/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */

/*  Fluent Bit
 *  ==========
 *  Copyright (C) 2015-2022 The Fluent Bit Authors
 *
 *  Licensed under the Apache License, Version 2.0 (the "License");
 *  you may not use this file except in compliance with the License.
 *  You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 *  Unless required by applicable law or agreed to in writing, software
 *  distributed under the License is distributed on an "AS IS" BASIS,
 *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 *  See the License for the specific language governing permissions and
 *  limitations under the License.
 */

#include <fluent-bit/flb_info.h>
#include <fluent-bit/flb_hash_table.h>
#include <fluent-bit/flb_mem.h>
#include <fluent-bit/flb_log.h>
#include <fluent-bit/flb_str.h>
#include <fluent-bit/flb_env.h>

#include <stdlib.h>

static inline flb_sds_t buf_append(flb_sds_t buf, const char *str, int len)
{
    flb_sds_t tmp;

    tmp = flb_sds_cat(buf, str, len);
    if (!tmp) {
        return NULL;
    }

    return tmp;
}

/* Preset some useful variables */
static int env_preset(struct flb_env *env)
{
    int ret;
    char *buf;
    char tmp[512];

    /*
     * ${HOSTNAME} this variable is very useful to identify records,
     * despite this variable is recognized by the Shell, that does not
     * means that is exposed as a real environment variable, e.g:
     *
     *  1. $ echo $HOSTNAME
     *     monotop
     *  2. $ env | grep HOSTNAME
     *     (nothing)
     */
    buf = getenv("HOSTNAME");
    if (!buf) {
        ret = gethostname(tmp, sizeof(tmp) - 1);
        if (ret == 0) {
            flb_env_set(env, "HOSTNAME", tmp);
        }
    }

    return 0;
}

struct flb_env *flb_env_create()
{
    struct flb_env *env;
    struct flb_hash_table *ht;

    env = flb_malloc(sizeof(struct flb_env));
    if (!env) {
        flb_errno();
        return NULL;
    }

    /* Create the hash-table */
    ht = flb_hash_table_create(FLB_HASH_TABLE_EVICT_NONE, FLB_ENV_SIZE, -1);
    if (!ht) {
        flb_free(env);
        return NULL;
    }

    env->warn_unused = FLB_TRUE;
    env->ht = ht;
    env_preset(env);

    return env;
}

void flb_env_destroy(struct flb_env *env)
{
    flb_hash_table_destroy(env->ht);
    flb_free(env);
}

int flb_env_set(struct flb_env *env, const char *key, const char *val)
{
    int id;
    int klen;
    int vlen;
    void *out_buf;
    size_t out_size;

    /* Get lengths */
    klen = strlen(key);
    vlen = strlen(val);

    /* Check if the key is already set */
    id = flb_hash_table_get(env->ht, key, klen, &out_buf, &out_size);
    if (id >= 0) {
        /* Remove the old entry */
        flb_hash_table_del(env->ht, key);
    }

    /* Register the new key */
    id = flb_hash_table_add(env->ht, key, klen, (void *) val, vlen);
    return id;
}

const char *flb_env_get(struct flb_env *env, const char *key)
{
    int len;
    int ret;
    void *out_buf;
    size_t out_size;

    if (!key) {
        return NULL;
    }

    len = strlen(key);

    /* Try to get the value from the hash table */
    ret = flb_hash_table_get(env->ht, key, len, &out_buf, &out_size);
    if (ret >= 0) {
        return (char *) out_buf;
    }

    /* If it was not found, try to get it from the real environment */
    out_buf = getenv(key);
    if (!out_buf) {
        return NULL;
    }

    if (strlen(out_buf) == 0) {
        return NULL;
    }

    return (char *) out_buf;
}

/*
 * Given a 'value', lookup for variables, if found, return a new composed
 * sds string.
 */
flb_sds_t flb_env_var_translate(struct flb_env *env, const char *value)
{
    int i;
    int len;
    int v_len;
    int e_len;
    int pre_var;
    int have_var = FLB_FALSE;
    const char *env_var = NULL;
    char *v_start = NULL;
    char *v_end = NULL;
    char tmp[4096];
    flb_sds_t buf;
    flb_sds_t s;

    if (!value) {
        return NULL;
    }

    len = strlen(value);
    buf = flb_sds_create_size(len);
    if (!buf) {
        return NULL;
    }

    for (i = 0; i < len; i++) {
        v_start = strstr(value + i, "${");
        if (!v_start) {
            break;
        }

        v_end = strstr(value + i, "}");
        if (!v_end) {
            break;
        }

        v_start += 2;
        v_len = v_end - v_start;
        if (v_len <= 0 || v_len >= sizeof(tmp)) {
            break;
        }

        /* variable */
        strncpy(tmp, v_start, v_len);
        tmp[v_len] = '\0';
        have_var = FLB_TRUE;

        /* Append pre-variable content */
        pre_var = (v_start - 2) - (value + i);
        if (pre_var > 0) {
            s = buf_append(buf, value + i, (v_start - 2) - (value + i));
            if (!s) {
                flb_sds_destroy(buf);
                return NULL;
            }
            if (s != buf) {
                buf = s;
            }
        }

        /* Lookup the variable in our env-hash */
        env_var = flb_env_get(env, tmp);
        if (env_var) {
            e_len = strlen(env_var);
            s = buf_append(buf, env_var, e_len);
            if (!s) {
                flb_sds_destroy(buf);
                return NULL;
            }
            if (s != buf) {
                buf = s;
            }
        }
        else if (env->warn_unused == FLB_TRUE) {
            flb_warn("[env] variable ${%s} is used but not set", tmp);
        }
        i += (v_start - (value + i)) + v_len;
    }

    /* Copy the remaining value into our buffer */
    if (v_end) {
        if (have_var == FLB_TRUE && (value + len) - (v_end + 1) > 0) {
            s = buf_append(buf, v_end + 1, (value + len) - (v_end + 1));
            if (!s) {
                flb_sds_destroy(buf);
                return NULL;
            }
            if (s != buf) {
                buf = s;
            }
        }
    }

    if (flb_sds_len(buf) == 0) {
        /*
         * If the output length buffer is zero, it could mean:
         *
         * - just one variable was given and it don't have any value
         * - no variables given (keep original value)
         *
         * In order to avoid problems in the caller, if a variable is null
         * and is the only one content available, return a new empty memory
         * string.
         */
        if (have_var == FLB_TRUE) {
            return flb_sds_copy(buf, "", 0);
        }
        else {
            return flb_sds_copy(buf, value, len);
        }
    }

    return buf;
}