/*                 _,.---._    .-._        .--.-. ,--.--------.
 *   _,..---._   ,-.' , -  `. /==/ \  .-._/==/  //==/,  -   , -\
 * /==/,   -  \ /==/_,  ,  - \|==|, \/ /, |==\ -\\==\.-.  - ,-./
 * |==|   _   _\==|   .=.     |==|-  \|  | \==\- \`--`\==\- \
 * |==|  .=.   |==|_ : ;=:  - |==| ,  | -|  `--`-'     \==\_ \
 * |==|,|   | -|==| , '='     |==| -   _ |             |==|- |
 * |==|  '='   /\==\ -    ,_ /|==|  /\ , |             |==|, |
 * |==|-,   _`/  '.='. -   .' /==/, | |- |             /==/ -/
 * `-.`.____.'     `--`--''   `--`./  `--`             `--`--`
 *                    _ __    ,---.      .-._         .=-.-.  _,.----.
 *                 .-`.' ,`..--.'  \    /==/ \  .-._ /==/_ /.' .' -   \
 *                /==/, -   \==\-/\ \   |==|, \/ /, /==|, |/==/  ,  ,-'
 *               |==| _ .=. /==/-|_\ |  |==|-  \|  ||==|  ||==|-   |  .
 *               |==| , '=',\==\,   - \ |==| ,  | -||==|- ||==|_   `-' \
 *               |==|-  '..'/==/ -   ,| |==| -   _ ||==| ,||==|   _  , |
 *               |==|,  |  /==/-  /\ - \|==|  /\ , ||==|- |\==\.       /
 *               /==/ - |  \==\ _.\=\.-'/==/, | |- |/==/. / `-.`.___.-'
 *               `--`---'   `--`        `--`./  `--``--`-`
 *
 *	@(#)Copyright (c) 2023, Nathan D. Fisher.
 *
 *      This is free software.  It comes with NO WARRANTY.
 *      Permission to use, modify and distribute this source code
 *      is granted subject to the following conditions.
 *      1/ that the above copyright notice and this notice
 *      are preserved in all copies and that due credit be given
 *      to the author.
 *      2/ that any changes to this code are clearly commented
 *      as such so that the author does not get blamed for bugs
 *      other than his own.
 */

#include <limits.h>          // PATH_MAX
#include <stddef.h>
#include <stdint.h>          // uint<x>_t

#if defined(__FreeBSD__) || defined(__DragonFly__)
#include <sha.h>
#include <sha256.h>
#include <sys/types.h>
#elif defined(__NetBSD__) || defined(__OpenBSD__)
#include <sha1.h>
#include <sha2.h>
#include <sys/types.h>
#elif defined(__linux__)
#include <sha1.h>
#include <sha2.h>
#include <sys/sysmacros.h>   // major, minor, dev_t
#endif /* if defined (__FreeBSD__) */
#include <md5.h>

#include <stdio.h>           // fopen, fread, fwrite, FILE
#include <stdlib.h>          // free, malloc
#include <string.h>          // memcpy, strlen
#include <unistd.h>          // readlink
#include <sys/stat.h>        // stat

#include "bytes.h"
#include "haggis.h"
#include "linklist.h"

static unsigned char header[7] = {0x89, 'h', 'a', 'g', 'g', 'i', 's'};

int haggis_store_header(FILE *stream) {
    if (fwrite(header, 1, 7, stream) < 7)
        return 1;
    return 0;
}

int haggis_check_header(FILE *stream) {
    unsigned char *buf[7];
    if (fread(buf, 1, 7, stream) < 7)
        return 1;
    if (memcmp(buf, header, 7))
        return 2;
    return 0;
}

void haggis_device_init(dev_t rdev, haggis_device *dev) {
    dev->major.val = (uint32_t)major(rdev);
    dev->minor.val = (uint32_t)minor(rdev);
}

int haggis_store_device(FILE *stream, haggis_device *dev) {
    if (fwrite(dev->major.bytes, 1, 4, stream) != 4)
        return 1;
    if (fwrite(dev->minor.bytes, 1, 4, stream) != 4)
        return 1;
    return 0;
}

int haggis_load_device(FILE *stream, haggis_device *dev) {
    if (fread(dev->major.bytes, 1, 4, stream) != 4)
        return 1;
    if (fread(dev->minor.bytes, 1, 4, stream) != 4)
        return 1;
    return 0;
}

int haggis_store_cksum(FILE *stream, haggis_checksum *cksum) {
    u8 flag;

    switch (cksum->tag) {
    case md5:
        flag = 0;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        if (fwrite(cksum->sum.md5, 1, 16, stream) != 16)
            return 1;
        break;
    case sha1:
        flag = 1;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        if (fwrite(cksum->sum.sha1, 1, 20, stream) != 20)
            return 1;
        break;
    case sha256:
        flag = 2;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        if (fwrite(cksum->sum.sha256, 1, 32, stream) != 32)
            return 1;
        break;
    case skip:
        flag = 3;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        break;
    }
    return 0;
}

int haggis_load_cksum(FILE *stream, haggis_checksum *cksum) {
    u8 flag;

    if (fread(&flag, 1, 1, stream) != 1)
        return 1;
    switch (flag) {
    case md5:
        cksum->tag = 0;
        if (fread(&cksum->sum.md5, 1, 16, stream) != 16)
            return 1;
        break;
    case sha1:
        cksum->tag = 1;
        if (fread(&cksum->sum.sha1, 1, 20, stream) != 20)
            return 1;
        break;
    case sha256:
        cksum->tag = 2;
        if (fread(&cksum->sum.sha256, 1, 32, stream) != 32)
            return 1;
        break;
    case skip:
        cksum->tag = 3;
        break;
    }
    return 0;
}

void init_md5(haggis_file *f) {
    MD5_CTX ctx;

    f->cksum.tag = md5;
    MD5Init(&ctx);
    MD5Update(&ctx, f->data, (size_t)f->len.val);
    MD5Final(f->cksum.sum.md5, &ctx);
}

int validate_md5(haggis_file *file) {
    MD5_CTX ctx;
    u8 digest[16];

    MD5Init(&ctx);
    MD5Update(&ctx, file->data, (size_t)file->len.val);
    MD5Final(digest, &ctx);
    if (memcmp(file->cksum.sum.md5, digest, sizeof(digest)))
        return 2;
    return 0;
}

#if defined(__FreeBSD__) || defined(__DragonFly__)
void init_sha1(haggis_file *f) {
    SHA1_CTX ctx;

    f->cksum.tag = sha1;
    SHA1_Init(&ctx);
    SHA1_Update(&ctx, f->data, (size_t)f->len.val);
    SHA1_Final(f->cksum.sum.sha1, &ctx);
}

int validate_sha1(haggis_file *file) {
    SHA1_CTX ctx;
    u8 digest[20];

    SHA1_Init(&ctx);
    SHA1_Update(&ctx, file->data, (size_t)file->len.val);
    SHA1_Final(digest, &ctx);
    if (memcmp(file->cksum.sum.sha1, digest, sizeof(digest)))
        return 2;
    return 0;
}
#elif defined(__linux__) || defined(__NetBSD__) || defined(__OpenBSD__)
void init_sha1(haggis_file *f) {
    SHA1_CTX ctx;

    f->cksum.tag = sha1;
    SHA1_Init(&ctx);
    SHA1_Update(&ctx, f->data, (size_t)f->len.val);
    SHA1_Final(f->cksum.sum.sha1, &ctx);
}

int validate_sha1(haggis_file *file) {
    SHA1_CTX ctx;
    u8 digest[20];

    SHA1Init(&ctx);
    SHA1Update(&ctx, file->data, (size_t)file->len.val);
    SHA1Final(digest, &ctx);
    if (memcmp(file->cksum.sum.sha1, digest, sizeof(digest)))
        return 2;
    return 0;
}
#endif /* if defined (__FreeBSD__) */

#if defined(__FreeBSD__) || defined(__DragonFly) || defined(__NetBSD__)
void init_sha256(haggis_file *f) {
    SHA256_CTX ctx;

    f->cksum.tag = sha256;
    SHA256_Init(&ctx);
    SHA256_Update(&ctx, f->data, (size_t)f->len.val);
    SHA256_Final(f->cksum.sum.sha256, &ctx);
}

int validate_sha256(haggis_file *file) {
    SHA256_CTX ctx;
    u8 digest[32];

    SHA256_Init(&ctx);
    SHA256_Update(&ctx, file->data, (size_t)file->len.val);
    SHA256_Final(digest, &ctx);
    if (memcmp(file->cksum.sum.sha256, digest, sizeof(digest)))
        return 2;
    return 0;
}
#elif defined(__linux__) || defined(__OpenBSD__)
void init_sha256(haggis_file *f) {
    SHA2_CTX ctx;

    f->cksum.tag = sha256;
    SHA256_Init(&ctx);
    SHA256_Update(&ctx, f->data, (size_t)f->len.val);
    SHA256_Final(f->cksum.sum.sha256, &ctx);
}

int validate_sha256(haggis_file *file) {
    SHA2_CTX ctx;
    u8 digest[32];

    SHA256Init(&ctx);
    SHA256Update(&ctx, file->data, (size_t)file->len.val);
    SHA256Final(digest, &ctx);
    if (memcmp(file->cksum.sum.sha256, digest, sizeof(digest)))
        return 2;
    return 0;
}
#endif /* if defined (__FreeBSD__) */

void haggis_init_cksum(haggis_file *f, haggis_algorithm a) {
    switch (a) {
    case md5:
        init_md5(f);
        break;
    case sha1:
        init_sha1(f);
        break;
    case sha256:
        init_sha256(f);
        break;
    case skip:
        break;
    }
}

int haggis_validate_cksum(haggis_file *file) {
    switch (file->cksum.tag) {
    case md5:
        return validate_md5(file);
    case sha1:
        return validate_sha1(file);
    case sha256:
        return validate_sha256(file);
    case skip:
        return 0;
    }
    return 0;
}

int haggis_file_init(char *path, haggis_file *hf, haggis_algorithm a) {
    FILE *f;
    long len;

    f = fopen(path, "r");
    if (f == NULL) return 2;
    if (fseek(f, 0, SEEK_END) == -1) {
        fclose(f);
        return 2;
    }
    len = ftell(f);
    if (len == -1) {
        fclose(f);
        return 2;
    }
    hf->len.val = (uint64_t)len;
    rewind(f);
    hf->data = malloc((size_t)len);
    if (fread(hf->data, 1, (size_t)len, f) != (size_t)len) {
        free(hf->data);
        fclose(f);
        return 1;
    }
    fclose(f);
    haggis_init_cksum(hf, a);
    return 0;
}

void haggis_file_deinit(haggis_file *f) {
    if (f->data != NULL) free(f->data);
}

int haggis_store_file(FILE *stream, haggis_file *file) {
    if (store_u64(stream, file->len) != 8)
        return 1;
    if (haggis_store_cksum(stream, &file->cksum) != 0)
        return 1;
    int res = fwrite(file->data, 1, (size_t)file->len.val, stream);
    if (res != (size_t)file->len.val)
        return 1;
    return 0;
}

int haggis_load_file(FILE *stream, haggis_file *f) {
    if (load_u64(stream, f->len) != 8)
        return 1;
    if (haggis_load_cksum(stream, &f->cksum) != 0)
        return 1;
    f->data = malloc((size_t)f->len.val);
    if (f->data == NULL)
        return -1;
    int res = fread(f->data, 1, (size_t)f->len.val, stream);
    if (res != (size_t)f->len.val) {
        free(f->data);
        return 1;
    }
    if (haggis_validate_cksum(f)) {
        free(f->data);
        return 1;
    }
    return 0;
}

void haggis_filename_init(char *target, haggis_filename *fname) {
    size_t len;

    len = strlen(target) - 1;
    fname->len.val = (uint16_t)len;
    fname->name = target;
}

void haggis_filename_deinit(haggis_filename *fname) {
    if (fname->name != NULL) free(fname->name);
}

int haggis_load_filename(FILE *stream, haggis_filename *n) {
    u16 len;
    char *name;

    len.val = 0;
    if (fread(len.bytes, 1, 2, stream) != 2) return 2;
    n->len = len;
    name = malloc((size_t)len.val);
    if (name == NULL) return -1;
    if (fread(name, 1, (size_t)len.val, stream) != (size_t)len.val) {
        free(name);
        return 2;
    }
    n->name = name;
    return 0;
}

int haggis_store_filename(FILE *stream, haggis_filename *n) {
    if (fwrite(n->len.bytes, 1, 2, stream) != 2) return 2;
    if (fwrite(n->name, 1, (size_t)n->len.val, stream) != (size_t)n->len.val)
        return 2;
    return 0;
}

int haggis_load_filetype(FILE *stream, haggis_typeflag tag, haggis_filetype *file) {
    switch (tag) {
    case normal:
        file->tag = 0;
        return haggis_load_file(stream, &file->f_type.file);
    case hardlink:
        return haggis_load_filename(stream, &file->f_type.target);
        file->tag = 1;
    case softlink:
        return haggis_load_filename(stream, &file->f_type.target);
        file->tag = 2;
    case directory:
        file->tag = 3;
        break;
    case character:
        file->tag = 4;
        return haggis_load_device(stream, &file->f_type.dev);
    case block:
        file->tag = 5;
        return haggis_load_device(stream, &file->f_type.dev);
    case fifo:
        file->tag = 6;
        break;
    case eof:
        file->tag = 7;
        break;
    }
    return 0;
}

int haggis_store_filetype(FILE *stream, haggis_filetype *filetype) {
    u8 flag;

    switch (filetype->tag) {
    case normal:
        flag = 0;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        if (haggis_store_file(stream, &filetype->f_type.file) != 0)
            return 1;
        break;
    case hardlink:
        flag = 1;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        return haggis_store_filename(stream, &filetype->f_type.target);
    case softlink:
        flag = 2;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        return haggis_store_filename(stream, &filetype->f_type.target);
    case directory:
        flag = 3;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        break;
    case character:
        flag = 4;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        if (haggis_store_device(stream, &filetype->f_type.dev) != 0)
            return 1;
        break;
    case block:
        flag = 5;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        if (haggis_store_device(stream, &filetype->f_type.dev) != 0)
            return 1;
        break;
    case fifo:
        flag = 6;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        break;
    case eof:
        flag = 7;
        if (fwrite(&flag, 1, 1, stream) != 1)
            return 1;
        break;
    };
    return 0;
}

haggis_typeflag haggis_filetype_from_mode(u16 mode) {
    u8 mask = 07 << 5;
    int filetype = (int)((mode.bytes[0] & mask) >> 5);
    return filetype;
}

u16 haggis_derive_mode(u16 raw, haggis_filetype *ft) {
    u16 mode;
    mode.val = ((uint16_t)ft->tag << 5) & raw.val;
    return mode;
}

void haggis_node_deinit(haggis_node *node) {
    if (node == NULL) return;
    if (node->name.name != NULL) haggis_filename_deinit(&node->name);
    switch (node->filetype.tag) {
        case normal:
            if (node->filetype.f_type.file.data != NULL) {
                free(node->filetype.f_type.file.data);
            }
            break;
        case hardlink:
        case softlink:
            if (node->filetype.f_type.target.name != NULL) {
                haggis_filename_deinit(&node->filetype.f_type.target);
            }
            break;
        case character:
        case block:
        case directory:
        case fifo:
        case eof:
            break;
    };
    free(node);
}

haggis_node* haggis_create_node(char *file, haggis_algorithm a, haggis_hardlink_list *list) {
    struct stat *st = NULL;
    u16 mode;
    char *target;
    char pathbuf[PATH_MAX];
    int res;
    haggis_node *node;

    node = malloc(sizeof(haggis_node));
    if (node == NULL) return NULL;
    if (stat(file, st) != 0) {
        free(node);
        return NULL;
    }
    if (S_ISBLK(st->st_mode)) {
        node->filetype.tag = block;
    } else if (S_ISCHR(st->st_mode)) {
        node->filetype.tag = character;
    } else if (S_ISDIR(st->st_mode)) {
        node->filetype.tag = directory;
    } else if (S_ISFIFO(st->st_mode)) {
        node->filetype.tag = fifo;
    } else if (S_ISLNK(st->st_mode)) {
        node->filetype.tag = softlink;
    } else if (S_ISREG(st->st_mode)) {
        node->filetype.tag = normal;
    } else {
        free(node);
        return NULL;
    }
    node->uid.val = (uint32_t)st->st_uid;
    node->gid.val = (uint32_t)st->st_gid;
    node->mtime.val = (uint64_t)st->st_mtim.tv_sec;
    mode.val = (uint16_t)(st->st_mode & 07777);
    node->mode = mode;
    switch (node->filetype.tag) {
        case normal:
            if (st->st_nlink > 1) {
                target = haggis_linklist_get_or_put(list, st->st_ino, file);
                if (target != NULL) {
                    node->filetype.tag = hardlink;
                    haggis_filename_init(target, &node->filetype.f_type.target);
                    return node;
                }
            }
            res = haggis_file_init(file, &node->filetype.f_type.file, a);
            if (res != 0) {
                haggis_node_deinit(node);
                return NULL;
            }
            break;
        case block:
            if (st->st_nlink > 1) {
                target = haggis_linklist_get_or_put(list, st->st_ino, file);
                if (target != NULL) {
                    node->filetype.tag = hardlink;
                    haggis_filename_init(target, &node->filetype.f_type.target);
                    return node;
                }
            }
            haggis_device_init(st->st_rdev, &node->filetype.f_type.dev);
            break;
        case character:
            if (st->st_nlink > 1) {
                target = haggis_linklist_get_or_put(list, st->st_ino, file);
                if (target != NULL) {
                    node->filetype.tag = hardlink;
                    haggis_filename_init(target, &node->filetype.f_type.target);
                    return node;
                }
            }
            haggis_device_init(st->st_rdev, &node->filetype.f_type.dev);
            break;
        case fifo:
            if (st->st_nlink > 1) {
                target = haggis_linklist_get_or_put(list, st->st_ino, file);
                if (target != NULL) {
                    node->filetype.tag = hardlink;
                    haggis_filename_init(target, &node->filetype.f_type.target);
                    return node;
                }
            }
            return node;
        case directory:
        case hardlink:
        case eof:
            return node;
        case softlink:
            node->filetype.tag = softlink;
            ssize_t res = readlink(file, pathbuf, PATH_MAX);
            if (res == -1) {
                haggis_node_deinit(node);
                return NULL;
            }
            target = malloc(res + 1);
            memcpy(target, pathbuf, (unsigned long)res);
            haggis_filename_init(target, &node->filetype.f_type.target);
            return node;
    }
    return node;
}

int haggis_extract_node(FILE *stram, haggis_node *node) {
    // todo
    return 0;
}

int haggis_load_node(FILE *stream, haggis_node *node) {
    int res;
    u16 mode;
    haggis_typeflag tag;

    mode.val = 0;
    res = haggis_load_filename(stream, &node->name);
    if (res)
        return res;
    res = load_u32(stream, node->uid);
    if (res != 4)
        return 2;
    res = load_u32(stream, node->gid);
    if (res != 4)
        return 2;
    res = load_u64(stream, node->mtime);
    if (res != 8)
        return 2;
    res = load_u16(stream, mode);
    if (res != 2)
        return 2;
    tag = haggis_filetype_from_mode(mode);
    node->mode.bytes[0] = mode.bytes[0] & 037;
    node->mode.bytes[1] = mode.bytes[1];
    res = haggis_load_filetype(stream, tag, &node->filetype);
    if (res)
        return res;
    return 0;
}

int haggis_store_node(FILE *stream, haggis_node *node) {
    u16 mode;

    if (haggis_store_filename(stream, &node->name) != (size_t)(node->name.len.val) + 2)
        return 2;
    if (store_u32(stream, node->uid) != 4) return 2;
    if (store_u32(stream, node->gid) != 4) return 2;
    if (store_u64(stream, node->mtime) != 8) return 2;
    mode = haggis_derive_mode(node->mode, &node->filetype);
    if (store_u16(stream, mode) != 2) return 2;
    return haggis_store_filetype(stream, &node->filetype);
}