/* 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;
    p->cut = 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;
        p->wire[k].rx = 0; p->wire[k].tx = 0;
    }
}

void v4_fabric_init(v4_fabric *f, v4_place *places, unsigned capacity)
{
    unsigned i;
    f->place = places;
    f->capacity = capacity;
    f->queue = 0;
    f->queue_count = 0;
    f->queue_free = 0;
    f->queue_first = 0;
    f->gone_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_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;
}

void v4_fabric_queues(v4_fabric *f, v4_wire_queue *pool, unsigned count)
{
    unsigned i;
    f->queue = pool;
    f->queue_count = count;
    f->queue_free = count;
    f->queue_first = count ? 1 : 0;
    for (i = 0; i < count; i++) {
        v4_wire_reset(&pool[i]);
        pool[i].head = i + 1 < count ? i + 2 : 0;
    }
}

/* a queue that is not on a wire; the fabric has been given some, and there is one */
static v4_wire_queue *take_queue(v4_fabric *f)
{
    v4_wire_queue *q = &f->queue[f->queue_first - 1];
    f->queue_first = q->head;
    f->queue_free--;
    v4_wire_reset(q);
    return q;
}

/* a queue comes off a wire: what was waiting on it is let go */
static void give_queue(v4_fabric *f, v4_wire_queue *q)
{
    if (!q) return;
    v4_wire_reset(q);
    q->head = f->queue_first;
    f->queue_first = (unsigned)(q - f->queue) + 1;
    f->queue_free++;
}

/* Can the ports a and b be wired: if the fabric has been given queues, are
 * there two once what those ports are wired to now has been given back? */
static int queues_for(const v4_fabric *f, unsigned a, unsigned pa, unsigned b, unsigned pb)
{
    const v4_wire_queue *seen[4];
    unsigned i, k, n = 0, back = 0;

    if (!f->queue) return 1;
    seen[n++] = f->place[a].wire[pa].rx; seen[n++] = f->place[a].wire[pa].tx;
    if (b < f->capacity) { seen[n++] = f->place[b].wire[pb].rx; seen[n++] = f->place[b].wire[pb].tx; }
    for (i = 0; i < n; i++) {
        if (!seen[i]) continue;
        for (k = 0; k < i && seen[k] != seen[i]; k++) { }
        if (k == i) back++;
    }
    return f->queue_free + back >= 2;
}

/* 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;
            other->rx = 0; other->tx = 0;                    /* the same two queues as w's */
            f->place[w->node].cut = 1;
        }
    }
    if (w->kind != V4_WIRE_NONE) f->place[a].cut = 1;        /* a node asleep for room on another wire is woken (operation 9) */
    if (f->queue) { give_queue(f, w->rx); give_queue(f, w->tx); }
    w->kind = V4_WIRE_NONE;
    w->device = 0;
    w->rx = 0;
    w->tx = 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;
    if (!queues_for(f, a, pa, b, 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;
    if (f->queue) {
        v4_wire_queue *ab = take_queue(f), *ba = take_queue(f);
        f->place[a].wire[pa].tx = ab; f->place[b].wire[pb].rx = ab;
        f->place[b].wire[pb].tx = ba; f->place[a].wire[pa].rx = ba;
    }
    return 1;
}

int v4_fabric_wire_kernel(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;      /* and no queues: it takes no messages */
    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;
    if (!queues_for(f, a, pa, f->capacity, 0)) return 0;
    cut(f, a, pa);
    f->place[a].wire[pa].kind = V4_WIRE_DEVICE;
    f->place[a].wire[pa].device = device;
    if (f->queue) {
        f->place[a].wire[pa].rx = take_queue(f);             /* from the device */
        f->place[a].wire[pa].tx = take_queue(f);             /* to it */
    }
    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;
}

int v4_fabric_device_put(v4_fabric *f, unsigned node, unsigned port, const v4_cell *header7, const v4_cell *text)
{
    const v4_wire *w;
    if (!there(f, node, port)) return V4_WIRE_NO_ONE;
    w = &f->place[node].wire[port];
    if (w->kind != V4_WIRE_DEVICE || !w->rx) return V4_WIRE_NO_ONE;
    return v4_wire_put(w->rx, header7, text);
}

int v4_fabric_device_take(v4_fabric *f, unsigned node, unsigned port, v4_cell *header7, v4_cell *text, unsigned text_cap)
{
    const v4_wire *w;
    if (!there(f, node, port)) return V4_WIRE_NO_ONE;
    w = &f->place[node].wire[port];
    if (w->kind != V4_WIRE_DEVICE || !w->tx) return V4_WIRE_NO_ONE;
    v4_wire_first(w->tx);                                    /* the device takes them in the order they were put */
    return v4_wire_take(w->tx, header7, text, text_cap);
}

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;
}

/* 1 if a word written to this end of a wire will not be read: the other end
 * is a device that takes no words, or a node that speaks whole messages --
 * one that has asked for a whole-message operation since it was born. */
static int no_reader(const v4_fabric *f, const v4_wire *w)
{
    if (w->kind == V4_WIRE_DEVICE) return w->device->take == 0;
    if (w->kind == V4_WIRE_NODE && w->node < f->capacity && f->place[w->node].node) return f->place[w->node].node->n.spoke != 0;
    return 0;
}

/* 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);
}

/* ---- whole messages: what a node asked for by storing to Do (MESH.md 7d.3) ---- */

/* 1 if `count` words from `addr` are memory that is not the ports, or the
 * addresses after them, of this node: they may be copied to and from. */
static int span_ok(const v4_node *n, v4_cell addr, unsigned count)
{
    if (count == 0) return 1;
    if (count > V4_NODE_WORDS || addr < 0 || (v4_ucell)addr > (v4_ucell)(V4_NODE_WORDS - count)) return 0;
    if (n->port >= 0 && addr <= n->port + (v4_cell)V4_PORT_HAVE && addr + (v4_cell)count > n->port) return 0;
    return 1;
}

/* the queue of messages that come to the node's wire, and that go from it; 0: no one is on it */
static v4_wire_queue *coming(const v4_fabric *f, unsigned id, unsigned port)
{
    return port < V4_PORTS ? f->place[id].wire[port].rx : 0;
}
static v4_wire_queue *going(const v4_fabric *f, unsigned id, unsigned port)
{
    return port < V4_PORTS ? f->place[id].wire[port].tx : 0;
}

/* has a message come to any of the node's wires since it last fetched which have one */
static int arrived(const v4_fabric *f, unsigned id)
{
    unsigned k;
    for (k = 0; k < V4_PORTS; k++) {
        const v4_wire_queue *q = f->place[id].wire[k].rx;
        if (q && q->arrived) return 1;
    }
    return 0;
}

/* has a message come off any of the wires that lead from the node since it was last woken by that */
static int freed(const v4_fabric *f, unsigned id)
{
    unsigned k;
    for (k = 0; k < V4_PORTS; k++) {
        const v4_wire_queue *q = f->place[id].wire[k].tx;
        if (q && q->freed) return 1;
    }
    return 0;
}

/* Node `id` is doing an operation.  Returns 1 and puts how it went in
 * *how, or returns 0: it waits (8 and 9 only).  Nothing is copied, put or
 * taken unless the answer is 0 -- done. */
static int operate(v4_fabric *f, unsigned id, v4_cell *how)
{
    v4_node *n = &f->place[id].node->n;
    v4_wire_queue *rx = coming(f, id, n->wire), *tx = going(f, id, n->wire), *to;
    v4_cell a = n->wire_a, b = n->wire_b, h[V4_WIRE_HEADER];
    unsigned cells;

    switch (n->do_op) {
    case 1:                                                  /* look */
        if (!rx) { *how = V4_WIRE_NO_ONE; break; }
        if (rx->mark >= rx->used) { *how = V4_WIRE_NO_MESSAGE; break; }
        if (!span_ok(n, a, V4_WIRE_HEADER)) { *how = V4_WIRE_NOT_A_MESSAGE; break; }
        *how = v4_wire_look(rx, &n->mem[a]);
        break;
    case 2:                                                  /* take */
        if (!rx) { *how = V4_WIRE_NO_ONE; break; }
        if (rx->mark >= rx->used || !rx->looked) { *how = V4_WIRE_NO_MESSAGE; break; }   /* only the message last looked at (wire.h) */
        (void)v4_wire_look(rx, h);
        cells = v4_wire_cells(h[6]) - V4_WIRE_HEADER;
        if (!span_ok(n, a, V4_WIRE_HEADER) || !span_ok(n, b, cells)) { *how = V4_WIRE_NOT_A_MESSAGE; break; }
        *how = v4_wire_take(rx, &n->mem[a], cells ? &n->mem[b] : &n->mem[0], cells);
        break;
    case 3:                                                  /* move */
        if (!rx) { *how = V4_WIRE_NO_ONE; break; }
        if (rx->mark >= rx->used || !rx->looked) { *how = V4_WIRE_NO_MESSAGE; break; }
        to = a >= 0 && a < (v4_cell)V4_PORTS ? going(f, id, (unsigned)a) : 0;
        *how = to ? v4_wire_move(rx, to) : V4_WIRE_NO_ONE;
        break;
    case 4:                                                  /* drop */
        *how = !rx ? V4_WIRE_NO_ONE : rx->looked ? v4_wire_drop(rx) : V4_WIRE_NO_MESSAGE;
        break;
    case 5:                                                  /* put */
        if (!tx) { *how = V4_WIRE_NO_ONE; break; }
        if (!span_ok(n, a, V4_WIRE_HEADER)) { *how = V4_WIRE_NOT_A_MESSAGE; break; }
        cells = v4_wire_cells(n->mem[a + 6]);
        if (cells == 0 || !span_ok(n, b, cells - V4_WIRE_HEADER)) { *how = V4_WIRE_NOT_A_MESSAGE; break; }
        *how = v4_wire_put(tx, &n->mem[a], cells > V4_WIRE_HEADER ? &n->mem[b] : &n->mem[0]);
        break;
    case 6:                                                  /* first */
        if (rx) v4_wire_first(rx);
        *how = rx ? V4_WIRE_DONE : V4_WIRE_NO_ONE;
        break;
    case 7:                                                  /* next */
        *how = rx ? v4_wire_next(rx) : V4_WIRE_NO_ONE;
        break;
    case 8:                                                  /* sleep */
        if (!arrived(f, id)) return 0;
        *how = V4_WIRE_DONE;
        break;
    case 9:                                                  /* sleep for room */
        if (!tx) { *how = V4_WIRE_NO_ONE; break; }
        if (a < 0 || a > (v4_cell)V4_WIRE_CELLS) { *how = V4_WIRE_NO_ROOM; break; }   /* no waiting can make that room */
        if (v4_wire_room(tx, (unsigned)a) == V4_WIRE_DONE) { *how = V4_WIRE_DONE; break; }
        if (!arrived(f, id) && !freed(f, id) && !f->place[id].cut) return 0;
        f->place[id].cut = 0;
        for (cells = 0; cells < V4_PORTS; cells++)                 /* woken: the room that has come on any of its wires is seen */
            if (f->place[id].wire[cells].tx) f->place[id].wire[cells].tx->freed = 0;
        *how = V4_WIRE_NO_ROOM;
        break;
    case 10:                                                 /* room */
        if (!tx) { *how = V4_WIRE_NO_ONE; break; }
        if (a < 0) { *how = V4_WIRE_NOT_A_MESSAGE; break; }
        *how = a <= (v4_cell)V4_WIRE_CELLS ? v4_wire_room(tx, (unsigned)a) : V4_WIRE_NO_ROOM;
        break;
    default:                                                 /* not an operation */
        *how = V4_WIRE_NOT_A_MESSAGE;
        break;
    }
    return 1;
}

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

    /* which of its wires have a message waiting, for each node to fetch */
    for (i = 0; i < f->capacity; i++)
        if (awake(f, i)) {
            unsigned have = 0;
            for (k = 0; k < V4_PORTS; k++) {
                const v4_wire_queue *q = f->place[i].wire[k].rx;
                if (q && q->used > 0) have |= 1u << k;
            }
            v4_node_have(&f->place[i].node->n, have);
        }

    /* 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->doing && !(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);

    /* a node that fetched which wires have a message has seen what had come */
    for (i = 0; i < f->capacity; i++)
        if (awake(f, i) && f->place[i].node->n.have_fetched) {
            for (k = 0; k < V4_PORTS; k++)
                if (f->place[i].wire[k].rx) f->place[i].wire[k].rx->arrived = 0;
            f->place[i].node->n.have_fetched = 0;
        }

    /* the operations on the wires, each whole; the two that wait are looked at last, so that
     * what every other node has put or taken this step has been, whatever their numbers */
    for (i = 0; i < f->capacity; i++)
        if (awake(f, i) && f->place[i].node->n.doing && f->place[i].node->n.do_op != 8 && f->place[i].node->n.do_op != 9) {
            v4_cell how;
            (void)operate(f, i, &how);
            v4_node_done(&f->place[i].node->n, how);
            done++;
        }
    for (i = 0; i < f->capacity; i++)
        if (awake(f, i) && f->place[i].node->n.doing) {
            v4_cell how;
            if (operate(f, i, &how)) { v4_node_done(&f->place[i].node->n, how); done++; }
        }

    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);

    /* a node blocked at one port that nothing is wired to; or blocked writing a
     * word to what will not read one (fabric.h, A WORD NO ONE WILL READ) */
    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 || no_reader(f, &f->place[i].wire[n->ask_port])))
                || (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);
        }

    return done;
}