#include <assert.h>
#include <errno.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include "qemu-queue.h"
#include "envlist.h"

struct envlist_entry {
        const char *ev_var;                     /* actual env value */
        QLIST_ENTRY(envlist_entry) ev_link;
};

struct envlist {
        QLIST_HEAD(, envlist_entry) el_entries; /* actual entries */
        size_t el_count;                        /* number of entries */
};

static int envlist_parse(envlist_t *envlist,
    const char *env, int (*)(envlist_t *, const char *));

/*
 * Allocates new envlist and returns pointer to that or
 * NULL in case of error.
 */
envlist_t *
envlist_create(void)
{
        envlist_t *envlist;

        if ((envlist = malloc(sizeof (*envlist))) == NULL)
                return (NULL);

        QLIST_INIT(&envlist->el_entries);
        envlist->el_count = 0;

        return (envlist);
}

/*
 * Releases given envlist and its entries.
 */
void
envlist_free(envlist_t *envlist)
{
        struct envlist_entry *entry;

        assert(envlist != NULL);

        while (envlist->el_entries.lh_first != NULL) {
                entry = envlist->el_entries.lh_first;
                QLIST_REMOVE(entry, ev_link);

                free((char *)entry->ev_var);
                free(entry);
        }
        free(envlist);
}

/*
 * Parses comma separated list of set/modify environment
 * variable entries and updates given enlist accordingly.
 *
 * For example:
 *     envlist_parse(el, "HOME=foo,SHELL=/bin/sh");
 *
 * inserts/sets environment variables HOME and SHELL.
 *
 * Returns 0 on success, errno otherwise.
 */
int
envlist_parse_set(envlist_t *envlist, const char *env)
{
        return (envlist_parse(envlist, env, &envlist_setenv));
}

/*
 * Parses comma separated list of unset environment variable
 * entries and removes given variables from given envlist.
 *
 * Returns 0 on success, errno otherwise.
 */
int
envlist_parse_unset(envlist_t *envlist, const char *env)
{
        return (envlist_parse(envlist, env, &envlist_unsetenv));
}

/*
 * Parses comma separated list of set, modify or unset entries
 * and calls given callback for each entry.
 *
 * Returns 0 in case of success, errno otherwise.
 */
static int
envlist_parse(envlist_t *envlist, const char *env,
    int (*callback)(envlist_t *, const char *))
{
        char *tmpenv, *envvar;
        char *envsave = NULL;

        assert(callback != NULL);

        if ((envlist == NULL) || (env == NULL))
                return (EINVAL);

        /*
         * We need to make temporary copy of the env string
         * as strtok_r(3) modifies it while it tokenizes.
         */
        if ((tmpenv = strdup(env)) == NULL)
                return (errno);

        envvar = strtok_r(tmpenv, ",", &envsave);
        while (envvar != NULL) {
                if ((*callback)(envlist, envvar) != 0) {
                        free(tmpenv);
                        return (errno);
                }
                envvar = strtok_r(NULL, ",", &envsave);
        }

        free(tmpenv);
        return (0);
}

/*
 * Sets environment value to envlist in similar manner
 * than putenv(3).
 *
 * Returns 0 in success, errno otherwise.
 */
int
envlist_setenv(envlist_t *envlist, const char *env)
{
        struct envlist_entry *entry = NULL;
        const char *eq_sign;
        size_t envname_len;

        if ((envlist == NULL) || (env == NULL))
                return (EINVAL);

        /* find out first equals sign in given env */
        if ((eq_sign = strchr(env, '=')) == NULL)
                return (EINVAL);
        envname_len = eq_sign - env + 1;

        /*
         * If there already exists variable with given name
         * we remove and release it before allocating a whole
         * new entry.
         */
        for (entry = envlist->el_entries.lh_first; entry != NULL;
            entry = entry->ev_link.le_next) {
                if (strncmp(entry->ev_var, env, envname_len) == 0)
                        break;
        }

        if (entry != NULL) {
                QLIST_REMOVE(entry, ev_link);
                free((char *)entry->ev_var);
                free(entry);
        } else {
                envlist->el_count++;
        }

        if ((entry = malloc(sizeof (*entry))) == NULL)
                return (errno);
        if ((entry->ev_var = strdup(env)) == NULL) {
                free(entry);
                return (errno);
        }
        QLIST_INSERT_HEAD(&envlist->el_entries, entry, ev_link);

        return (0);
}

/*
 * Removes given env value from envlist in similar manner
 * than unsetenv(3).  Returns 0 in success, errno otherwise.
 */
int
envlist_unsetenv(envlist_t *envlist, const char *env)
{
        struct envlist_entry *entry;
        size_t envname_len;

        if ((envlist == NULL) || (env == NULL))
                return (EINVAL);

        /* env is not allowed to contain '=' */
        if (strchr(env, '=') != NULL)
                return (EINVAL);

        /*
         * Find out the requested entry and remove
         * it from the list.
         */
        envname_len = strlen(env);
        for (entry = envlist->el_entries.lh_first; entry != NULL;
            entry = entry->ev_link.le_next) {
                if (strncmp(entry->ev_var, env, envname_len) == 0)
                        break;
        }
        if (entry != NULL) {
                QLIST_REMOVE(entry, ev_link);
                free((char *)entry->ev_var);
                free(entry);

                envlist->el_count--;
        }
        return (0);
}

/*
 * Returns given envlist as array of strings (in same form that
 * global variable environ is).  Caller must free returned memory
 * by calling free(3) for each element and for the array.  Returned
 * array and given envlist are not related (no common references).
 *
 * If caller provides count pointer, number of items in array is
 * stored there.  In case of error, NULL is returned and no memory
 * is allocated.
 */
char **
envlist_to_environ(const envlist_t *envlist, size_t *count)
{
        struct envlist_entry *entry;
        char **env, **penv;

        penv = env = malloc((envlist->el_count + 1) * sizeof (char *));
        if (env == NULL)
                return (NULL);

        for (entry = envlist->el_entries.lh_first; entry != NULL;
            entry = entry->ev_link.le_next) {
                *(penv++) = strdup(entry->ev_var);
        }
        *penv = NULL; /* NULL terminate the list */

        if (count != NULL)
                *count = envlist->el_count;

        return (env);
}