#include <assert.h>
#include <stdio.h>

#include "apfl.h"

#include "context.h"
#include "globals.h"
#include "scope.h"

#define TRY_FORMAT(ctx, x)                                                          \
    do {                                                                            \
        if (!(x)) {                                                                 \
            apfl_raise_const_error((ctx), APFL_RESULT_ERR, apfl_messages.io_error); \
        }                                                                           \
    } while (0)

static void
call_then_or_else(apfl_ctx ctx, size_t arg)
{
    apfl_get_list_member_by_index(ctx, 0, arg);
    apfl_list_create(ctx, 0);
    apfl_call(ctx, -2, -1);
}

static void
impl_if(apfl_ctx ctx)
{
    size_t len = apfl_len(ctx, 0);

    if (len < 2) {
        apfl_raise_const_error(ctx, APFL_RESULT_ERR, "if needs at least 2 arguments");
    }

    size_t i = 0;
    while (i+1 < len) {
        size_t cond = i++;
        size_t then = i++;

        apfl_get_list_member_by_index(ctx, 0, cond);
        if (apfl_get_type(ctx, -1) == APFL_VALUE_FUNC) {
            apfl_list_create(ctx, 0);
            apfl_call(ctx, -2, -1);
        }

        if (apfl_is_truthy(ctx, -1)) {
            apfl_get_list_member_by_index(ctx, 0, then);
            apfl_list_create(ctx, 0);
            apfl_call(ctx, -2, -1);
            return;
        }
    }

    if (i == len) {
        // Empty else. Return nil
        apfl_push_nil(ctx);
    } else {
        assert(i+1 == len /*exactly one argument remains as final else*/);

        call_then_or_else(ctx, i);
    }
}

static void
impl_eq(apfl_ctx ctx)
{
    size_t len = apfl_len(ctx, 0);
    if (len < 2) {
        apfl_raise_const_error(ctx, APFL_RESULT_ERR, "== needs at least 2 arguments");
    }

    for (size_t i = 0; i < len-1; i++) {
        apfl_get_list_member_by_index(ctx, 0, i);
        apfl_get_list_member_by_index(ctx, 0, i+1);
        if (!apfl_eq(ctx, -2, -1)) {
            apfl_push_bool(ctx, false);
            return;
        }
    }

    apfl_push_bool(ctx, true);
}

#define IMPL_MATH_OP(name, op)                       \
    static apfl_number                               \
    name(apfl_ctx ctx, apfl_number a, apfl_number b) \
    {                                                \
        (void)ctx;                                   \
        return a op b;                               \
    }

#define IMPL_MATH_OP_FUNC(impl, name, single, op)                                            \
    static void                                                                              \
    impl(apfl_ctx ctx)                                                                       \
    {                                                                                        \
        size_t len = apfl_len(ctx, 0);                                                       \
        if (len < 1) {                                                                       \
            apfl_raise_const_error(ctx, APFL_RESULT_ERR, name " needs at least 1 argument"); \
        }                                                                                    \
                                                                                             \
        apfl_get_list_member_by_index(ctx, 0, 0);                                            \
        apfl_number num = apfl_get_number(ctx, -1);                                          \
        if (len == 1) {                                                                      \
            single(num);                                                                     \
            return;                                                                          \
        }                                                                                    \
                                                                                             \
        for (size_t i = 1; i < len; i++) {                                                   \
            apfl_get_list_member_by_index(ctx, 0, i);                                        \
            num = op(ctx, num, apfl_get_number(ctx, -1));                                    \
        }                                                                                    \
                                                                                             \
        apfl_push_number(ctx, num);                                                          \
    }

static apfl_number
single_identity(apfl_number number)
{
    return number;
}

static apfl_number
single_negate(apfl_number number)
{
    return -number;
}

IMPL_MATH_OP(op_plus, +)
IMPL_MATH_OP(op_minus, -)
IMPL_MATH_OP(op_mult, *)
IMPL_MATH_OP_FUNC(impl_plus,  "+", single_identity, op_plus)
IMPL_MATH_OP_FUNC(impl_minus, "-", single_negate,   op_minus)
IMPL_MATH_OP_FUNC(impl_mult,  "*", single_identity, op_mult)

static apfl_number
op_div(apfl_ctx ctx, apfl_number a, apfl_number b)
{
    if (b == 0.0 || b == -0.0) { // apfl_number is a double, so there are technically two zeroes :/
        apfl_raise_const_error(ctx, APFL_RESULT_ERR, "Division by zero");
    }
    return a / b;
}

IMPL_MATH_OP_FUNC(impl_div,   "/", single_identity, op_div)

static void
print(apfl_ctx ctx)
{
    struct apfl_format_writer w = apfl_format_file_writer(stdout);

    size_t len = apfl_len(ctx, 0);
    for (size_t i = 0; i < len; i++) {
        if (i > 0) {
            TRY_FORMAT(ctx, apfl_format_put_string(w, " "));
        }

        apfl_get_list_member_by_index(ctx, 0, i);
        struct apfl_string_view sv = apfl_get_string(ctx, -1);
        TRY_FORMAT(ctx, apfl_format_put_string(w, sv));
        apfl_drop(ctx, -1);
    }

    if (len > 0) {
        TRY_FORMAT(ctx, apfl_format_put_string(w, "\n"));
    }

    apfl_push_nil(ctx);
}

static void
dump(apfl_ctx ctx)
{
    struct apfl_format_writer w = apfl_format_file_writer(stdout);
    apfl_get_list_member_by_index(ctx, 0, 0);
    apfl_drop(ctx, 0);
    TRY_FORMAT(ctx, apfl_debug_print_val(ctx, -1, w));
}

static const struct global_def globals[] = {
    {"if", impl_if},
    {"==", impl_eq},
    {"+", impl_plus},
    {"-", impl_minus},
    {"*", impl_mult},
    {"/", impl_div},
    {"print", print},
    {"dump", dump},
    {NULL, NULL},
};

const struct global_def *
apfl_globals(void)
{
    return globals;
}