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#include <assert.h>
#include <stddef.h>
#include <stdlib.h>

#include "error.h"
#include "expected.h"
#include "lexer.h"
#include "parseexpr.h"

static struct Expr *parseExpr();
static struct Expr *parseBinaryExpr(size_t priority);
static struct Expr *parseUnaryExpr();
static struct Expr *parsePrimaryExpr();

static bool
wordToken(size_t *word)
{
    assert(word);
    switch (token.kind) {
        case W0:
            *word = 0;
            return true;
        case W1:
            *word = 1;
            return true;
        case W2:
            *word = 2;
            return true;
        case W3:
            *word = 3;
            return true;
        default:
            return false;
    }
}

struct Expr *
parseExpression()
{
    size_t word = 0;
    if (wordToken(&word)) {
        struct Token op = token;
        getToken();
        expected(LPAREN);
        getToken();
        struct Expr *expr = parseExpr();
        if (!expr) {
            error("Expression expected\n");
        }
        expected(RPAREN);
        getToken();
        return makeUnaryWordExpr(op.loc, word, expr);
    }

    return parseBinaryExpr(1);
}

static struct Expr *
parseExpr()
{
    return parseBinaryExpr(1);
}

static size_t
binaryOpPriority(enum TokenKind t)
{
    switch (t) {
        case ASTERISK:
        case SLASH:
        case PERCENT:
            return 2;
        case PLUS:
        case MINUS:
            return 1;
        default:
            return 0;
    }
}

static enum ExprBinaryOperand
binaryOp(enum TokenKind t)
{
    switch (t) {
        case PLUS:
            return EO_PLUS;
        case MINUS:
            return EO_MINUS;
        case ASTERISK:
            return EO_ASTERISK;
        case SLASH:
            return EO_SLASH;
        case PERCENT:
            return EO_PERCENT;
        default:
            fprintf(stderr, "internal error in 'binaryOp'\n");
            fprintf(stderr, "unexpected token %s\n", strTokenKind(t));
            abort();
            return 0;
    }
}

static struct Expr *
parseBinaryExpr(size_t priority)
{
    struct Expr *expr = parseUnaryExpr();
    if (!expr) {
        return 0;
    }

    for (size_t p = binaryOpPriority(token.kind); p >= priority; --p) {
        while (binaryOpPriority(token.kind) == p) {
            struct Token op = token;
            getToken();
            struct Expr *right = parseBinaryExpr(p + 1);
            expr = makeBinaryExpr(op.loc, binaryOp(op.kind), expr, right);
        }
    }
    return expr;
}

static struct Expr *
parseUnaryExpr()
{
    while (token.kind == PLUS) {
        getToken();
    }
    if (token.kind == MINUS) {
        struct Token op = token;
        getToken();
        return makeUnaryMinusExpr(op.loc, parseUnaryExpr());
    }
    return parsePrimaryExpr();
}

static struct Expr *
parsePrimaryExpr()
{
    struct Expr *expr = 0;

    switch (token.kind) {
        case CHARACTER_LITERAL: {
            uint64_t val = token.processedVal.cstr[0];
            expr = makeValExpr(token.loc, ABS, val);
            getToken();
        } break;
        case DECIMAL_LITERAL:
        case OCTAL_LITERAL:
        case HEXADECIMAL_LITERAL: {
            uint64_t val = strtoll(token.val.cstr, 0, 0);
            expr = makeValExpr(token.loc, ABS, val);
            getToken();

        } break;
        case IDENT:
            expr = makeSymExpr(token.loc, makeUStr(token.val.cstr));
            getToken();
            break;
        case LPAREN:
            getToken();
            expr = parseExpr();
            expected(RPAREN);
            getToken();
        default:;
    }

    return expr;
}