import { is, Position } from '@preserves/core';
import * as M from './gen/schema';
import { SchemaSyntaxError } from './error';
import { isJsKeyword } from './compiler/jskw';

export * from './gen/schema';

export type Input = M._val;

export function isValidToken(s: string): boolean {
    return /^[a-zA-Z][a-zA-Z_0-9]*$/.test(s);
}

export function isValidJsId(s: string): boolean {
    return /^[$_a-zA-Z][$_a-zA-Z0-9]*$/.test(s) && !isJsKeyword(s);
}

export function jsId(v: string, kf?: () => string): string {
    return jsToken(v.replace('$', '$$').replace('*', '$STAR$'), kf);
}

export function jsToken(s: string, kf?: () => string): string {
    if (isValidJsId(s)) return s;
    if (isValidJsId('$' + s)) return '$' + s;
    if (kf !== void 0) return kf();
    throw new Error(`Internal error: jsToken needs to be completed (${s})`);
}

export const ANDSYM = Symbol.for('&');
export const DOT = Symbol.for('.');
export const DOTDOTDOT = Symbol.for('...');
export const EQUALS = Symbol.for('=');
export const INCLUDE = Symbol.for('include');
export const ORSYM = Symbol.for('/');

export type SchemaEnvEntry = { schemaModulePath: M.ModulePath } & (
    ({
        typescriptModulePath: string | null, // null means it's "this module" in disguise
        schema: M.Schema,
    }) | ({
        typescriptModulePath: string,
        schema: null,
    })
);

export type Environment = Array<SchemaEnvEntry>;

function modsymFor(e: SchemaEnvEntry): string {
    return '_i_' + e.schemaModulePath.map(s => s.description!).join('$');
}

export function lookup<R>(namePos: Position | null,
                          name: M.Ref,
                          env: Environment,
                          kLocal: (p: M.Definition) => R,
                          kOther: (modId: string, modPath: string, p: M.Definition | null) => R): R
{
    for (const e of env) {
        if (is(e.schemaModulePath, name.module) ||
            (e.typescriptModulePath === null && name.module.length === 0))
        {
            if (e.schema === null) {
                // It's an artificial module, not from a schema. Assume the identifier is present.
                return kOther(modsymFor(e), e.typescriptModulePath, null);
            } else {
                const p = e.schema.definitions.get(name.name);
                if (p !== void 0) {
                    if (e.typescriptModulePath === null) {
                        return kLocal(p);
                    } else {
                        return kOther(modsymFor(e), e.typescriptModulePath, p);
                    }
                }
            }
        }
    }

    throw new SchemaSyntaxError(`Undefined reference: ${formatRef(name)}`, namePos);
}

export function formatRef(r: M.Ref): string {
    return [... r.module, r.name].map(s => s.description!).join('.');
}

export function unnamePattern(p: M.NamedPattern): M.Pattern {
    return (p._variant === 'named') ? M.Pattern.SimplePattern(p.value.pattern) : p.value;
}

export function unnameSimplePattern(p: M.NamedSimplePattern): M.SimplePattern {
    return (p._variant === 'named') ? p.value.pattern : p.value;
}

export function promoteNamedSimplePattern(p: M.NamedSimplePattern): M.NamedPattern {
    return (p._variant === 'named') ? p : M.NamedPattern.anonymous(M.Pattern.SimplePattern(p.value));
}

export function nameFor(p: M.NamedSimplePattern | M.NamedPattern) : string | undefined {
    return (p._variant === 'named') ? p.value.name.description! : void 0;
}

export function anonymousSimplePattern(p: M.SimplePattern): M.NamedPattern {
    return M.NamedPattern.anonymous(M.Pattern.SimplePattern(p));
}

export function addNameIfAbsent(p: M.NamedSimplePattern, k: M._val): M.NamedSimplePattern {
    if (p._variant === 'named') {
        return p;
    } else {
        const s = namelike(k);
        if (s !== void 0) {
            return M.NamedSimplePattern.named(M.NamedSimplePattern_({
                name: Symbol.for(s),
                pattern: p.value
            }));
        } else {
            return p;
        }
    }
}

export function namelike(x: Input): string | undefined {
    if (typeof x === 'string') return x;
    if (typeof x === 'symbol') return x.description!;
    if (typeof x === 'number') return '' + x;
    if (typeof x === 'boolean') return '' + x;
    return void 0;
}