/*
 * Copyright (C) Igor Sysoev
 */


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


/*
 * the single part format:
 *
 * "HTTP/1.0 206 Partial Content" CRLF
 * ... header ...
 * "Content-Type: image/jpeg" CRLF
 * "Content-Length: SIZE" CRLF
 * "Content-Range: bytes START-END/SIZE" CRLF
 * CRLF
 * ... data ...
 *
 *
 * the mutlipart format:
 *
 * "HTTP/1.0 206 Partial Content" CRLF
 * ... header ...
 * "Content-Type: multipart/byteranges; boundary=0123456789" CRLF
 * CRLF
 * CRLF
 * "--0123456789" CRLF
 * "Content-Type: image/jpeg" CRLF
 * "Content-Range: bytes START0-END0/SIZE" CRLF
 * CRLF
 * ... data ...
 * CRLF
 * "--0123456789" CRLF
 * "Content-Type: image/jpeg" CRLF
 * "Content-Range: bytes START1-END1/SIZE" CRLF
 * CRLF
 * ... data ...
 * CRLF
 * "--0123456789--" CRLF
 */


typedef struct {
    off_t        start;
    off_t        end;
    ngx_str_t    content_range;
} ngx_http_range_t;


typedef struct {
    off_t        offset;
    ngx_str_t    boundary_header;
    ngx_array_t  ranges;
} ngx_http_range_filter_ctx_t;


static ngx_int_t ngx_http_range_header_filter_init(ngx_conf_t *cf);
static ngx_int_t ngx_http_range_body_filter_init(ngx_conf_t *cf);


static ngx_http_module_t  ngx_http_range_header_filter_module_ctx = {
    NULL,                                  /* preconfiguration */
    ngx_http_range_header_filter_init,     /* postconfiguration */

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

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

    NULL,                                  /* create location configuration */
    NULL,                                  /* merge location configuration */
};


ngx_module_t  ngx_http_range_header_filter_module = {
    NGX_MODULE_V1,
    &ngx_http_range_header_filter_module_ctx, /* module context */
    NULL,                                  /* 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_module_t  ngx_http_range_body_filter_module_ctx = {
    NULL,                                  /* preconfiguration */
    ngx_http_range_body_filter_init,       /* postconfiguration */

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

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

    NULL,                                  /* create location configuration */
    NULL,                                  /* merge location configuration */
};


ngx_module_t  ngx_http_range_body_filter_module = {
    NGX_MODULE_V1,
    &ngx_http_range_body_filter_module_ctx, /* module context */
    NULL,                                  /* 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_range_header_filter(ngx_http_request_t *r)
{
    u_char                       *p;
    size_t                        len;
    off_t                         start, end;
    ngx_int_t                     rc;
    ngx_uint_t                    suffix, i;
    ngx_atomic_uint_t             boundary;
    ngx_table_elt_t              *content_range;
    ngx_http_range_t             *range;
    ngx_http_range_filter_ctx_t  *ctx;

    if (r->http_version < NGX_HTTP_VERSION_10
        || r->headers_out.status != NGX_HTTP_OK
        || r != r->main
        || r->headers_out.content_length_n == -1
        || !r->allow_ranges)
    {
        return ngx_http_next_header_filter(r);
    }

    if (r->headers_in.range == NULL
        || r->headers_in.range->value.len < 7
        || ngx_strncasecmp(r->headers_in.range->value.data,
                           (u_char *) "bytes=", 6)
           != 0)
    {
        r->headers_out.accept_ranges = ngx_list_push(&r->headers_out.headers);
        if (r->headers_out.accept_ranges == NULL) {
            return NGX_ERROR;
        }

        r->headers_out.accept_ranges->hash = 1;
        r->headers_out.accept_ranges->key.len = sizeof("Accept-Ranges") - 1;
        r->headers_out.accept_ranges->key.data = (u_char *) "Accept-Ranges";
        r->headers_out.accept_ranges->value.len = sizeof("bytes") - 1;
        r->headers_out.accept_ranges->value.data = (u_char *) "bytes";

        return ngx_http_next_header_filter(r);
    }

    ctx = ngx_pcalloc(r->pool, sizeof(ngx_http_range_filter_ctx_t));
    if (ctx == NULL) {
        return NGX_ERROR;
    }

    if (ngx_array_init(&ctx->ranges, r->pool, 1, sizeof(ngx_http_range_t))
        == NGX_ERROR)
    {
        return NGX_ERROR;
    }

    rc = 0;
    range = NULL;
    p = r->headers_in.range->value.data + 6;

    for ( ;; ) {
        start = 0;
        end = 0;
        suffix = 0;

        while (*p == ' ') { p++; }

        if (*p != '-') {
            if (*p < '0' || *p > '9') {
                rc = NGX_HTTP_RANGE_NOT_SATISFIABLE;
                break;
            }

            while (*p >= '0' && *p <= '9') {
                start = start * 10 + *p++ - '0';
            }

            while (*p == ' ') { p++; }

            if (*p++ != '-') {
                rc = NGX_HTTP_RANGE_NOT_SATISFIABLE;
                break;
            }

            if (start >= r->headers_out.content_length_n) {
                rc = NGX_HTTP_RANGE_NOT_SATISFIABLE;
                break;
            }

            while (*p == ' ') { p++; }

            if (*p == ',' || *p == '\0') {
                range = ngx_array_push(&ctx->ranges);
                if (range == NULL) {
                    return NGX_ERROR;
                }

                range->start = start;
                range->end = r->headers_out.content_length_n;

                if (*p++ != ',') {
                    break;
                }

                continue;
            }

        } else {
            suffix = 1;
            p++;
        }

        if (*p < '0' || *p > '9') {
            rc = NGX_HTTP_RANGE_NOT_SATISFIABLE;
            break;
        }

        while (*p >= '0' && *p <= '9') {
            end = end * 10 + *p++ - '0';
        }

        while (*p == ' ') { p++; }

        if (*p != ',' && *p != '\0') {
            rc = NGX_HTTP_RANGE_NOT_SATISFIABLE;
            break;
        }

        if (suffix) {
           start = r->headers_out.content_length_n - end;
           end = r->headers_out.content_length_n - 1;
        }

        if (start > end) {
            rc = NGX_HTTP_RANGE_NOT_SATISFIABLE;
            break;
        }

        range = ngx_array_push(&ctx->ranges);
        if (range == NULL) {
            return NGX_ERROR;
        }

        range->start = start;

        if (end >= r->headers_out.content_length_n) {
            /*
             * Download Accelerator sends the last byte position
             * that equals to the file length
             */
            range->end = r->headers_out.content_length_n;

        } else {
            range->end = end + 1;
        }

        if (*p++ != ',') {
            break;
        }
    }

    if (rc) {

        /* rc == NGX_HTTP_RANGE_NOT_SATISFIABLE */

        r->headers_out.status = rc;

        content_range = ngx_list_push(&r->headers_out.headers);
        if (content_range == NULL) {
            return NGX_ERROR;
        }

        r->headers_out.content_range = content_range;

        content_range->hash = 1;
        content_range->key.len = sizeof("Content-Range") - 1;
        content_range->key.data = (u_char *) "Content-Range";

        content_range->value.data = ngx_palloc(r->pool,
                                       sizeof("bytes */") - 1 + NGX_OFF_T_LEN);
        if (content_range->value.data == NULL) {
            return NGX_ERROR;
        }

        content_range->value.len = ngx_sprintf(content_range->value.data,
                                               "bytes */%O",
                                               r->headers_out.content_length_n)
                                   - content_range->value.data;

        ngx_http_clear_content_length(r);

        return rc;
    }

    ngx_http_set_ctx(r, ctx, ngx_http_range_body_filter_module);

    r->headers_out.status = NGX_HTTP_PARTIAL_CONTENT;

    if (ctx->ranges.nelts == 1) {

        content_range = ngx_list_push(&r->headers_out.headers);
        if (content_range == NULL) {
            return NGX_ERROR;
        }

        r->headers_out.content_range = content_range;

        content_range->hash = 1;
        content_range->key.len = sizeof("Content-Range") - 1;
        content_range->key.data = (u_char *) "Content-Range";

        content_range->value.data =
               ngx_palloc(r->pool, sizeof("bytes -/") - 1 + 3 * NGX_OFF_T_LEN);
        if (content_range->value.data == NULL) {
            return NGX_ERROR;
        }

        /* "Content-Range: bytes SSSS-EEEE/TTTT" header */

        content_range->value.len = ngx_sprintf(content_range->value.data,
                                               "bytes %O-%O/%O",
                                               range->start, range->end - 1,
                                               r->headers_out.content_length_n)
                                   - content_range->value.data;

        r->headers_out.content_length_n = range->end - range->start;

        if (r->headers_out.content_length) {
            r->headers_out.content_length->hash = 0;
            r->headers_out.content_length = NULL;
        }

        return ngx_http_next_header_filter(r);
    }


    /* TODO: what if no content_type ?? */

    len = sizeof(CRLF "--") - 1 + NGX_ATOMIC_T_LEN
          + sizeof(CRLF "Content-Type: ") - 1
          + r->headers_out.content_type.len
          + sizeof(CRLF "Content-Range: bytes ") - 1;

    if (r->headers_out.charset.len) {
        len += sizeof("; charset=") - 1 + r->headers_out.charset.len;
    }

    ctx->boundary_header.data = ngx_palloc(r->pool, len);
    if (ctx->boundary_header.data == NULL) {
        return NGX_ERROR;
    }

    boundary = ngx_next_temp_number(0);

    /*
     * The boundary header of the range:
     * CRLF
     * "--0123456789" CRLF
     * "Content-Type: image/jpeg" CRLF
     * "Content-Range: bytes "
     */

    if (r->headers_out.charset.len) {
        ctx->boundary_header.len = ngx_sprintf(ctx->boundary_header.data,
                                           CRLF "--%0muA" CRLF
                                           "Content-Type: %V; charset=%V" CRLF
                                           "Content-Range: bytes ",
                                           boundary,
                                           &r->headers_out.content_type,
                                           &r->headers_out.charset)
                                   - ctx->boundary_header.data;

        r->headers_out.charset.len = 0;

    } else {
        ctx->boundary_header.len = ngx_sprintf(ctx->boundary_header.data,
                                           CRLF "--%0muA" CRLF
                                           "Content-Type: %V" CRLF
                                           "Content-Range: bytes ",
                                           boundary,
                                           &r->headers_out.content_type)
                                   - ctx->boundary_header.data;
    }

    r->headers_out.content_type.data =
        ngx_palloc(r->pool,
                   sizeof("Content-Type: multipart/byteranges; boundary=") - 1
                   + NGX_ATOMIC_T_LEN);

    if (r->headers_out.content_type.data == NULL) {
        return NGX_ERROR;
    }

    /* "Content-Type: multipart/byteranges; boundary=0123456789" */

    r->headers_out.content_type.len =
                           ngx_sprintf(r->headers_out.content_type.data,
                                       "multipart/byteranges; boundary=%0muA",
                                       boundary)
                           - r->headers_out.content_type.data;


    /* the size of the last boundary CRLF "--0123456789--" CRLF */

    len = sizeof(CRLF "--") - 1 + NGX_ATOMIC_T_LEN + sizeof("--" CRLF) - 1;

    range = ctx->ranges.elts;
    for (i = 0; i < ctx->ranges.nelts; i++) {

        /* the size of the range: "SSSS-EEEE/TTTT" CRLF CRLF */

        range[i].content_range.data =
                                ngx_palloc(r->pool, 3 * NGX_OFF_T_LEN + 2 + 4);

        if (range[i].content_range.data == NULL) {
            return NGX_ERROR;
        }

        range[i].content_range.len = ngx_sprintf(range[i].content_range.data,
                                               "%O-%O/%O" CRLF CRLF,
                                               range[i].start, range[i].end - 1,
                                               r->headers_out.content_length_n)
                                     - range[i].content_range.data;

        len += ctx->boundary_header.len + range[i].content_range.len
                                    + (size_t) (range[i].end - range[i].start);
    }

    r->headers_out.content_length_n = len;

    if (r->headers_out.content_length) {
        r->headers_out.content_length->hash = 0;
        r->headers_out.content_length = NULL;
    }

    return ngx_http_next_header_filter(r);
}


static ngx_int_t
ngx_http_range_body_filter(ngx_http_request_t *r, ngx_chain_t *in)
{
    off_t                         start, last;
    ngx_buf_t                    *b, *buf;
    ngx_uint_t                    i;
    ngx_chain_t                  *out, *hcl, *rcl, *dcl, **ll;
    ngx_http_range_t             *range;
    ngx_http_range_filter_ctx_t  *ctx;

    if (in == NULL) {
        return ngx_http_next_body_filter(r, in);
    }

    ctx = ngx_http_get_module_ctx(r, ngx_http_range_body_filter_module);

    if (ctx == NULL) {
        return ngx_http_next_body_filter(r, in);
    }

    buf = in->buf;

    if (ngx_buf_special(in->buf)) {
        return ngx_http_next_body_filter(r, in);
    }

    if (ctx->offset) {
        goto overlapped;
    }

    range = ctx->ranges.elts;

    if (!buf->last_buf) {

        if (buf->in_file) {
            start = buf->file_pos + ctx->offset;
            last = buf->file_last + ctx->offset;

        } else {
            start = buf->pos - buf->start + ctx->offset;
            last = buf->last - buf->start + ctx->offset;
        }

        for (i = 0; i < ctx->ranges.nelts; i++) {
            if (start > range[i].start || last < range[i].end) {
                 goto overlapped;
            }
        }
    }

    /*
     * the optimized version for the responses
     * that are passed in the single buffer
     */

    ctx->offset = ngx_buf_size(buf);

    if (ctx->ranges.nelts == 1) {

        if (buf->in_file) {
            buf->file_pos = range->start;
            buf->file_last = range->end;
        }

        if (ngx_buf_in_memory(buf)) {
            buf->pos = buf->start + (size_t) range->start;
            buf->last = buf->start + (size_t) range->end;
        }

        return ngx_http_next_body_filter(r, in);
    }

    ll = &out;

    for (i = 0; i < ctx->ranges.nelts; i++) {

        /*
         * The boundary header of the range:
         * CRLF
         * "--0123456789" CRLF
         * "Content-Type: image/jpeg" CRLF
         * "Content-Range: bytes "
         */

        b = ngx_calloc_buf(r->pool);
        if (b == NULL) {
            return NGX_ERROR;
        }

        b->memory = 1;
        b->pos = ctx->boundary_header.data;
        b->last = ctx->boundary_header.data + ctx->boundary_header.len;

        hcl = ngx_alloc_chain_link(r->pool);
        if (hcl == NULL) {
            return NGX_ERROR;
        }

        hcl->buf = b;


        /* "SSSS-EEEE/TTTT" CRLF CRLF */

        b = ngx_calloc_buf(r->pool);
        if (b == NULL) {
            return NGX_ERROR;
        }

        b->temporary = 1;
        b->pos = range[i].content_range.data;
        b->last = range[i].content_range.data + range[i].content_range.len;

        rcl = ngx_alloc_chain_link(r->pool);
        if (rcl == NULL) {
            return NGX_ERROR;
        }

        rcl->buf = b;


        /* the range data */

        b = ngx_calloc_buf(r->pool);
        if (b == NULL) {
            return NGX_ERROR;
        }

        b->in_file = buf->in_file;
        b->temporary = buf->temporary;
        b->memory = buf->memory;
        b->mmap = buf->mmap;
        b->file = buf->file;

        if (buf->in_file) {
            b->file_pos = range[i].start;
            b->file_last = range[i].end;
        }

        if (ngx_buf_in_memory(buf)) {
            b->pos = buf->start + (size_t) range[i].start;
            b->last = buf->start + (size_t) range[i].end;
        }

        dcl = ngx_alloc_chain_link(r->pool);
        if (dcl == NULL) {
            return NGX_ERROR;
        }

        dcl->buf = b;

        *ll = hcl;
        hcl->next = rcl;
        rcl->next = dcl;
        ll = &dcl->next;
    }

    /* the last boundary CRLF "--0123456789--" CRLF  */

    b = ngx_calloc_buf(r->pool);
    if (b == NULL) {
        return NGX_ERROR;
    }

    b->temporary = 1;
    b->last_buf = 1;

    b->pos = ngx_palloc(r->pool, sizeof(CRLF "--") - 1 + NGX_ATOMIC_T_LEN
                                 + sizeof("--" CRLF) - 1);
    if (b->pos == NULL) {
        return NGX_ERROR;
    }

    b->last = ngx_cpymem(b->pos, ctx->boundary_header.data,
                         sizeof(CRLF "--") - 1 + NGX_ATOMIC_T_LEN);
    *b->last++ = '-'; *b->last++ = '-';
    *b->last++ = CR; *b->last++ = LF;

    hcl = ngx_alloc_chain_link(r->pool);
    if (hcl == NULL) {
        return NGX_ERROR;
    }

    hcl->buf = b;
    hcl->next = NULL;

    *ll = hcl;

    return ngx_http_next_body_filter(r, out);

overlapped:

    ngx_log_error(NGX_LOG_ALERT, r->connection->log, 0,
                  "range in overlapped buffers");

    return NGX_ERROR;
}


static ngx_int_t
ngx_http_range_header_filter_init(ngx_conf_t *cf)
{
    ngx_http_next_header_filter = ngx_http_top_header_filter;
    ngx_http_top_header_filter = ngx_http_range_header_filter;

    return NGX_OK;
}


static ngx_int_t
ngx_http_range_body_filter_init(ngx_conf_t *cf)
{
    ngx_http_next_body_filter = ngx_http_top_body_filter;
    ngx_http_top_body_filter = ngx_http_range_body_filter;

    return NGX_OK;
}