/*
 * wadb, a WebAssembly debugger
 * Copyright (C) 2025 Xavier Del Campo Romero
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Affero General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Affero General Public License for more details.
 *
 * You should have received a copy of the GNU Affero General Public License
 * along with this program.  If not, see <https://www.gnu.org/licenses/>.
 */

#define _POSIX_C_SOURCE 200809L

#include <dwarf.h>
#include <libdwarf/libdwarf.h>
#include "types.h"
#include <sys/socket.h>
#include <netdb.h>
#include <unistd.h>
#include <errno.h>
#include <limits.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

enum
{
    DEBUG_EMPTY,
    DEBUG_ABBREV,
    DEBUG_INFO,
    DEBUG_STR,
    DEBUG_ARANGES,
    DEBUG_FRAME,
    DEBUG_LINE,
    DEBUG_LOC,
    DEBUG_MACINFO,
    DEBUG_PUBNAMES,
    DEBUG_PUBTYPES,
    DEBUG_RANGES,
    DEBUG_TYPES,

    NSECTIONS
};

struct dwarf
{
    FILE *f;

    struct dwsection
    {
        long offset;
        varuint32 len;
        void *data;
    } sections[NSECTIONS];
};

struct header
{
    Dwarf_Sig8 type_signature;
    Dwarf_Unsigned cu_header_length, typeoffset, next_cu_header_offset;
    Dwarf_Half version_stamp, address_size, length_size, extension_size,
        header_cu_type;
    Dwarf_Off abbrev_offset;
};

static const char *const names[NSECTIONS] =
{
    [DEBUG_EMPTY] = "",
    [DEBUG_ABBREV] = ".debug_abbrev",
    [DEBUG_ARANGES] = ".debug_aranges",
    [DEBUG_FRAME] = ".debug_frame",
    [DEBUG_INFO] = ".debug_info",
    [DEBUG_LINE] = ".debug_line",
    [DEBUG_LOC] = ".debug_loc",
    [DEBUG_MACINFO] = ".debug_macinfo",
    [DEBUG_PUBNAMES] = ".debug_pubnames",
    [DEBUG_PUBTYPES] = ".debug_pubtypes",
    [DEBUG_RANGES] = ".debug_ranges",
    [DEBUG_STR] = ".debug_str",
    [DEBUG_TYPES] = ".debug_types"
};

static void errcb(const Dwarf_Error e, const Dwarf_Ptr args)
{
}

static int get_section_info(void *const obj, const Dwarf_Half section_index,
    Dwarf_Obj_Access_Section *const return_section, int *const error)
{
    const struct dwarf *const dw = obj;

    if (section_index >= sizeof dw->sections / sizeof *dw->sections)
    {
        fprintf(stderr, "%s: invalid section_index: %hd\n", __func__,
            section_index);
        return DW_DLV_ERROR;
    }

    const struct dwsection *const s = &dw->sections[section_index];

    if (!names[section_index] && !s->len)
        return DW_DLV_NO_ENTRY;

    *return_section = (const Dwarf_Obj_Access_Section)
    {
        .size = s->len,
        .addr = s->offset,
        .name = names[section_index]
    };

    return 0;
}

static Dwarf_Endianness get_byte_order(void *const obj)
{
    return DW_OBJECT_LSB;
}

static Dwarf_Small get_length_size(void *const obj)
{
    return sizeof (uint32_t);
}

static Dwarf_Small get_pointer_size(void *const obj)
{
    return sizeof (uint32_t);
}

static Dwarf_Unsigned get_section_count(void *const obj)
{
    const struct dwarf *const dw = obj;
    Dwarf_Unsigned ret = 0;

    for (size_t i = 0; i < sizeof dw->sections / sizeof *dw->sections; i++)
        if (dw->sections[i].offset)
            ret++;

    return ret;
}

static int load_section(void *const obj, const Dwarf_Half section_index,
    Dwarf_Small **const return_data, int *const error)
{
    struct dwarf *const dw = obj;
    FILE *const f = dw->f;
    Dwarf_Small *p = NULL;

    if (section_index >= NSECTIONS)
    {
        fprintf(stderr, "%s: invalid section_index %hd\n", __func__,
            section_index);
        goto failure;
    }

    struct dwsection *const s = &dw->sections[section_index];
    const char *const name = names[section_index];

    if (!s->offset)
    {
        fprintf(stderr, "%s: unavailable section: %s\n", __func__, name);
        goto failure;
    }
    else if (!s->len)
    {
        fprintf(stderr, "%s: unexpected zero length for section: %s\n",
            __func__, name);
        goto failure;
    }
    else if (!(p = malloc(s->len)))
    {
        fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
        goto failure;
    }
    else if (fseek(f, s->offset, SEEK_SET))
    {
        fprintf(stderr, "%s: fseek(3): %s\n", __func__, strerror(errno));
        goto failure;
    }
    else if (!fread(p, s->len, 1, f))
    {
        fprintf(stderr, "%s: fread(3) failed, feof=%d, ferror=%d\n", __func__,
            feof(f), ferror(f));
        goto failure;
    }

    s->data = p;
    *return_data = p;
    return DW_DLV_OK;

failure:
    free(p);
    return DW_DLV_ERROR;
}

static int check_header(FILE *const f)
{
    uint8_t magic[sizeof "asm"], version[sizeof (uint32_t)];
    static const uint8_t exp[sizeof version] = {1, 0, 0, 0};

    if (!fread(magic, sizeof magic, 1, f))
    {
        fprintf(stderr, "%s: fread(3) magic failed, feof=%d, ferror=%d\n",
            __func__, feof(f), ferror(f));
        return -1;
    }
    else if (memcmp(magic, "\0asm", sizeof magic))
    {
        fprintf(stderr, "%s: invalid magic number\n", __func__);
        return -1;
    }
    else if (!fread(version, sizeof version, 1, f))
    {
        fprintf(stderr, "%s: fread(3) version failed, feof=%d, ferror=%d\n",
            __func__, feof(f), ferror(f));
        return -1;
    }
    else if (memcmp(version, exp, sizeof version))
    {
        fprintf(stderr, "%s: invalid version number\n", __func__);
        return -1;
    }

    return 0;
}

static char *read_name(FILE *const f)
{
    varuint32 name_len;
    char *name = malloc(1);

    if (!name)
    {
        fprintf(stderr, "%s: malloc(3): %s\n", __func__, strerror(errno));
        goto failure;
    }
    else if (read_varuint32(f, &name_len))
    {
        fprintf(stderr, "%s: read_varuint32 failed\n", __func__);
        goto failure;
    }

    for (varuint32 i = 0; i < name_len; i++)
    {
        uint8_t c;
        const size_t r = fread(&c, sizeof c, 1, f);

        if (!r)
        {
            fprintf(stderr, "%s: fread(3) failed, ferror(3)=%d, feof(3)=%d\n",
                __func__, ferror(f), feof(f));
            goto failure;
        }

        char *const newname = realloc(name, i + 2);

        if (!newname)
        {
            fprintf(stderr, "%s: realloc(3): %s\n", __func__, strerror(errno));
            goto failure;
        }

        name = newname;
        name[i] = c;
    }

    name[name_len] = '\0';
    return name;

failure:
    free(name);
    return NULL;
}

struct section
{
    varuint7 code;
    varuint32 len;
    char *name;
};

static int parse_header(FILE *const f, struct section *const s)
{
    varuint7 code;
    varuint32 payload_len;
    char *name = NULL;
    long before, after;

    if (read_varuint7(f, &code))
    {
        /* Exceptionally, this might not be a fatal error. */
        if (!feof(f))
            fprintf(stderr, "%s: read_varuint7 failed\n", __func__);

        goto failure;
    }
    else if (read_varuint32(f, &payload_len))
    {
        fprintf(stderr, "%s: read_varuint32 failed\n", __func__);
        goto failure;
    }
    else if ((before = ftell(f)) < 0)
    {
        fprintf(stderr, "%s: ftell(3) before: %s\n", __func__, strerror(errno));
        goto failure;
    }
    else if (!code && !(name = read_name(f)))
    {
        fprintf(stderr, "%s: read_name failed\n", __func__);
        goto failure;
    }
    else if ((after = ftell(f)) < 0)
    {
        fprintf(stderr, "%s: ftell(3) after: %s\n", __func__, strerror(errno));
        goto failure;
    }

    const unsigned long sz = after - before;

    if (payload_len < sz)
    {
        fprintf(stderr, "%s: expected payload_len >= %lu, got %lu\n",
            __func__, sz, (unsigned long)payload_len);
        goto failure;
    }

    payload_len -= sz;

    *s = (const struct section)
    {
        .code = code,
        .len = payload_len,
        .name = name
    };

    return 0;

failure:
    free(name);
    return -1;
}

static int skip(FILE *const f, const struct section *const s)
{
    const int ret = fseek(f, s->len, SEEK_CUR);

    if (ret)
        fprintf(stderr, "%s: fseek(3): %s\n", __func__, strerror(errno));

    return ret;
}

static struct dwsection *getdws(struct dwarf *const dw,
    const char *const name)
{
    for (size_t i = 0; i < sizeof names / sizeof *names; i++)
        if (!strcmp(name, names[i]))
            return &dw->sections[i];

    return NULL;
}

static int read_section(FILE *const f, struct dwarf *const dw)
{
    int ret = -1;
    struct section s = {0};
    struct dwsection *dws;
    long offset;

    if (parse_header(f, &s))
    {
        /* Exceptionally, this might not be a fatal error. */
        if (!feof(f))
            fprintf(stderr, "%s: parse_header failed\n", __func__);

        goto end;
    }
    else if (s.code != SECTION_CUSTOM || !(dws = getdws(dw, s.name)))
    {
        if (skip(f, &s))
        {
            fprintf(stderr, "%s: skip failed\n", __func__);
            goto end;
        }
    }
    else if ((offset = ftell(f)) < 0)
    {
        fprintf(stderr, "%s: ftell(3): %s\n", __func__, strerror(errno));
        goto end;
    }
    else
    {
        *dws = (const struct dwsection)
        {
            .len = s.len,
            .offset = offset
        };

        if (skip(f, &s))
        {
            fprintf(stderr, "%s: skip failed\n", __func__);
            goto end;
        }
    }

    ret = 0;

end:
    free(s.name);
    return ret;
}

static int parse(struct dwarf *const dw)
{
    FILE *const f = dw->f;

    if (check_header(f))
    {
        fprintf(stderr, "%s: check_magic failed\n", __func__);
        return -1;
    }

    for (;;)
        if (read_section(f, dw))
        {
            if (feof(f))
                break;

            fprintf(stderr, "%s: read_section failed\n", __func__);
            return -1;
        }

    return 0;
}

static bool
isformstring(const Dwarf_Half form)
{
    switch (form)
    {
        case DW_FORM_string:
        case DW_FORM_GNU_strp_alt:
        case DW_FORM_GNU_str_index:
        case DW_FORM_strx:
        case DW_FORM_strx1:
        case DW_FORM_strx2:
        case DW_FORM_strx3:
        case DW_FORM_strx4:
        case DW_FORM_strp:
            return true;

        default:
            break;
    }

    return false;
}

static int read_attr(const Dwarf_Attribute a, const unsigned level,
    Dwarf_Error *const e)
{
    Dwarf_Half num, form;
    const char *atname, *fname;
    char *s = NULL;
    int res = dwarf_whatattr(a, &num, e);

    if (res)
    {
        fprintf(stderr, "%s: dwarf_whatattr failed with %d\n", __func__, res);
        return -1;
    }
    else if ((res = dwarf_whatform(a, &form, e)))
    {
        fprintf(stderr, "%s: dwarf_whatform failed with %d\n", __func__, res);
        return -1;
    }
    else if ((res = dwarf_get_AT_name(num, &atname)))
    {
        fprintf(stderr, "%s: dwarf_get_AT_name failed with %d\n", __func__,
            res);
        return -1;
    }
    else if ((res = dwarf_get_FORM_name(form, &fname)))
    {
        fprintf(stderr, "%s: dwarf_get_FORM_name failed with %d\n", __func__,
            res);
        return -1;
    }
    else if (isformstring(form) && (res = dwarf_formstring(a, &s, e)))
    {
        fprintf(stderr, "%s: dwarf_formstring failed with %d\n", __func__, res);
        return -1;
    }

#if 0
    for (unsigned i = 0; i < level; i++)
        putchar('\t');

    printf("atname=%s, fname=%s", atname, fname);

    if (s)
        printf(", s=%s", s);

    putchar('\n');
#endif

    return 0;
}

static int print_die(const Dwarf_Debug dbg, const Dwarf_Die die,
    const unsigned level, Dwarf_Error *const e)
{
    Dwarf_Half tag;
    Dwarf_Attribute *attrs = NULL;
    Dwarf_Signed nattr = 0;
    const char *name;
    int ret = -1, r = dwarf_tag(die, &tag, e);

    if (r)
    {
        fprintf(stderr, "%s: dwarf_tag failed with %d\n", __func__, r);
        goto end;
    }
    else if ((r = dwarf_get_TAG_name(tag, &name)))
        name = "<bogus tag>";

    if ((r = dwarf_attrlist(die, &attrs, &nattr, e)))
    {
        fprintf(stderr, "%s: dwarf_attrlist failed with %d\n", __func__, r);
        goto end;
    }

    for (Dwarf_Signed i = 0; i < nattr; i++)
        if (read_attr(attrs[i], level, e))
        {
            fprintf(stderr, "%s: failed to read attribute %lld\n", __func__, i);
            goto end;
        }

    ret = 0;

end:

    for (Dwarf_Signed i = 0; i < nattr; i++)
        dwarf_dealloc_attribute(attrs[i]);

    dwarf_dealloc(dbg, attrs, DW_DLA_LIST);
    return ret;
}

static int read_children(const Dwarf_Debug dbg, const Dwarf_Die die,
    const unsigned level, Dwarf_Error *const e)
{
    int ret = -1;
    Dwarf_Die child;
    int r;

    if (print_die(dbg, die, level, e))
    {
        fprintf(stderr, "%s: failed to print die\n", __func__);
        return -1;
    }
    else if (!(r = dwarf_child(die, &child, e)))
    {
        ret = read_children(dbg, child, level + 1, e);
        dwarf_dealloc_die(child);
        return ret;
    }
    else if (r == DW_DLV_ERROR)
    {
        fprintf(stderr, "%s: dwarf_child failed\n", __func__);
        return -1;
    }

    Dwarf_Die d = die;

    for (;;)
    {
        Dwarf_Die sibling;

        if (!(r = dwarf_siblingof(dbg, d, &sibling, e)))
        {
            ret = read_children(dbg, sibling, level, e);

            if (ret)
                return ret;
        }
        else if (r == DW_DLV_ERROR)
        {
            fprintf(stderr, "%s: dwarf_siblingof failed\n", __func__);
            return -1;
        }
        else if (r == DW_DLV_NO_ENTRY)
            break;

        d = sibling;
    }

    return 0;
}

static int read_header(const Dwarf_Debug dbg, struct header *const h,
    Dwarf_Error *const e)
{
    Dwarf_Die die = 0;
    int ret = -1, r = dwarf_next_cu_header_d(dbg, 1, &h->cu_header_length,
        &h->version_stamp, &h->abbrev_offset, &h->address_size,
        &h->length_size, &h->extension_size, &h->type_signature,
        &h->typeoffset, &h->next_cu_header_offset, &h->header_cu_type, e);

    if (r != DW_DLV_OK)
    {
        fprintf(stderr, "%s: dwarf_next_cu_header_d failed with %d\n",
            __func__, r);
        return -1;
    }
    else if ((r = dwarf_siblingof(dbg, NULL, &die, e)))
    {
        fprintf(stderr, "%s: dwarf_siblingof failed with %d\n", __func__, r);
        goto end;
    }
    else if (read_children(dbg, die, 0, e))
    {
        fprintf(stderr, "%s: failed to read children\n", __func__);
        goto end;
    }

    ret = 0;

end:
    dwarf_dealloc_die(die);
    return ret;
}

static int init_client(const char *const tgt)
{
    int ret = -1, fd = -1;
    char *hostdup = NULL, *portdup = NULL;
    const char *sep = strchr(tgt, ':'), *host, *port;
    struct addrinfo *pai = NULL;
    unsigned long portv;

    if (!sep)
    {
        host = tgt;
        port = "3333";
    }
    else
    {
        if (!*(sep + 1))
        {
            fprintf(stderr, "%s: missing port number\n", __func__);
            goto end;
        }
        else if (sep == tgt)
            host = "localhost";
        else if (!(hostdup = strndup(tgt, sep - tgt)))
        {
            perror("strndup(3)");
            goto end;
        }
        else
            host = hostdup;

        if (!(portdup = strdup(sep + 1)))
        {
            fprintf(stderr, "%s: failed to duplicate string: %s\n", __func__,
                strerror(errno));
            goto end;
        }
        else
            port = portdup;
    }

    char *end;
    int error;
    const struct addrinfo ai =
    {
        .ai_family = AF_INET,
        .ai_socktype = SOCK_STREAM
    };

    errno = 0;
    portv = strtoul(port, &end, 10);

    if (errno || *end || portv > USHRT_MAX)
    {
        fprintf(stderr, "%s: invalid port number: %s\n", __func__, port);
        goto end;
    }
    else if ((error = getaddrinfo(host, port, &ai, &pai)))
    {
        fprintf(stderr, "%s: getaddrinfo(3) %s:%s: %s\n", __func__,
            host, port, gai_strerror(error));
        goto end;
    }

    for (const struct addrinfo *a = pai; a; a = a->ai_next)
    {
        if ((fd = socket(a->ai_family, a->ai_socktype, a->ai_protocol)) < 0)
        {
            perror("socket(2)");
            continue;
        }
        else if (connect(fd, a->ai_addr, a->ai_addrlen))
        {
            fprintf(stderr, "%s: connect(2) %s:%s: %s\n", __func__,
                host, port, strerror(errno));
            goto end;
        }

        break;
    }

    ret = fd;

end:

    if (ret < 0 && fd >= 0 && close(fd))
        perror("close(2)");

    if (pai)
        freeaddrinfo(pai);

    free(hostdup);
    free(portdup);
    return ret;
}

struct verb
{
    const char *verb;
    int (*f)(void);
};

static int help(void);

static const struct verb verbs[] =
{
    {"?", help},
    {"help", help}
};

static int help(void)
{
    return -1;
}

static int process(const char *const l)
{
    return 0;
}

static int run(const int fd)
{
    int ret = -1;
    char *l;
    size_t n = 0;
    ssize_t r;

    printf("(wadb) ");
    fflush(stdout);

    if ((r = getline(&l, &n, stdin) < 0))
    {
        if (feof(stdin))
        {
            putchar('\n');
            return 1;
        }
        else
            perror("getline(3)");

        goto end;
    }

    *strchr(l, '\n') = '\0';

    if (process(l))
        goto end;

    ret = 0;

end:
    free(l);
    return ret;
}

int main(int argc, char *argv[])
{
    static const Dwarf_Obj_Access_Methods methods =
    {
        .get_section_info = get_section_info,
        .get_byte_order = get_byte_order,
        .get_length_size = get_length_size,
        .get_pointer_size = get_pointer_size,
        .get_section_count = get_section_count,
        .load_section = load_section
    };

    int ret = EXIT_FAILURE, result, fd = -1;
    struct dwarf dw = {0};
    Dwarf_Obj_Access_Interface aitf = {.object = &dw, .methods = &methods};
    Dwarf_Debug dbg = 0;
    Dwarf_Error error = 0;
    struct header h;

    if (argc < 2)
    {
        fprintf(stderr, "%s [-h <host:port>] <wasm-file> [args ...]\n", *argv);
        goto end;
    }

    const char *hostport = "localhost:3333";
    int opt;

    while ((opt = getopt(argc, argv, "h:")) != -1)
        switch (opt)
        {
            case 'h':
                hostport = optarg;
                break;
        }

    const char *const path = argv[optind];

    if (!(dw.f = fopen(path, "rb")))
    {
        fprintf(stderr, "fopen(3) %s: %s\n", path, strerror(errno));
        goto end;
    }
    else if (parse(&dw))
    {
        fprintf(stderr, "failed to parse %s\n", path);
        goto end;
    }
    else if ((result = dwarf_object_init(&aitf, errcb, &dw, &dbg, &error))
        != DW_DLV_OK)
    {
        fprintf(stderr, "dwarf_object_init failed with %d: %s\n", result,
            dwarf_errmsg(error));
        goto end;
    }
    else if (read_header(dbg, &h, &error))
    {
        fprintf(stderr, "failed to read header\n");
        goto end;
    }
    else if ((fd = init_client(hostport)) < 0)
    {
        fprintf(stderr, "failed to init client\n");
        goto end;
    }

    while (!(result = run(fd)))
        ;

    if (result < 0)
        goto end;

    ret = EXIT_SUCCESS;

end:

    if (fd >= 0 && close(fd))
    {
        perror("close(2)");
        ret = EXIT_FAILURE;
    }

    for (size_t i = 0; i < sizeof dw.sections / sizeof *dw.sections; i++)
        free(dw.sections[i].data);

    if (dbg && dwarf_object_finish(dbg, &error))
    {
        fprintf(stderr, "dwarf_object_finish: %s\n", dwarf_errmsg(error));
        ret = EXIT_FAILURE;
    }

    if (dw.f && fclose(dw.f))
    {
        fprintf(stderr, "fclose(3) %s: %s\n", path, strerror(errno));
        ret = EXIT_FAILURE;
    }

    return ret;
}