import { Palette } from "./highlighter/palette";
import { Node, Position } from "./highlighter/node";
import { State } from "./highlighter/state";
import { Token, Type } from "./tokenizer/token";
import { TODO, VERIFY, VERIFY_NOT_REACHED } from "../util/assertions.js";

export class Highlighter {
    private state: State = State.Undefined;
    private returnState!: State;

    private currentToken!: Token;
    private currentNode!: Node;

    public nodes: Array<Node> = new Array<Node>();
    private pointer: number = 0;

    public finished: boolean = false;

    public constructor(private tokens: Array<Token>) {
    }

    public spin(): void {
        switch (this.state) {
        case State.Undefined: {
            switch (this.consumeNextTokenType()) {
                case Type.Character: this.reconsumeIn(State.BeforePlain); break;
                case Type.StartTag: this.reconsumeIn(State.StartTag); break;
                case Type.EndTag: this.reconsumeIn(State.EndTag); break;
                case Type.DOCTYPE: this.reconsumeIn(State.DOCTYPE); break;
                case Type.Comment: this.reconsumeIn(State.Comment); break;
                case Type.EndOfFile: this.finished = true; break;
                default: TODO(`Unimplemented token type '${this.currentToken.type}'`);
            }

            break;
        }
        case State.BeforePlain: {
            switch (this.consumeNextTokenType()) {
                case Type.Character:
                    this.createNode({ position: { line: 0, character: 0 }, color: Palette.Plain, content: '' });
                    this.reconsumeIn(State.Plain);
                    break;
                default: VERIFY_NOT_REACHED(this.currentToken.type);
            }

            break;
        }
        case State.Plain: {
            switch (this.consumeNextTokenType()) {
                case Type.Character: this.currentNode.content += this.currentTokenOfType(Type.Character).data; break;
                default:
                    this.emitNode(this.currentNode);
                    this.reconsumeIn(State.Undefined);
            }

            break;
        }
        case State.StartTag: {
            switch (this.consumeNextTokenOfType(Type.StartTag).name) {
                case 'script': this.returnState = State.BeforeScript; break;
                default: this.returnState = State.Undefined; break;
            }

            this.emitNode({ position: { line: 0, character: 0 }, color: Palette.Punctuator, content: `<` });
            this.emitNode({ position: { line: 0, character: 0 }, color: Palette.Tag, content: this.currentTokenOfType(Type.StartTag).name });

            if (this.currentTokenOfType(Type.StartTag).attributes.nonEmpty()) {
                this.emitSpace({ line: 0, character: 0 });
                this.reconsumeIn(State.Attributes);
            }

            this.reconsumeIn(State.AfterAttributes);

            this.state = this.returnState;

            break;
        }
        case State.EndTag: {
            this.emitNode({ position: { line: 0, character: 0 }, color: Palette.Punctuator, content: '</' });
            this.emitNode({ position: { line: 0, character: 0 }, color: Palette.Tag, content: this.consumeNextTokenOfType(Type.EndTag).name });

            this.reconsumeIn(State.AfterAttributes);

            this.state = State.Undefined;

            break;
        }
        case State.Attributes: {
            const attributes = this.consumeNextTokenOfEitherType(Type.StartTag, Type.EndTag).attributes.list;

            for (let i = 0; i < attributes.length; i++) {
                const attribute = attributes[i];

                this.emitNode({ position: { line: 0, character: 0 }, color: Palette.Attribute, content: attribute.name });
                this.emitNode({ position: { line: 0, character: 0 }, color: Palette.Punctuator, content: '=' });
                this.emitNode({ position: { line: 0, character: 0 }, color: Palette.String, content: `"${attribute.value}"` });

                if (i !== attributes.length - 1) this.emitSpace({ line: 0, character: 0 });
            }

            break;
        }
        case State.AfterAttributes: {
            switch (this.consumeNextTokenType()) {
                case Type.StartTag:
                    if (this.currentTokenOfType(Type.StartTag).selfClosing === undefined) {
                        this.emitNode({ position: { line: 0, character: 0 }, color: Palette.Punctuator, content: '>' });
                    } else {
                        this.emitSpace({ line: 0, character: 0 });
                        this.emitNode({ position: { line: 0, character: 0 }, color: Palette.Punctuator, content: '/>' });
                    }
                    break;
                case Type.EndTag:
                    this.emitNode({ position: { line: 0, character: 0 }, color: Palette.Punctuator, content: '>' });
                    break;
                default: VERIFY_NOT_REACHED(this.currentToken.type);
            }

            break;
        }
        case State.BeforeScript: {
            switch (this.consumeNextTokenType()) {
                case Type.Character:
                    this.createNode({ position: { line: 0, character: 0 }, color: Palette.String, content: '' });
                    this.reconsumeIn(State.Script);
                    break;
                case Type.EndTag: this.reconsumeIn(State.EndTag); break;
                default: VERIFY_NOT_REACHED(this.currentToken.type);
            }

            break;
        }
        case State.Script: {
            switch (this.consumeNextTokenType()) {
                case Type.Character: this.currentNode.content += this.currentTokenOfType(Type.Character).data; break;
                default:
                    this.emitNode(this.currentNode);
                    this.reconsumeIn(State.Undefined);
            }

            break;
        }
        case State.DOCTYPE: {
            const doctype = this.consumeNextTokenOfType(Type.DOCTYPE);

            this.emitNode({ position: { line: 0, character: 0 }, color: Palette.Punctuator, content: '<!' });
            this.emitNode({ position: { line: 0, character: 0 }, color: Palette.Tag, content: 'DOCTYPE' });
            this.emitSpace({ line: 0, character: 0 });

            // FIXME: Implement more doctype values
            if (doctype.name !== undefined) this.emitNode({ position: { line: 0, character: 0 }, color: Palette.Attribute, content: doctype.name })

            this.emitNode({ position: { line: 0, character: 0 }, color: Palette.Punctuator, content: '>' });

            this.state = State.Undefined;

            break;
        }
        case State.Comment:
            this.emitNode({ position: { line: 0, character: 0 }, color: Palette.Comment, content: `<!--${this.consumeNextTokenOfType(Type.Comment).data}-->` });

            this.state = State.Undefined;
            break;
        default: TODO(`Unimplemented state '${this.state}'`);
        }
    }

    private emitNode(node: Node): void {
        this.nodes.push(node);
    }

    private emitSpace(position: Position): void {
        this.nodes.push({ position, color: Palette.Plain, content: ' ' });
    }

    private createNode(node: Node): Node {
        return this.currentNode = node;
    }

    private consumeNextTokenOfType<T extends Type>(type: T): Token & { type: T } {
        this.currentToken = this.tokens[this.pointer];

        VERIFY(this.currentToken.type === type, `Expected '${type}', got '${this.currentToken.type}' instead`);

        this.pointer++;

        return this.currentToken as Token & { type: T };
    }

    private consumeNextTokenOfEitherType<T extends Type, U extends Type>(a: T, b: U): Token & { type: T | U } {
        this.currentToken = this.tokens[this.pointer];

        VERIFY(this.currentToken.type === a || this.currentToken.type === b, `Expected '${a}' or '${b}', got '${this.currentToken.type}' instead`);

        this.pointer++;

        return this.currentToken as Token & { type: T };
    }

    private consumeNextTokenType(): Type {
        this.currentToken = this.tokens[this.pointer];
        this.pointer++;

        return this.currentToken?.type;
    }

    private consumeNextToken(): Token {
        this.currentToken = this.tokens[this.pointer];
        this.pointer++;

        return this.currentToken; 
    }

    private currentTokenOfType<T extends Type>(type: T): Token & { type: T } {
        VERIFY(this.currentToken.type === type, `Expected '${type}', got '${this.currentToken.type}' instead`);

        return this.currentToken as Token & { type: T };
    }

    private currentTokenOfEitherType<T extends Type, U extends Type>(a: T, b: U): Token & { type: T | U } {
        VERIFY(this.currentToken.type === a || this.currentToken.type === b, `Expected '${a}' or '${b}', got '${this.currentToken.type}' instead`);

        return this.currentToken as Token & { type: T };
    }

    private reconsumeIn(state: State): void {
        this.pointer--;
        this.state = state;
        this.spin();
    }
}