/*
 * db.c - package database
 * https://rawnix.org
 *
 * Copyright (c) 2025 zorz@gmx.com
 * SPDX-License-Identifier: BSD-2-Clause
 *
 * Database format (plain text, records separated by blank lines):
 *   <name>\n
 *   <version>\n
 *   <file1>\n      relative paths, no leading /
 *   <file2>\n
 *   \n
 */

#include "db.h"

#include <err.h>
#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/file.h>
#include <sys/stat.h>

static char *get_dbdir(const char *root)
{
    const char *env = getenv("PKG_DBDIR");

    /* if env is set and absolute, use it directly — don't join with root */
    if (env && env[0] == '/')
        return xstrdup(env);

    return path_join(root, env && env[0] ? env : PKG_DBDIR);
}

pkg_t *pkg_new(const char *name, const char *version)
{
    pkg_t *p = xmalloc(sizeof(pkg_t));
    p->name    = xstrdup(name);
    p->version = xstrdup(version);
    p->files   = strarray_new();
    p->next    = NULL;
    return p;
}

void pkg_free(pkg_t *p)
{
    if (!p)
        return;
    free(p->name);
    free(p->version);
    strarray_free(p->files);
    free(p);
}

pkgdb_t *db_open(const char *root, int exclusive)
{
    pkgdb_t *db;
    char    *dbfile;
    FILE    *fp;
    char    *line = NULL;
    size_t   len  = 0;
    ssize_t  n;
    pkg_t   *pkg  = NULL;
    enum { DB_NAME, DB_VERSION, DB_FILES } state = DB_NAME;

    db          = xmalloc(sizeof(pkgdb_t));
    db->head    = NULL;
    db->root    = xstrdup(root ? root : "/");
    db->dbdir   = get_dbdir(db->root);
    db->fd      = -1;

    if (mkdirp(db->dbdir, 0755) < 0)
        err(1, "cannot create %s", db->dbdir);

    db->fd = open(db->dbdir, O_RDONLY | O_DIRECTORY);
    if (db->fd < 0)
        err(1, "cannot open %s", db->dbdir);

    if (flock(db->fd, (exclusive ? LOCK_EX : LOCK_SH) | LOCK_NB) < 0) {
        if (errno == EWOULDBLOCK)
            errx(1, "package database is locked by another process");
        err(1, "cannot lock %s", db->dbdir);
    }

    dbfile = path_join(db->dbdir, PKG_DBFILE);
    fp     = fopen(dbfile, "r");
    free(dbfile);

    if (!fp) {
        if (errno == ENOENT)
            return db;
        err(1, "cannot open database");
    }

    while ((n = getline(&line, &len, fp)) != -1) {
        if (n > 0 && line[n - 1] == '\n')
            line[--n] = '\0';

        if (n == 0) {
            if (pkg) {
                pkg->next = db->head;
                db->head  = pkg;
                pkg       = NULL;
            }
            state = DB_NAME;
        } else if (state == DB_NAME) {
            pkg   = pkg_new(line, "");
            state = DB_VERSION;
        } else if (state == DB_VERSION) {
            free(pkg->version);
            pkg->version = xstrdup(line);
            state        = DB_FILES;
        } else {
            strarray_add(pkg->files, line);
        }
    }

    /* handle last record if file has no trailing newline */
    if (pkg) {
        pkg->next = db->head;
        db->head  = pkg;
    }

    if (ferror(fp))
        err(1, "error reading database");

    free(line);
    fclose(fp);
    return db;
}

void db_close(pkgdb_t *db)
{
    pkg_t *p, *next;

    if (!db)
        return;

    for (p = db->head; p; p = next) {
        next = p->next;
        pkg_free(p);
    }

    if (db->fd >= 0) {
        flock(db->fd, LOCK_UN);
        close(db->fd);
    }

    free(db->root);
    free(db->dbdir);
    free(db);
}

int db_write(pkgdb_t *db)
{
    char   *dbfile, *tmpfile;
    FILE   *fp;
    pkg_t  *p;
    size_t  i;
    int     fd;

    dbfile  = path_join(db->dbdir, PKG_DBFILE);
    tmpfile = path_join(db->dbdir, PKG_DBFILE ".tmp");

    fd = open(tmpfile, O_WRONLY | O_CREAT | O_TRUNC, 0644);
    if (fd < 0) {
        warn("cannot create %s", tmpfile);
        free(dbfile);
        free(tmpfile);
        return -1;
    }

    fp = fdopen(fd, "w");
    if (!fp) {
        close(fd);
        free(dbfile);
        free(tmpfile);
        return -1;
    }

    for (p = db->head; p; p = p->next) {
        if (p->files->count == 0)
            continue;
        fprintf(fp, "%s\n%s\n", p->name, p->version);
        strarray_sort(p->files);
        for (i = 0; i < p->files->count; i++)
            fprintf(fp, "%s\n", p->files->items[i]);
        fputc('\n', fp);
    }

    if (fflush(fp) != 0 || ferror(fp)) {
        warn("write error on %s", tmpfile);
        fclose(fp);
        unlink(tmpfile);
        free(dbfile);
        free(tmpfile);
        return -1;
    }

    fsync(fd);
    fclose(fp);

    if (rename(tmpfile, dbfile) < 0) {
        warn("cannot rename %s to %s", tmpfile, dbfile);
        unlink(tmpfile);
        free(dbfile);
        free(tmpfile);
        return -1;
    }

    /* fsync the directory to make the rename durable */
    {
        int dfd = open(db->dbdir, O_RDONLY | O_DIRECTORY);
        if (dfd >= 0) {
            fsync(dfd);
            close(dfd);
        }
    }

    free(dbfile);
    free(tmpfile);
    return 0;
}

pkg_t *db_find(pkgdb_t *db, const char *name)
{
    pkg_t *p;
    for (p = db->head; p; p = p->next)
        if (strcmp(p->name, name) == 0)
            return p;
    return NULL;
}

int db_add(pkgdb_t *db, pkg_t *p)
{
    pkg_t *cur;

    /*
     * Guard against the caller passing a pkg pointer that's already
     * in the list.  db_remove(by name) would free `p` itself, leaving
     * us linking freed memory.  Today's callers always pass a fresh
     * pkg_new() result, but the check is cheap and defensive.
     */
    for (cur = db->head; cur; cur = cur->next) {
        if (cur == p)
            return 0;   /* already in list */
    }

    db_remove(db, p->name);
    p->next  = db->head;
    db->head = p;
    return 0;
}

int db_remove(pkgdb_t *db, const char *name)
{
    pkg_t *p, *prev = NULL;

    for (p = db->head; p; prev = p, p = p->next) {
        if (strcmp(p->name, name) == 0) {
            if (prev)
                prev->next = p->next;
            else
                db->head = p->next;
            pkg_free(p);
            return 0;
        }
    }
    return -1;
}