/**
 * @file grammar.c
 * @brief Implements token and AST leaf construction.
 */

#include <inttypes.h>
#include <stdio.h>
#include <string.h>

#include <akerror.h>
#include <akstdlib.h>

#include <akbasic/error.h>
#include <akbasic/grammar.h>

/* Copy into a leaf's inline identifier/literal buffer, refusing truncation. */
static akerr_ErrorContext *copy_bounded(char *dest, const char *src, const char *what)
{
    PREPARE_ERROR(errctx);
    size_t srclen = 0;

    FAIL_ZERO_RETURN(errctx, (src != NULL), AKERR_NULLPOINTER, "NULL %s", what);
    PASS(errctx, aksl_strlen(src, &srclen));
    FAIL_ZERO_RETURN(errctx, (srclen < AKBASIC_MAX_STRING_LENGTH),
		     AKBASIC_ERR_VALUE,
		     "%s of %zu characters exceeds the %d character limit",
		     what, srclen, AKBASIC_MAX_STRING_LENGTH - 1);
    /* aksl_strcpy always terminates and refuses rather than truncates, which is
       the behaviour this site already wanted. The length check above stays
       because it names the limit in the message. Every destination is one of the
       leaf's AKBASIC_MAX_STRING_LENGTH buffers, which is what sizes the copy. */
    PASS(errctx, aksl_strcpy(dest, AKBASIC_MAX_STRING_LENGTH, src));
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_token_init(akbasic_Token *obj)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL token in init");
    obj->tokentype = AKBASIC_TOK_UNDEFINED;
    obj->lineno = 0;
    obj->lexeme[0] = '\0';
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_leaf_init(akbasic_ASTLeaf *obj, akbasic_LeafType leaftype)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL leaf in init");
    obj->leaftype = leaftype;
    obj->parent = NULL;
    obj->left = NULL;
    obj->right = NULL;
    obj->expr = NULL;
    obj->next = NULL;
    obj->identifier[0] = '\0';
    obj->literal_int = 0;
    obj->literal_float = 0.0;
    obj->literal_string[0] = '\0';
    obj->operator_ = AKBASIC_TOK_UNDEFINED;
    SUCCEED_RETURN(errctx);
}

/*
 * Take one leaf from the pool. Recursion in clone_into() is bounded by the pool
 * capacity, so a cyclic tree exhausts the pool and errors rather than running
 * off the stack.
 */
static akerr_ErrorContext *pool_take(akbasic_LeafPool *pool, akbasic_ASTLeaf **dest)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (pool != NULL), AKERR_NULLPOINTER, "NULL leaf pool");
    FAIL_ZERO_RETURN(errctx, (pool->leaves != NULL), AKERR_NULLPOINTER, "Leaf pool has no storage");
    FAIL_ZERO_RETURN(errctx, (pool->next < pool->capacity), AKBASIC_ERR_BOUNDS,
		     "No more leaves available");
    *dest = &pool->leaves[pool->next];
    pool->next += 1;
    SUCCEED_RETURN(errctx);
}

static akerr_ErrorContext *clone_into(akbasic_ASTLeaf *self, akbasic_LeafPool *pool, akbasic_ASTLeaf **dest)
{
    PREPARE_ERROR(errctx);
    akbasic_ASTLeaf *copy = NULL;

    if ( self == NULL ) {
	*dest = NULL;
	SUCCEED_RETURN(errctx);
    }
    PASS(errctx, pool_take(pool, &copy));
    PASS(errctx, akbasic_leaf_init(copy, self->leaftype));
    copy->parent = self->parent;
    copy->literal_int = self->literal_int;
    copy->literal_float = self->literal_float;
    PASS(errctx, aksl_memcpy(copy->literal_string, self->literal_string, sizeof(copy->literal_string)));
    PASS(errctx, aksl_memcpy(copy->identifier, self->identifier, sizeof(copy->identifier)));
    copy->operator_ = self->operator_;

    PASS(errctx, clone_into(self->left, pool, &copy->left));
    PASS(errctx, clone_into(self->right, pool, &copy->right));
    PASS(errctx, clone_into(self->expr, pool, &copy->expr));
    PASS(errctx, clone_into(self->next, pool, &copy->next));

    *dest = copy;
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_leaf_clone(akbasic_ASTLeaf *self, akbasic_LeafPool *pool, akbasic_ASTLeaf **dest)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (dest != NULL), AKERR_NULLPOINTER, "NULL destination in clone");
    PASS(errctx, clone_into(self, pool, dest));
    SUCCEED_RETURN(errctx);
}

akbasic_ASTLeaf *akbasic_leaf_first_argument(akbasic_ASTLeaf *self)
{
    if ( self == NULL ||
	 self->right == NULL ||
	 self->right->leaftype != AKBASIC_LEAF_ARGUMENTLIST ||
	 self->right->operator_ != AKBASIC_TOK_FUNCTION_ARGUMENT ) {
	return NULL;
    }
    return self->right->right;
}

akbasic_ASTLeaf *akbasic_leaf_first_subscript(akbasic_ASTLeaf *self)
{
    if ( self == NULL ||
	 self->expr == NULL ||
	 self->expr->leaftype != AKBASIC_LEAF_ARGUMENTLIST ||
	 self->expr->operator_ != AKBASIC_TOK_ARRAY_SUBSCRIPT ) {
	return NULL;
    }
    return self->expr->right;
}

bool akbasic_leaf_is_identifier(akbasic_ASTLeaf *self)
{
    return (self != NULL &&
	    (self->leaftype == AKBASIC_LEAF_IDENTIFIER ||
	     self->leaftype == AKBASIC_LEAF_IDENTIFIER_INT ||
	     self->leaftype == AKBASIC_LEAF_IDENTIFIER_FLOAT ||
	     self->leaftype == AKBASIC_LEAF_IDENTIFIER_STRING ||
	     self->leaftype == AKBASIC_LEAF_IDENTIFIER_STRUCT));
}

akbasic_Type akbasic_leaf_identifier_type(akbasic_ASTLeaf *self)
{
    if ( self == NULL ) {
	return AKBASIC_TYPE_UNDEFINED;
    }
    switch ( self->leaftype ) {
    case AKBASIC_LEAF_IDENTIFIER_INT:
	return AKBASIC_TYPE_INTEGER;
    case AKBASIC_LEAF_IDENTIFIER_FLOAT:
	return AKBASIC_TYPE_FLOAT;
    case AKBASIC_LEAF_IDENTIFIER_STRING:
	return AKBASIC_TYPE_STRING;
    case AKBASIC_LEAF_IDENTIFIER_STRUCT:
	return AKBASIC_TYPE_STRUCT;
    default:
	/* A bare identifier is a label, and a label has no storage to fill. */
	return AKBASIC_TYPE_UNDEFINED;
    }
}

bool akbasic_leaf_is_literal(akbasic_ASTLeaf *self)
{
    return (self != NULL &&
	    (self->leaftype == AKBASIC_LEAF_LITERAL_INT ||
	     self->leaftype == AKBASIC_LEAF_LITERAL_FLOAT ||
	     self->leaftype == AKBASIC_LEAF_LITERAL_STRING));
}

akerr_ErrorContext *akbasic_leaf_new_comparison(akbasic_ASTLeaf *obj, akbasic_ASTLeaf *left, akbasic_TokenType op, akbasic_ASTLeaf *right)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL leaf in new_comparison");
    FAIL_ZERO_RETURN(errctx, (left != NULL && right != NULL), AKERR_NULLPOINTER,
		     "nil pointer arguments");
    PASS(errctx, akbasic_leaf_init(obj, AKBASIC_LEAF_COMPARISON));
    obj->left = left;
    obj->right = right;
    switch ( op ) {
    case AKBASIC_TOK_LESS_THAN:
    case AKBASIC_TOK_LESS_THAN_EQUAL:
    case AKBASIC_TOK_NOT_EQUAL:
    case AKBASIC_TOK_GREATER_THAN:
    case AKBASIC_TOK_GREATER_THAN_EQUAL:
	SUCCEED_RETURN(errctx);
    default:
	FAIL_RETURN(errctx, AKBASIC_ERR_SYNTAX, "Invalid operator %d for comparison", (int)op);
    }
}

akerr_ErrorContext *akbasic_leaf_new_binary(akbasic_ASTLeaf *obj, akbasic_ASTLeaf *left, akbasic_TokenType op, akbasic_ASTLeaf *right)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL leaf in new_binary");
    FAIL_ZERO_RETURN(errctx, (left != NULL && right != NULL), AKERR_NULLPOINTER,
		     "nil pointer arguments");
    PASS(errctx, akbasic_leaf_init(obj, AKBASIC_LEAF_BINARY));
    obj->left = left;
    obj->right = right;
    obj->operator_ = op;
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_leaf_new_unary(akbasic_ASTLeaf *obj, akbasic_TokenType op, akbasic_ASTLeaf *operand)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL leaf in new_unary");
    FAIL_ZERO_RETURN(errctx, (operand != NULL), AKERR_NULLPOINTER, "nil pointer arguments");
    PASS(errctx, akbasic_leaf_init(obj, AKBASIC_LEAF_UNARY));
    /*
     * .left, not .right. An argument list chains its arguments through .right,
     * so an operand there is indistinguishable from a second argument: ABS(-9)
     * counted as two and was refused. See the note on the declaration.
     */
    obj->left = operand;
    obj->operator_ = op;
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_leaf_new_function(akbasic_ASTLeaf *obj, const char *fname, akbasic_ASTLeaf *right)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL leaf in new_function");
    PASS(errctx, akbasic_leaf_init(obj, AKBASIC_LEAF_FUNCTION));
    obj->right = right;
    obj->operator_ = AKBASIC_TOK_COMMAND;
    PASS(errctx, copy_bounded(obj->identifier, fname, "function name"));
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_leaf_new_command(akbasic_ASTLeaf *obj, const char *cmdname, akbasic_ASTLeaf *right)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL leaf in new_command");
    PASS(errctx, akbasic_leaf_init(obj, AKBASIC_LEAF_COMMAND));
    obj->right = right;
    obj->operator_ = AKBASIC_TOK_COMMAND;
    PASS(errctx, copy_bounded(obj->identifier, cmdname, "command name"));
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_leaf_new_immediate_command(akbasic_ASTLeaf *obj, const char *cmdname, akbasic_ASTLeaf *right)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL leaf in new_immediate_command");
    PASS(errctx, akbasic_leaf_init(obj, AKBASIC_LEAF_COMMAND_IMMEDIATE));
    obj->right = right;
    obj->operator_ = AKBASIC_TOK_COMMAND_IMMEDIATE;
    PASS(errctx, copy_bounded(obj->identifier, cmdname, "command name"));
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_leaf_new_branch(akbasic_ASTLeaf *obj, akbasic_ASTLeaf *expr, akbasic_ASTLeaf *trueleaf, akbasic_ASTLeaf *falseleaf)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL leaf in new_branch");
    FAIL_ZERO_RETURN(errctx, (expr != NULL), AKERR_NULLPOINTER, "nil pointer arguments");
    PASS(errctx, akbasic_leaf_init(obj, AKBASIC_LEAF_BRANCH));
    obj->expr = expr;
    obj->left = trueleaf;
    obj->right = falseleaf;
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_leaf_new_grouping(akbasic_ASTLeaf *obj, akbasic_ASTLeaf *expr)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL leaf in new_grouping");
    FAIL_ZERO_RETURN(errctx, (expr != NULL), AKERR_NULLPOINTER, "nil pointer arguments");
    PASS(errctx, akbasic_leaf_init(obj, AKBASIC_LEAF_GROUPING));
    obj->expr = expr;
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_leaf_new_literal_int(akbasic_ASTLeaf *obj, const char *lexeme)
{
    PREPARE_ERROR(errctx);
    long long value = 0;
    size_t lexlen = 0;
    int base = 10;
    int cmp = 0;

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL leaf in new_literal_int");
    FAIL_ZERO_RETURN(errctx, (lexeme != NULL), AKERR_NULLPOINTER, "NULL lexeme in new_literal_int");
    FAIL_ZERO_RETURN(errctx, (lexeme[0] != '\0'), AKBASIC_ERR_VALUE, "Empty integer literal");

    /*
     * Base 10 unless the lexeme is prefixed `0x`. The reference selects base 8
     * for *any* lexeme starting with '0' (basicgrammar.go:224), so `PRINT 010`
     * printed 8 and `PRINT 08` was a parse error -- TODO.md section 6 item 10.
     * Commodore BASIC has no octal literals, and a leading zero in a listing is
     * padding, not a radix.
     */
    PASS(errctx, aksl_strlen(lexeme, &lexlen));
    PASS(errctx, aksl_strncmp(lexeme, "0x", 2, &cmp));
    if ( lexlen > 2 && cmp == 0 ) {
	base = 16;
    }
    PASS(errctx, akbasic_leaf_init(obj, AKBASIC_LEAF_LITERAL_INT));
    PASS(errctx, aksl_strtoll(lexeme, NULL, base, &value));
    obj->literal_int = (int64_t)value;
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_leaf_new_literal_float(akbasic_ASTLeaf *obj, const char *lexeme)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL leaf in new_literal_float");
    PASS(errctx, akbasic_leaf_init(obj, AKBASIC_LEAF_LITERAL_FLOAT));
    PASS(errctx, aksl_atof(lexeme, &obj->literal_float));
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_leaf_new_literal_string(akbasic_ASTLeaf *obj, const char *lexeme)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL leaf in new_literal_string");
    PASS(errctx, akbasic_leaf_init(obj, AKBASIC_LEAF_LITERAL_STRING));
    PASS(errctx, copy_bounded(obj->literal_string, lexeme, "string literal"));
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_leaf_new_identifier(akbasic_ASTLeaf *obj, akbasic_LeafType leaftype, const char *lexeme)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL), AKERR_NULLPOINTER, "NULL leaf in new_identifier");
    PASS(errctx, akbasic_leaf_init(obj, leaftype));
    PASS(errctx, copy_bounded(obj->identifier, lexeme, "identifier"));
    SUCCEED_RETURN(errctx);
}

akerr_ErrorContext *akbasic_leaf_new_field(akbasic_ASTLeaf *obj, akbasic_ASTLeaf *base, const char *name, akbasic_TokenType operator_)
{
    PREPARE_ERROR(errctx);

    FAIL_ZERO_RETURN(errctx, (obj != NULL && base != NULL), AKERR_NULLPOINTER,
		     "NULL leaf in new_field");
    PASS(errctx, akbasic_leaf_init(obj, AKBASIC_LEAF_FIELD));
    PASS(errctx, copy_bounded(obj->identifier, name, "field name"));
    /*
     * The base hangs off `.left`, which is free for this leaf type and is where
     * a unary leaf already keeps its operand. Deliberately not `.right` or
     * `.expr`: this header's own note records three separate defects that came
     * from giving one link field two meanings, and a field chain is the fourth
     * thing that would have wanted one.
     */
    obj->left = base;
    base->parent = obj;
    obj->operator_ = operator_;
    SUCCEED_RETURN(errctx);
}

static const char *operator_to_str(akbasic_TokenType op)
{
    switch ( op ) {
    case AKBASIC_TOK_EQUAL:			return "=";
    case AKBASIC_TOK_LESS_THAN:			return "<";
    case AKBASIC_TOK_GREATER_THAN:		return ">";
    case AKBASIC_TOK_LESS_THAN_EQUAL:		return "<=";
    case AKBASIC_TOK_GREATER_THAN_EQUAL:	return ">=";
    case AKBASIC_TOK_NOT_EQUAL:			return "<>";
    case AKBASIC_TOK_PLUS:			return "+";
    case AKBASIC_TOK_MINUS:			return "-";
    case AKBASIC_TOK_STAR:			return "*";
    case AKBASIC_TOK_LEFT_SLASH:		return "/";
    case AKBASIC_TOK_CARAT:			return "^";
    case AKBASIC_TOK_NOT:			return "NOT";
    case AKBASIC_TOK_AND:			return "AND";
    case AKBASIC_TOK_OR:			return "OR";
    default:					return "";
    }
}

akerr_ErrorContext *akbasic_leaf_to_string(akbasic_ASTLeaf *self, char *dest, size_t len)
{
    PREPARE_ERROR(errctx);
    char sub1[AKBASIC_MAX_STRING_LENGTH];
    char sub2[AKBASIC_MAX_STRING_LENGTH];
    int written = 0;

    FAIL_ZERO_RETURN(errctx, (self != NULL), AKERR_NULLPOINTER, "NULL leaf in to_string");
    FAIL_ZERO_RETURN(errctx, (dest != NULL), AKERR_NULLPOINTER, "NULL destination in to_string");
    FAIL_ZERO_RETURN(errctx, (len > 0), AKBASIC_ERR_BOUNDS, "Zero-length destination in to_string");

    switch ( self->leaftype ) {
    case AKBASIC_LEAF_LITERAL_INT:
	PASS(errctx, aksl_snprintf(&written, dest, len, "%" PRId64, self->literal_int));
	break;
    case AKBASIC_LEAF_LITERAL_FLOAT:
	PASS(errctx, aksl_snprintf(&written, dest, len, "%f", self->literal_float));
	break;
    case AKBASIC_LEAF_LITERAL_STRING:
	PASS(errctx, aksl_snprintf(&written, dest, len, "%s", self->literal_string));
	break;
    case AKBASIC_LEAF_IDENTIFIER_INT:
    case AKBASIC_LEAF_IDENTIFIER_FLOAT:
    case AKBASIC_LEAF_IDENTIFIER_STRING:
    case AKBASIC_LEAF_IDENTIFIER:
	PASS(errctx, aksl_snprintf(&written, dest, len, "%s", self->identifier));
	break;
    case AKBASIC_LEAF_IDENTIFIER_STRUCT:
	PASS(errctx, aksl_snprintf(&written, dest, len, "%s", self->identifier));
	break;
    case AKBASIC_LEAF_FIELD:
	PASS(errctx, akbasic_leaf_to_string(self->left, sub1, sizeof(sub1)));
	PASS(errctx, aksl_snprintf(&written, dest, len, "%s%s%s", sub1,
				   (self->operator_ == AKBASIC_TOK_ARROW ? "->" : "."), self->identifier));
	break;
    case AKBASIC_LEAF_UNARY:
	PASS(errctx, akbasic_leaf_to_string(self->left, sub1, sizeof(sub1)));
	PASS(errctx, aksl_snprintf(&written, dest, len, "(%s %s)",
				   operator_to_str(self->operator_), sub1));
	break;
    case AKBASIC_LEAF_BINARY:
	PASS(errctx, akbasic_leaf_to_string(self->left, sub1, sizeof(sub1)));
	PASS(errctx, akbasic_leaf_to_string(self->right, sub2, sizeof(sub2)));
	PASS(errctx, aksl_snprintf(&written, dest, len, "(%s %s %s)",
				   operator_to_str(self->operator_), sub1, sub2));
	break;
    case AKBASIC_LEAF_GROUPING:
	PASS(errctx, akbasic_leaf_to_string(self->expr, sub1, sizeof(sub1)));
	PASS(errctx, aksl_snprintf(&written, dest, len, "(group %s)", sub1));
	break;
    case AKBASIC_LEAF_COMMAND:
    case AKBASIC_LEAF_COMMAND_IMMEDIATE:
    case AKBASIC_LEAF_FUNCTION:
	/*
	 * The reference falls through to Go's %+v struct dump here, which has no
	 * useful C equivalent. Print something a test can assert on instead.
	 */
	PASS(errctx, aksl_snprintf(&written, dest, len, "(%s)", self->identifier));
	break;
    default:
	PASS(errctx, aksl_snprintf(&written, dest, len, "(leaf %d)", (int)self->leaftype));
	break;
    }
    SUCCEED_RETURN(errctx);
}