/* fabric.c -- nodes, wiring, and time passing for all of them.  See fabric.h.
 *
 * Nothing here uses the C library: the bare-metal kernel links this file.
 */
#include "v4/fabric.h"

static void clear_place(v4_place *p)
{
    unsigned k;
    p->node = 0;
    p->asleep = 0;
    for (k = 0; k < V4_PORTS; k++) { p->wire[k].kind = V4_WIRE_NONE; p->wire[k].node = 0; p->wire[k].port = 0; p->wire[k].device = 0; }
}

void v4_fabric_init(v4_fabric *f, v4_place *places, unsigned capacity)
{
    unsigned i;
    f->place = places;
    f->capacity = capacity;
    f->gone_error = 0;
    f->interrupt_error = 0;
    for (i = 0; i < capacity; i++) clear_place(&places[i]);
}

void v4_fabric_gone_error(v4_fabric *f, v4_cell code)
{
    f->gone_error = code;
}

void v4_fabric_interrupt_error(v4_fabric *f, v4_cell code)
{
    f->interrupt_error = code;
}

void v4_fabric_grow(v4_fabric *f, v4_place *places, unsigned capacity)
{
    unsigned i;
    if (capacity < f->capacity) return;
    for (i = 0; i < f->capacity; i++) places[i] = f->place[i];
    for (; i < capacity; i++) clear_place(&places[i]);
    f->place = places;
    f->capacity = capacity;
}

int v4_fabric_add(v4_fabric *f, v4_fabric_node *storage, v4_cell port_base)
{
    unsigned i;
    for (i = 0; i < f->capacity && f->place[i].node; i++) { }
    if (i == f->capacity || !storage) return -1;
    clear_place(&f->place[i]);
    f->place[i].node = storage;
    v4_node_born(&storage->n, port_base);
    v4_exec_reset(&storage->es);
    v4_heat_reset(&storage->h);
    return (int)i;
}

v4_fabric_node *v4_fabric_node_at(const v4_fabric *f, unsigned id)
{
    return id < f->capacity ? f->place[id].node : 0;
}

static int there(const v4_fabric *f, unsigned id, unsigned port)
{
    return id < f->capacity && f->place[id].node && port < V4_PORTS;
}

/* cut what is on a port, at both ends */
static void cut(v4_fabric *f, unsigned a, unsigned pa)
{
    v4_wire *w = &f->place[a].wire[pa];
    if (w->kind == V4_WIRE_NODE && w->node < f->capacity && w->port < V4_PORTS) {
        v4_wire *other = &f->place[w->node].wire[w->port];
        if (other->kind == V4_WIRE_NODE && other->node == a && other->port == pa) { other->kind = V4_WIRE_NONE; other->device = 0; }
    }
    w->kind = V4_WIRE_NONE;
    w->device = 0;
}

int v4_fabric_wire(v4_fabric *f, unsigned a, unsigned pa, unsigned b, unsigned pb)
{
    if (!there(f, a, pa) || !there(f, b, pb) || (a == b && pa == pb)) return 0;
    cut(f, a, pa);
    cut(f, b, pb);
    f->place[a].wire[pa].kind = V4_WIRE_NODE; f->place[a].wire[pa].node = b; f->place[a].wire[pa].port = pb;
    f->place[b].wire[pb].kind = V4_WIRE_NODE; f->place[b].wire[pb].node = a; f->place[b].wire[pb].port = pa;
    return 1;
}

int v4_fabric_wire_device(v4_fabric *f, unsigned a, unsigned pa, const v4_device *device)
{
    if (!there(f, a, pa) || !device) return 0;
    cut(f, a, pa);
    f->place[a].wire[pa].kind = V4_WIRE_DEVICE;
    f->place[a].wire[pa].device = device;
    return 1;
}

int v4_fabric_unwire(v4_fabric *f, unsigned a, unsigned pa)
{
    if (!there(f, a, pa)) return 0;
    cut(f, a, pa);
    return 1;
}

v4_fabric_node *v4_fabric_remove(v4_fabric *f, unsigned id)
{
    v4_fabric_node *storage;
    unsigned k;
    if (id >= f->capacity || !f->place[id].node) return 0;
    for (k = 0; k < V4_PORTS; k++) cut(f, id, k);
    storage = f->place[id].node;
    clear_place(&f->place[id]);
    return storage;
}

void v4_fabric_sleep(v4_fabric *f, unsigned id)
{
    if (id < f->capacity && f->place[id].node) f->place[id].asleep = 1;
}

void v4_fabric_wake(v4_fabric *f, unsigned id)
{
    if (id < f->capacity && f->place[id].node) f->place[id].asleep = 0;
}

static int awake(const v4_fabric *f, unsigned id)
{
    return id < f->capacity && f->place[id].node && !f->place[id].asleep;
}

/* What node `a` wrote to one of its ports, handed to whatever is there. */
static unsigned hand_over_write(v4_fabric *f, unsigned a)
{
    v4_node *n = &f->place[a].node->n;
    const v4_wire *w = &f->place[a].wire[n->ask_port];

    if (w->kind == V4_WIRE_DEVICE) {
        if (w->device->take && w->device->take(w->device->self, n->request)) { v4_node_port_served(n); return 1; }
    } else if (w->kind == V4_WIRE_NODE && awake(f, w->node)) {
        v4_node *r = &f->place[w->node].node->n;
        if (r->reading && !r->given && (r->read_port == w->port || r->read_port == V4_PORT_ANY)) {
            v4_node_port_give(r, w->port, n->request);
            v4_node_port_served(n);
            return 1;
        }
    }
    return 0;
}

/* Node `a` is reading: a device on that port, or on any of them, is asked. */
static unsigned hand_over_read(v4_fabric *f, unsigned a)
{
    v4_node *n = &f->place[a].node->n;
    unsigned first = n->read_port == V4_PORT_ANY ? 0 : n->read_port;
    unsigned last  = n->read_port == V4_PORT_ANY ? V4_PORTS - 1 : n->read_port;
    unsigned k;
    v4_cell value;

    for (k = first; k <= last; k++) {
        const v4_wire *w = &f->place[a].wire[k];
        if (w->kind == V4_WIRE_DEVICE && w->device->give && w->device->give(w->device->self, &value)) {
            v4_node_port_give(n, k, value);
            return 1;
        }
    }
    return 0;
}

/* What node `a` can see of its neighbours before it executes: who is
 * blocked writing to it, and who would take a word from it.  A device is
 * always ready to be written to; what it has to give, the node finds when
 * it reads. */
static void look_about(v4_fabric *f, unsigned a)
{
    unsigned k, writers = 0, readers = 0;

    for (k = 0; k < V4_PORTS; k++) {
        const v4_wire *w = &f->place[a].wire[k];
        if (w->kind != V4_WIRE_NONE) readers |= 1u << (V4_PORTS + k);    /* there is something on this port */
        if (w->kind == V4_WIRE_DEVICE) {
            if (w->device->take) readers |= 1u << k;
        } else if (w->kind == V4_WIRE_NODE && awake(f, w->node)) {
            const v4_node *o = &f->place[w->node].node->n;
            if (o->asking && o->ask_port == w->port) writers |= 1u << k;
            if (o->reading && !o->given && (o->read_port == w->port || o->read_port == V4_PORT_ANY)) readers |= 1u << k;
        }
    }
    v4_node_port_status(&f->place[a].node->n, writers, readers);
}

unsigned v4_fabric_step(v4_fabric *f)
{
    unsigned i, done = 0;

    /* a node that is blocked fetches nothing, and is looked about for when
     * it is next to execute */
    for (i = 0; i < f->capacity; i++)
        if (awake(f, i)) {
            const v4_node *n = &f->place[i].node->n;
            if (!n->stopped && !n->asking && !(n->reading && !n->given)) look_about(f, i);
        }

    for (i = 0; i < f->capacity; i++)
        if (awake(f, i)) done += v4_exec_step_word(&f->place[i].node->n, &f->place[i].node->es, &f->place[i].node->h);

    for (i = 0; i < f->capacity; i++)
        if (awake(f, i) && f->place[i].node->n.asking) done += hand_over_write(f, i);
    for (i = 0; i < f->capacity; i++)
        if (awake(f, i) && f->place[i].node->n.reading && !f->place[i].node->n.given) done += hand_over_read(f, i);

    /* THE WAIT (docs/v4.0.0/MESH.md 7c).  A node in the wait that was given a
     * word above is no longer in it: a word for a node comes before its own
     * offer.  Of the rest, each offer is taken by whoever is ready for it: a
     * device that takes, or a node blocked reading that port or any -- which
     * a node in the wait is, so of two that offer to each other the one at
     * the lower place writes and the other's offers are withdrawn. */
    for (i = 0; i < f->capacity; i++) {
        v4_node *n;
        unsigned k;
        if (!awake(f, i)) continue;
        n = &f->place[i].node->n;
        if (!v4_node_in_wait(n)) continue;
        for (k = 0; k < V4_PORTS; k++) {
            const v4_wire *w = &f->place[i].wire[k];
            if (!(n->offers & (1u << k))) continue;
            if (w->kind == V4_WIRE_DEVICE) {
                if (w->device->take && w->device->take(w->device->self, n->offer[k])) { (void)v4_node_offer_taken(n, k); done++; break; }
            } else if (w->kind == V4_WIRE_NODE && awake(f, w->node)) {
                v4_node *r = &f->place[w->node].node->n;
                if (r->reading && !r->given && (r->read_port == w->port || r->read_port == V4_PORT_ANY)) {
                    v4_cell word = n->offer[k];
                    (void)v4_node_offer_taken(n, k);
                    v4_node_port_give(r, w->port, word);
                    done++;
                    break;
                }
            }
        }
    }

    /* a node blocked on the first word of a message to a node that is not
     * reading, while a device of its own has something for it */
    if (f->interrupt_error != 0)
        for (i = 0; i < f->capacity; i++) {
            v4_node *n;
            unsigned k;
            if (!awake(f, i)) continue;
            n = &f->place[i].node->n;
            if (!n->asking || f->place[i].wire[n->ask_port].kind != V4_WIRE_NODE || v4_node_words_since_look(n) != 0) continue;
            for (k = 0; k < V4_PORTS; k++) {
                const v4_wire *w = &f->place[i].wire[k];
                if (w->kind == V4_WIRE_DEVICE && w->device->pending && w->device->pending(w->device->self)) {
                    done += (unsigned)v4_node_port_gone(n, f->interrupt_error);
                    break;
                }
            }
        }

    /* a node blocked at one port that nothing is wired to */
    if (f->gone_error != 0)
        for (i = 0; i < f->capacity; i++) {
            v4_node *n;
            if (!awake(f, i)) continue;
            n = &f->place[i].node->n;
            if ((n->asking && f->place[i].wire[n->ask_port].kind == V4_WIRE_NONE)
                || (n->reading && !n->given && n->read_port != V4_PORT_ANY && f->place[i].wire[n->read_port].kind == V4_WIRE_NONE))
                done += (unsigned)v4_node_port_gone(n, f->gone_error);
            else if (v4_node_in_wait(n)) {                    /* an offer on a port with nothing on it */
                unsigned k;
                for (k = 0; k < V4_PORTS; k++)
                    if ((n->offers & (1u << k)) && f->place[i].wire[k].kind == V4_WIRE_NONE) { done += (unsigned)v4_node_port_gone(n, f->gone_error); break; }
            }
        }

    return done;
}