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

#include "alloc.h"
#include "repl.h"

struct repl_data {
    apfl_ctx ctx;
    struct apfl_allocator alloc;
    char *buf;
    size_t buf_len;
    size_t buf_cap;
    struct apfl_io_writer w_out;
    struct apfl_io_writer w_err;
};

static bool
null_writer(void *opaque, const unsigned char *buf, size_t len)
{
    (void)opaque;
    (void)buf;
    (void)len;
    return true;
}

static bool
redirect_writer(void *opaque, const unsigned char *buf, size_t len)
{
    repl r = opaque;
    return r->w_out.write(r->w_out.opaque, buf, len);
}

repl
repl_new(struct apfl_allocator alloc)
{
    repl r = ALLOC_OBJ(alloc, struct repl_data);
    if (r == NULL) {
        return NULL;
    }

    r->alloc = alloc;
    r->buf = NULL;
    r->buf_len = 0;
    r->buf_cap = 0;
    r->w_out = (struct apfl_io_writer){.write = null_writer};
    r->w_err = (struct apfl_io_writer){.write = null_writer};

    r->ctx = apfl_ctx_new((struct apfl_config) {
        .allocator = alloc,
        .output_writer = (struct apfl_io_writer){.write = redirect_writer, .opaque = r},
    });

    if (r->ctx == NULL) {
        repl_destroy(r);
        return NULL;
    }

    return r;
}

void
repl_set_w_out(repl r, struct apfl_io_writer w)
{
    r->w_out = w;
}

void
repl_set_w_err(repl r, struct apfl_io_writer w)
{
    r->w_err = w;
}

static void
protected_callback(apfl_ctx ctx, void *opaque)
{
    (void)opaque;
    apfl_run_in_top_scope(ctx, -1);
}

static enum repl_result
report_error(repl r, struct apfl_error error)
{
    apfl_error_print(error, r->w_err);
    return (error.type == APFL_ERR_MALLOC_FAILED || error.type == APFL_ERR_INPUT_ERROR)
        ? REPL_FATAL
        : REPL_ERR;
}

enum repl_result
repl_run(repl r, char *input)
{
    if (input != NULL) {
        size_t input_len = strlen(input);
        size_t needed = r->buf_len + input_len;
        if (r->buf_cap < needed) {
            char *newbuf = REALLOC_BYTES(r->alloc, r->buf, r->buf_cap, needed);
            if (newbuf == NULL) {
                return REPL_FATAL;
            }
            r->buf = newbuf;
            r->buf_cap = needed;
        }

        memcpy(r->buf + r->buf_len, input, input_len);
        r->buf_len += input_len;
    }

    struct apfl_io_string_reader_data sr = apfl_io_string_reader_create(
        (struct apfl_string_view) {
            (unsigned char *)r->buf,
            r->buf_len,
        }
    );

    struct apfl_error error;
    apfl_push_const_string(r->ctx, "<toplevel>");
    if (!apfl_load_try(r->ctx, apfl_io_string_reader(&sr), -1, &error)) {
        if (
            error.type == APFL_ERR_UNEXPECTED_EOF
            || error.type == APFL_ERR_UNEXPECTED_EOF_AFTER_TOKEN
        ) {
            if (input == NULL) {
                (void)report_error(r, error);
                return REPL_FATAL;
            } else {
                return REPL_MORE_INPUT;
            }
        } else {
            return report_error(r, error);
        }
    }

    r->buf_len = 0;

    switch (apfl_do_protected(r->ctx, protected_callback, NULL, apfl_error_decorate_with_backtrace)) {
    case APFL_RESULT_OK :
        if (apfl_get_type(r->ctx, -1) == APFL_VALUE_NIL) {
            apfl_drop(r->ctx, -1);
        } else {
            apfl_debug_print_val(r->ctx, -1, r->w_out);
        }
        return REPL_OK;
    case APFL_RESULT_ERR:
        apfl_io_write_string(r->w_err, "Error occurred during evaluation:\n");
        if (apfl_get_type(r->ctx, -1) == APFL_VALUE_STRING) {
            apfl_io_write_string(r->w_err, apfl_get_string(r->ctx, -1));
            apfl_drop(r->ctx, -1);
        } else {
            apfl_debug_print_val(r->ctx, -1, r->w_err);
        }
        apfl_io_write_byte(r->w_err, '\n');
        return REPL_ERR;
    case APFL_RESULT_ERRERR:
        apfl_io_write_string(r->w_err, "Error occurred during error handling.\n");
        return REPL_FATAL;
    case APFL_RESULT_ERR_ALLOC:
        apfl_io_write_string(r->w_err, "Fatal: Could not allocate memory.\n");
        return REPL_FATAL;
    }

    assert(false && "unreachable");
    return REPL_FATAL;
}

void
repl_destroy(repl r)
{
    apfl_ctx_destroy(r->ctx);
    FREE_BYTES(r->alloc, r->buf, r->buf_cap);
    FREE_OBJ(r->alloc, r);
}