import { Component, ElementRef, Renderer2, ViewChild } from '@angular/core';
import { FormsModule } from '@angular/forms'

// type descriptions

// a formatDescriptor contains information for the renderer to apply formatting styles to a node
interface formatDescriptor {
    className: string;
};

// a textNode is an element produced by the parser to link text to applied format specifiers. The renderer will
// apply each style to the text in the node according to the styles registry.
interface textNode {
    type: string;
    text: string;
    styles: string[]
}

// a blockNode is an element produced by the parser to structure nodes by blocks. blocks contain child nodes, either
// other blocks or text nodes at the bottom. A block node's html element type is described by kind: p, h1, h2, div, etc
// Maybe we blocks can also have styles, and then we can join textNode and blockNode into a single type.
interface blockNode {
    type: string;
    kind: string;
    children: (blockNode | textNode)[]
}

// styles registry: this maps format specifiers to css classes
// might move this to its own file
const styles: Record<string, formatDescriptor> = {
    B: {
        className: "format-bold"
    },
    I: {
        className: "format-italic"
    },
    U: {
        className: "format-underline"
    },
    S: {
        className: "format-strikethrough"
    } // TODO: some css style elements cannot simply be overlapped. strikethrough and underline both use the
    // "text decoration" tag so simply applying both will overwrite one of the styles. some extra logic will have to
    // be put in place to add a combined "format-strikethrough-formatunderline" style in which the text decoration
    // contains both.
}; // i.e. %B{...} will apply "format-bold"

// blocks registry: this maps format specifiers to html block types
// if moved to another file, should stick next to the styles registry
const blocks: Record<string, formatDescriptor> = {
    H1: {
        className: "h1"
    },
    H2: {
        className: "h2"
    },
    H3: {
        className: "h3"
    },
    P: {
        className: "p"
    },
    D: {
        className: "div"
    }
    // TODO: lists
}; // i.e. #H1{...} will create a h1 element

// angular component class
@Component({
    selector: 'app-markleft',
    imports: [FormsModule],
    templateUrl: './markleft.html',
    styleUrl: './markleft.scss',
})
export class Markleft {

    @ViewChild('markup_container', { static: true }) container!: ElementRef;

    constructor(private renderer: Renderer2) {
        
    }

    ngOnInit() { // DOM manipulation can't occur in constructor
        this.refresh();
    }

    // live update on each text input.
    onTextUpdate(event: Event) {
        this.refresh();
    }

    // default text
    liveText: string = `
        #H1{Hello World!}
        #H2{hi mom !!}
        #P{
            This is some %B{PhAML} (%I{%B{Ph}ishly %B{A}mazing %B{M}arkup %B{L}anguage}) text. This is %I{italic} and this is %B{bold}. Some might %I{even be %B{both}}.
        }
        This should be plain and unstylized.
    `;

    // parses a single string into an array of nodes
    // like noted at parseStyle, maybe can return a single node which itself contains the array of children.
    parsePlaintext(input: string): (textNode | blockNode)[] {

        let index: number = 0; // position in the input string
        let nodes: (textNode | blockNode)[] = [];

        // TODO: I might restructure the node parsing so that it starts with a generic top level node and can process all children under that node
        function parseStyle(parentNode: blockNode | null = null, parentStyles: string[] | null = null) {

            // step onto format specifier code
            index++;
            let codeIndexStart: number = index;
            while(input[index] != "{") { // continue stepping forward until we hit a { character
                index++;
                if(index >= input.length) break;
            } 
            // the resulting substring between the style character and the { is our style code
            const code: string = input.substring(codeIndexStart, index); 
            if(!(code in styles)) {
                console.log("Style identifier is not recognized: ", code);
            }

            let styleList: string[] = [];
            if(parentStyles) {
                styleList = [...parentStyles, code] // append style code to styles list of this node
            } else {
                styleList= [code];
            }
            
            let text: string = "";
            while(true) { // assemble text
                index++;
                if(input[index] === "%") { // encountered another style specifier
                    // commit the current node
                    addTextNode(text, styleList, parentNode);
                    text = ""; // clear the already commited text
                    // and then move to the next
                    parseStyle(parentNode ? parentNode : null, styleList); // recursion

                } else if(input[index] == "}") { // this node has closed
                    addTextNode(text, styleList, parentNode);
                    break;
                } else { // regular text
                    text += input[index]; // append character to the text string
                }
                if(index >= input.length) {
                    break;
                }
            }
        }

        function parseStructure(parentNode: blockNode | null = null) {

            // step onto format specifier code
            index++;
            let codeIndexStart: number = index;
            while(input[index] != "{") { // continue stepping forward until we hit a { character
                index++;
                if(index >= input.length) break;
            } 
            // the resulting substring between the style character and the { is our style code
            const code: string = input.substring(codeIndexStart, index); 
            if(!(code in blocks)) {
                console.log("Code is not recognized: ", code);
            }
            
            // create the node
            const node: blockNode = {
                type: "block",
                kind: code,
                children: [] // this blockNode will get passed to children so they can be added to the parent
            };

            let text: string = "";
            while(true) { // assemble text
                index++;
                if(input[index] === "%" || input[index] === "#") { // encountered another format specifier
                    addTextNode(text, null, node);
                    text = ""; // clear the already commited text
                    // and then move to the next
                    if(input[index] === "%") {
                        parseStyle(node, null); // pass in the current node as the future node's parent
                    } else if(input[index] === "#") {
                        parseStructure(node);
                    }
                } else if(input[index] == "}") { // this node has closed
                    index++;
                    // add its text
                    addTextNode(text, null, node);
                    // push node to children list
                    if(parentNode) {
                        parentNode.children.push(node);
                    } else {
                        nodes.push(node);
                    }

                    break;
                } else { // regular text
                    text += input[index];
                }
                if(index >= input.length) {
                    break;
                }
            }
        }

        function addTextNode(text: string, styles: string[] | null = null, parentNode: blockNode | null = null) {
            if(text.length === 0) return;
            const textNode: textNode = {
                type: "text",
                text: text,
                styles: styles ? styles : []
            }
            if(parentNode) {
                parentNode.children.push(textNode);
            } else {
                nodes.push(textNode);
            }
        }

        function parse(endChar: string | null = null) {
            let currentText: string = "";
            while(index < input.length) {
                if(endChar && (input[index] === endChar)) {
                    index++;
                    break;
                }
                if(input[index] === "%") { // encountered a style specifier
                    addTextNode(currentText);
                    parseStyle();
                    currentText = "";
                } else if(input[index] === "#") { // encountered a structure specifier
                    addTextNode(currentText);
                    parseStructure();
                    currentText = "";
                } else if(input[index] === "@") { // encountered an attribute specifier
                    // nodes.push(parseAttribute()); // TODO: implement
                } else {
                    // regular character
                    currentText += input[index];
                    index++;
                }
            }
            addTextNode(currentText);
        }

        parse();

        return nodes;
    }

    renderNode(node: textNode | blockNode, parentContainer: any = null): void {

        if("styles" in node) { // this node is a textNode

            const span = this.renderer.createElement("span"); // create container

            node.styles.forEach((style: string) => {
                this.renderer.addClass(span, styles[style].className);
            });

            const text = this.renderer.createText(node.text); // create text

            this.renderer.appendChild(span, text); // add text to container
            if(parentContainer) { // this container is a child
                this.renderer.appendChild(parentContainer, span);
            } else { // add to the top-level DOM
                this.renderer.appendChild(this.container.nativeElement, span);
            }

        } else if("kind" in node) { // this is a blockNode

            let container: any;
            container = this.renderer.createElement(blocks[node.kind].className);

            node.children.forEach((child: textNode | blockNode) => {
                if("styles" in child) { // this is a textNode
                    if(child.styles.length === 0) {
                        // just add text
                        const text = this.renderer.createText(child.text); // create text
                        this.renderer.appendChild(container, text); // add text to container
                    } else {
                        // render styles
                        this.renderNode(child, container); // recursion
                    }
                } else if("kind" in child) { // this is a block node
                    this.renderNode(child, container); // recursion
                }
            });

            // add container to DOM
            if(parentContainer) { // this container is a child
                this.renderer.appendChild(parentContainer, container);
            } else { // add to the top-level DOM
                this.renderer.appendChild(this.container.nativeElement, container);
            }
        }

        return;
    }

    refresh() {

        // clear children
        const parent = this.container.nativeElement;
        while (parent.firstChild) {
            this.renderer.removeChild(parent, parent.firstChild);
        }

        // parse text
        const nodes: (textNode | blockNode)[] = this.parsePlaintext(this.liveText);

        // render nodes
        nodes.forEach((node) => {
            this.renderNode(node);
        });

    }
}