/*
 * Copyright (C) Maxim Dounin
 */

#include <ngx_config.h>
#include <ngx_core.h>
#include <ngx_http.h>


typedef struct {
    ngx_flag_t         enable;
} ngx_http_compose_conf_t;


static void *ngx_http_compose_create_conf(ngx_conf_t *cf);
static char *ngx_http_compose_merge_conf(ngx_conf_t *cf, void *parent,
    void *child);
static ngx_int_t ngx_http_compose_init(ngx_conf_t *cf);


static ngx_command_t  ngx_http_compose_commands[] = {

    { ngx_string("compose"),
      NGX_HTTP_MAIN_CONF|NGX_HTTP_SRV_CONF|NGX_HTTP_LOC_CONF|NGX_CONF_FLAG,
      ngx_conf_set_flag_slot,
      NGX_HTTP_LOC_CONF_OFFSET,
      offsetof(ngx_http_compose_conf_t, enable),
      NULL },

      ngx_null_command
};


static ngx_http_module_t  ngx_http_compose_module_ctx = {
    NULL,                          /* preconfiguration */
    ngx_http_compose_init,         /* postconfiguration */

    NULL,                          /* create main configuration */
    NULL,                          /* init main configuration */

    NULL,                          /* create server configuration */
    NULL,                          /* merge server configuration */

    ngx_http_compose_create_conf,  /* create location configuration */
    ngx_http_compose_merge_conf    /* merge location configuration */
};


ngx_module_t  ngx_http_compose_filter_module = {
    NGX_MODULE_V1,
    &ngx_http_compose_module_ctx,  /* module context */
    ngx_http_compose_commands,     /* module directives */
    NGX_HTTP_MODULE,               /* module type */
    NULL,                          /* init master */
    NULL,                          /* init module */
    NULL,                          /* init process */
    NULL,                          /* init thread */
    NULL,                          /* exit thread */
    NULL,                          /* exit process */
    NULL,                          /* exit master */
    NGX_MODULE_V1_PADDING
};


static ngx_http_output_header_filter_pt  ngx_http_next_header_filter;
static ngx_http_output_body_filter_pt    ngx_http_next_body_filter;


static ngx_int_t
ngx_http_compose_header_filter(ngx_http_request_t *r)
{
    ngx_http_compose_conf_t  *conf;

    conf = ngx_http_get_module_loc_conf(r, ngx_http_compose_filter_module);

    if (!conf->enable) {
        return ngx_http_next_header_filter(r);
    }

    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "compose header filter");

    return ngx_http_next_header_filter(r);
}


static ngx_int_t
ngx_http_compose_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
{
    ngx_log_debug0(NGX_LOG_DEBUG_HTTP, r->connection->log, 0,
                   "compose body filter");

    return ngx_http_next_body_filter(r, in);
}


static void *
ngx_http_compose_create_conf(ngx_conf_t *cf)
{
    ngx_http_compose_conf_t  *conf;

    conf = ngx_pcalloc(cf->pool, sizeof(ngx_http_compose_conf_t));
    if (conf == NULL) {
        return NGX_CONF_ERROR;
    }

    conf->enable = NGX_CONF_UNSET;

    return conf;
}


static char *
ngx_http_compose_merge_conf(ngx_conf_t *cf, void *parent, void *child)
{
    ngx_http_compose_conf_t *prev = parent;
    ngx_http_compose_conf_t *conf = child;

    ngx_conf_merge_value(conf->enable, prev->enable, 0);

    return NGX_CONF_OK;
}


static ngx_int_t
ngx_http_compose_init(ngx_conf_t *cf)
{
    ngx_http_next_header_filter = ngx_http_top_header_filter;
    ngx_http_top_header_filter = ngx_http_compose_header_filter;

    ngx_http_next_body_filter = ngx_http_top_body_filter;
    ngx_http_top_body_filter = ngx_http_compose_body_filter;

    return NGX_OK;
}