import Fiber = require('../fibers');
import RunContext = require('./runContext');
export = FiberManager;


/** Helpers for Fiber management. */
module FiberManager {

    /** Returns true if the current execution context is within a fiber. */
    export function isExecutingInFiber() {
        return !!Fiber.current;
    }

    /** Creates and returns a new fiber in which an arbitrary function may be executed. */
    export function create(): FiberEx {
        return Fiber(runInFiber);
    }

    export interface FiberEx extends Fiber {

        /**
         * Executes the wrapped function specified in the RunContext instance. The final
         * return/throw value of the wrapped function is used to notify the promise resolver
         * and/or callback specified in the RunContext.
         */
        run(runCtx: RunContext): void;
    }
}


/**
 * The runInFiber() function provides the prolog/epilog wrapper code for running a function inside
 * a fiber. The runInFiber() function accepts a RunContext instance, and calls the wrapped function
 * specified there. The final return/throw value of the wrapped function is used to notify the 
 * promise resolver and/or callback specified in the RunContext. This function must take all its
 * information in a single argument because it is called via Fiber#run(), which accepts one argument.
 * NB: Since try/catch/finally prevents V8 optimisations, the function is split into several parts.
 */
function runInFiber(runCtx: RunContext) {
    try         { tryBlock(runCtx);        }
    catch (err) { catchBlock(runCtx, err); }
    finally     { finallyBlock(runCtx);    }
}
function tryBlock(runCtx: RunContext) {
    
    // Maintain an accurate count of currently active fibers, for pool management.
    adjustFiberCount(+1);

    // Call the wrapped function. It may be suspended several times (at await and/or yield calls).
    var result = runCtx.wrapped.apply(runCtx.thisArg, runCtx.argsAsArray);

    // The wrapped function returned normally. Notify any waiters.
    if (runCtx.callback) runCtx.callback(null, result);
    if (runCtx.resolver) runCtx.resolver.resolve(result);
}
function catchBlock(runCtx: RunContext, err) {

    // The wrapped function threw an exception. Notify any waiters.
    if (runCtx.callback) runCtx.callback(err);
    if (runCtx.resolver) runCtx.resolver.reject(err);
}
function finallyBlock(runCtx: RunContext) {

    // Maintain an accurate count of currently active fibers, for pool management.
    adjustFiberCount(-1);

    // Execute the done() callback, if provided.
    if (runCtx.done) runCtx.done();
}




/**
 * The following functionality prevents memory leaks in node-fibers by actively managing Fiber.poolSize.
 * For more information, see https://github.com/laverdet/node-fibers/issues/169.
 */
function adjustFiberCount(delta: number) {
    activeFiberCount += delta;
    if (activeFiberCount >= fiberPoolSize) {
        fiberPoolSize += 100;
        Fiber.poolSize = fiberPoolSize;
    }
}
var fiberPoolSize = Fiber.poolSize;
var activeFiberCount = 0;