#include <string.h>
#include "proc.h"
#include "peephole.h"

/* procedures */

/* the tangle of arenas here will need to be sorted out eventually: currently
 * we have two arenas for every single procedure, a permanent one lasting the
 * full length of compilation, and a scratch arena reset after every statement.
 * so, long-lasting node data and very temporary allocations.
 *
 * this works fine when there's just one procedure, but long-term there should
 * be a couple arenas per _worker thread_, not per procedure.  and for this,
 * there's a third kind of data --- stuff that lasts the length of parsing one
 * procedure, but no longer; scope information, mainly.
 *
 * so in the end we might have like
 * _Thread_local Arena graph_arena, scratch_arena, parse_arena;
 */

void proc_init(Proc *proc, Str name) {
	memset(proc, 0, sizeof(Proc));
	Graph *g = &proc->graph;
	proc->pool.arena = &proc->perm;
	proc->scope.arena = &proc->perm;
	g->pool = &proc->pool;
	g->start = node_new(g, N_START, NULL);
	g->start->type = (Type) {
		.lvl = T_BOT,
		.t = T_TUPLE,
		.next = NULL
	};
	g->stop = node_new_empty(g, N_STOP);
	g->ctrl = g->start;
	g->keepalive = node_new(g, N_KEEPALIVE, NULL);
	proc->name = name;
}

void proc_free(Proc *proc) {
	arena_free(&proc->perm);
	arena_free(&proc->scratch);
}

/* scope */

NameBinding *scope_find(Scope *scope, Str name) {
	for (ScopeFrame *f = scope->tail; f; f = f->prev) {
		for (NameBinding *b = f->latest; b; b = b->prev) {
			if (str_eql(b->name, name)) {
				return b;
			}
		}
	}
	return NULL;
}

ScopeFrame *scope_push(Scope *scope) {
	ScopeFrame *f;
	if (scope->free_scope) {
		f = scope->free_scope;
		*f = (ScopeFrame) { 0 };
		scope->free_scope = f->prev;
	} else {
		f = new(scope->arena, ScopeFrame);
	}
	f->prev = scope->tail;
	scope->tail = f;
	return f;
}

ScopeFrame *scope_pop(Scope *scope, Graph *g) {
	ScopeFrame *f = scope->tail;
	scope->tail = f->prev;
	f->prev = scope->free_scope;
	scope->free_scope = f;
	for (NameBinding *b = f->latest; b; ) {
		NameBinding *p = b->prev;
		b->prev = scope->free_bind;
		scope->free_bind = b;
		node_remove(g, b->node, g->keepalive);
		b = p;
	}
	return scope->tail;
}

/* returns previous value */
NameBinding *scope_bind(Scope *scope, Str name, Node *value, LexSpan pos, Graph *g) {
	NameBinding *prev = scope_find(scope, name);
	NameBinding *b;
	if (scope->free_bind) {
		b = scope->free_bind;
		*b = (NameBinding) { 0 };
		scope->free_bind = b->prev;
	} else {
		b = new(scope->arena, NameBinding);
	}
	b->nestlvl = scope->nestlvl;
	b->name = name;
	b->prev = scope->tail->latest;
	scope->tail->latest = b;
	b->node = value;
	b->src_pos = pos;
	node_add(g, value, g->keepalive);
	return prev;
}

NameBinding *scope_update(Scope *scope, NameBinding *b, Node *to, Graph *g) {
	Node *n = b->node;
	unsigned nestlvl = scope->nestlvl;
	for (ScopeChangeList *l = scope->changes; l; l = l->prev) {
		if (b->nestlvl < nestlvl) {
			scope_changelist_update(l, b, n, to, g);
		}
		nestlvl--;
	}
	node_add(g, to, g->keepalive);
	b->node = to;
	node_remove(g, n, g->keepalive);
	return b;
}

void scope_changelist_update(ScopeChangeList *l, NameBinding *b, Node *from, Node *to, Graph *g) {
	for (unsigned i = 0; i < l->n; i++) {
		ScopeChange *chg = XAR_GET(l, i);
		if (chg->bind == b) {
			node_add(g, to, g->keepalive);
			node_remove(g, chg->to, g->keepalive);
			chg->to = to;
			return;
		}
	}
	ScopeChange *chg = XAR_PUT(l, l->n++, l->arena);
	node_add(g, from, g->keepalive);
	node_add(g, to, g->keepalive);
	chg->bind = b;
	chg->from = from;
	chg->to = to;
}

void scope_changelist_push(Scope *scope, ScopeChangeList *l, Arena *a) {
	l->arena = a;
	l->prev = scope->changes;
	scope->changes = l;
	scope->nestlvl++;
}

void scope_changelist_pop(Scope *scope, Graph *g) {
	ScopeChangeList *l = scope->changes;
	scope->changes = l->prev;
	scope->nestlvl--;
	for (unsigned i = 0; i < l->n; i++) {
		ScopeChange *chg = XAR_GET(l, i);
		scope_update(scope, chg->bind, chg->from, g);
	}
}

#include <assert.h>
#include <stdio.h>
/* TODO: implement merge, probably will need scratch arena to build up
 * a Xar of something like struct { NameBinding *b; Node *y, *n; }. if
 * no match for the given bind is found in the opposite change list,
 * it gets the "from" value found in the other.
 **/
typedef struct {
	NameBinding *b;
	Node *y, *n;
} MergeChange;
void scope_changelist_merge(Scope *scope, Lexer *l, ScopeChangeList *y, ScopeChangeList *n, Node *region, Graph *graph, Arena *scratch) {
	MergeChange *m = new_arr(scratch, MergeChange, y->n + n->n);
	unsigned c = 0;
	for (unsigned i = 0; i < y->n; i++) {
		ScopeChange *chg = XAR_GET(y, i);
		m[c].b = chg->bind;
		m[c].y = chg->to;
		m[c].n = chg->from;
		c++;
	}
	unsigned yc = c;
	for (unsigned i = 0; i < n->n; i++) {
		ScopeChange *chg = XAR_GET(n, i);
		for (unsigned j = 0; j < yc; j++) {
			if (m[j].b == chg->bind) {
				m[j].n = chg->to;
				goto next;
			}
		}
		m[c].b = chg->bind;
		m[c].y = chg->from;
		m[c].n = chg->to;
		c++;
next:;
	}
	for (unsigned i = 0; i < c; i++) {
		Node *phi = node_new(graph, N_PHI, region, m[i].y, m[i].n);
		phi = node_peephole(phi, graph, l);
		scope_update(scope, m[i].b, phi, graph);
	}
}

void scope_changelist_discard(ScopeChangeList *l, Graph *g) {
	for (unsigned i = 0; i < l->n; i++) {
		ScopeChange *chg = XAR_GET(l, i);
		node_remove(g, chg->from, g->keepalive);
		node_remove(g, chg->to, g->keepalive);
	}
}