParseTree();
        for (const node of argTree.nodes) {
            if (node instanceof Token && node.Type === TokenType.Comma) {
                args.push(arg);
                arg = new ParseTree();
            } else {
                arg.nodes.push(node);
            }
        }

        if (arg.nodes.length > 0) {
            args.push(arg);
        }

        return args;
    }

    private IsFuncPtr(nodes: Array<Token | ParseTree>) {
        return nodes.filter((n) => n instanceof ParseTree).length === 2;
    }

    private StripNonTypeNodes(tree: ParseTree) {
        tree.nodes = tree.nodes
            // All strippable keywords.
            .filter((n) => {
                return !(n instanceof Token
                    && n.Type === TokenType.Symbol
                    && this.stripKeywords.find((k) => k === n.Value) !== undefined);
            })
            // Attributes aren't part of the type.
            .filter((n) => !(n instanceof Token && n.Type === TokenType.Attribute));
    }

    private GetArgumentFromTrailingReturn(tree: ParseTree, startTrailingReturn: number): Argument {
        const argument: Argument = new Argument();

        // Find index of auto prior to the first parseTree.
        // If auto is not found something is going wrong since trailing return
        // requires auto.
        let autoIndex: number = -1;
        for (let i: number = 0; i < tree.nodes.length; i++) {
            const node = tree.nodes[i];
            if (node instanceof ParseTree) {
                break;
            }
            if (node.Type === TokenType.Symbol && node.Value === "auto") {
                autoIndex = i;
                break;
            }
        }

        if (autoIndex === -1) {
            throw new Error("Function declaration has trailing return but type is not auto.");
        }

        // Get symbol between auto and parseTree which is the argument name. It also may not be a keyword.
        for (let i: number = autoIndex + 1; i < tree.nodes.length; i++) {
            const node = tree.nodes[i];
            if (node instanceof ParseTree) {
                break;
            }
            if (node.Type === TokenType.Symbol && this.keywords.find((k) => k === node.Value) === undefined) {
                argument.Name = node.Value;
                break;
            }
        }

        argument.Type.nodes = tree.nodes.slice(startTrailingReturn + 1, tree.nodes.length);
        this.StripNonTypeNodes(argument.Type);

        return argument;
    }

    private GetArgumentFromFuncPtr(tree: ParseTree): Argument {
        const argument: Argument = new Argument();

        argument.Type = tree;

        let cursor: ParseTree = tree;

        while (this.IsFuncPtr(cursor.nodes) === true) {
            cursor = cursor.nodes.find((n) => n instanceof ParseTree) as ParseTree;
        }

        // Remove parseTree. This can be if it is a function declaration.
        const argumentsIndex = cursor.nodes.findIndex((n) => n instanceof ParseTree);
        if (argumentsIndex !== -1) {
            cursor.nodes.splice(argumentsIndex, 1);
        }

        // Find first symbol that is the argument name.
        // Remove it from the tree and set the name to the argument name
        for (let i: number = 0; i < cursor.nodes.length; i++) {
            const node = cursor.nodes[i];
            if (node instanceof ParseTree) {
                continue;
            }

            if (node.Type === TokenType.Symbol && this.keywords.find((k) => k === node.Value) === undefined) {
                argument.Name = node.Value;
                cursor.nodes.splice(i, 1);
            }
        }

        this.StripNonTypeNodes(argument.Type);
        return argument;
    }

    private GetDefaultArgument(tree: ParseTree): Argument {
        const argument: Argument = new Argument();

        for (let i = tree.nodes.length - 1; i >= 0; i--) {
            const node = tree.nodes[i];
            if (node instanceof Token && node.Type === TokenType.Symbol) {
                argument.Name = node.Value;
                tree.nodes.splice(i, 1);
                break;
            }
        }

        if (tree.nodes.length > 0) {
            argument.Type.nodes = tree.nodes.filter((x) => x instanceof Token);
        }

        this.StripNonTypeNodes(argument.Type);
        return argument;
    }

    private GetArgument(tree: ParseTree): Argument {
        // Copy tree structure leave original untouched.
        const copy = this.RemoveUnusedTokens(tree);

        // Special case with only ellipsis. C style variadic arguments
        if (copy.nodes.length === 1) {
            const node = copy.nodes[0];
            if (node instanceof Token && node.Type === TokenType.Ellipsis) {
                const argument: Argument = new Argument();
                argument.Name = node.Value;
                return argument;
            }
        }

        // Check if it is has a trailing return.
        const startTrailingReturn: number = copy.nodes
            .findIndex((t) => t instanceof Token ? t.Type === TokenType.Arrow : false);

        // Special case trailing return.
        if (startTrailingReturn !== -1) {
            return this.GetArgumentFromTrailingReturn(copy, startTrailingReturn);
        }

        // Handle function pointers
        if (this.IsFuncPtr(copy.nodes) === true) {
            return this.GetArgumentFromFuncPtr(copy);
        }

        return this.GetDefaultArgument(copy);
    }

    private GetSubExprStartEnd(expression: string, startSearch: number, openExpr: string, closeExpr: string): number[] {
        let openExprOffset: number = -1;
        let nestedCount: number = 0;
        for (let i: number = startSearch; i < expression.length; i++) {
            if (expression[i] === openExpr && openExprOffset === -1) {
                openExprOffset = i;
            }

            if (expression[i] === openExpr) {
                nestedCount++;
            } else if (expression[i] === closeExpr && nestedCount > 0) {
                nestedCount--;
            }

            if (expression[i] === closeExpr && nestedCount === 0 && openExprOffset !== -1) {
                return [openExprOffset, i + 1];
            }
        }

        return [0, 0];
    }

    private GetTemplate(expression: string): string {
        if (expression.startsWith("template") === false) {
            return "";
        }

        let startTemplateOffset: number = -1;
        for (let i: number = "template".length; i < expression.length; i++) {
            if (expression[i] === "<") {
                startTemplateOffset = i;
                break;
            } else if (expression[i] !== " ") {
                return "";
            }
        }

        if (startTemplateOffset === -1) {
            return "";
        }

        const [start, end] = this.GetSubExprStartEnd(expression, startTemplateOffset, "<", ">");
        return expression.slice(0, end);
    }

    private GetArgsFromTemplate(template: string): string[] {
        const args: string[] = [];
        if (template === "") {
            return args;
        }

        // Remove <> and add a comma to the end to remove edge case.
        template = template.slice(template.indexOf("<") + 1, template.lastIndexOf(">")).replace(/^\s+|\s+$/g, "") + ",";

        const nestedCounts: { [key: string]: number; } = {
            "(": 0,
            "<": 0,
            "{": 0,
        };

        let lastSeparator: number = 0;
        for (let i: number = 0; i < template.length; i++) {
            const notInSubExpr: boolean = nestedCounts["<"] === 0
                && nestedCounts["("] === 0
                && nestedCounts["{"] === 0;

            if (notInSubExpr === true && template[i] === ",") {
                args.push(template.slice(lastSeparator + 1, i).replace(/^\s+|\s+$/g, ""));
            } else if (notInSubExpr === true && (template[i] === " " || template[i] === ".")) {
                lastSeparator = i;
            }

            if (template[i] === "(") {
                nestedCounts["("]++;
            } else if (template[i] === ")" && nestedCounts["("] > 0) {
                nestedCounts["("]--;
            } else if (template[i] === "<") {
                nestedCounts["<"]++;
            } else if (template[i] === ">" && nestedCounts["<"] > 0) {
                nestedCounts["<"]--;
            } else if (template[i] === "{") {
                nestedCounts["{"]++;
            } else if (template[i] === "}" && nestedCounts["{"] > 0) {
                nestedCounts["{"]--;
            }
        }

        return args;
    }
}