import ts = require('typescript');
import { Action } from './mutable-source-code';

/**
 * a transpilation actions API supplied to Visitor at visit time
 */
export interface VisitorContext {
    fileName: string;
    /**
     * was the transpilation declared as failed by any previous visitor
     */
    halted: boolean;
    /**
     * add a text line at given position
     * @param position position in code at which to insert line.
     * @param str line to insert
     */
    insertLine(position: number, str: string): void;

    /**
     * insert text at given position
     * @param position position in code at which to insert line.
     * @param str text to insert
     */
    insert(position: number, str: string): void;

    /**
     * replace a piece of text in the code with a given new text
     * @param start position in code of the first character to replace
     * @param end position in code of the last character to replace. has to be greater or equal to the start param.
     * @param str replacement string to insert instead of original state
     */
    replace(start: number, end: number, str: string): void;
    /**
     * report transpilation diagnostics
     * @param node typescript AST node that relats to this diagnostic
     * @param category severity of the diagnostic to report (could be error, warning or message)
     * @param message txt of the diagnostic
     * @param halt if true, the transpilation is declared as failed
     */
    reportDiag(node: ts.Node, category: ts.DiagnosticCategory, message: string, halt?: boolean): void;

    fastAppend(str: string): void;
    fastRewrite(start: number, str: string): void;

    getLanguageService(): ts.LanguageService;
}

/**
 * single unit of transpilation logic
 */
export interface Visitor {
    /**
     * predicate defining whether this visitor should operate on this node
     * @param node typescript AST node
     */
    filter(node: ts.Node): boolean;
    /**
     * perform visitor logic on given node
     * @param node typescript AST node for which filter(node) returnes true
     * @param context transpilation actions handler for the current visit
     */
    visit(node: ts.Node, context: VisitorContext, traverse: (...visitors: Visitor[]) => void): void;
}