/*	$NetBSD: http.c,v 1.40 2016/10/21 11:51:18 jperkin Exp $	*/
/*-
 * Copyright (c) 2000-2004 Dag-Erling Coïdan Smørgrav
 * Copyright (c) 2003 Thomas Klausner <wiz@NetBSD.org>
 * Copyright (c) 2008, 2009 Joerg Sonnenberger <joerg@NetBSD.org>
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer
 *    in this position and unchanged.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. The name of the author may not be used to endorse or promote products
 *    derived from this software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 *
 * $FreeBSD: http.c,v 1.83 2008/02/06 11:39:55 des Exp $
 */

/*
 * The following copyright applies to the base64 code:
 *
 *-
 * Copyright 1997 Massachusetts Institute of Technology
 *
 * Permission to use, copy, modify, and distribute this software and
 * its documentation for any purpose and without fee is hereby
 * granted, provided that both the above copyright notice and this
 * permission notice appear in all copies, that both the above
 * copyright notice and this permission notice appear in all
 * supporting documentation, and that the name of M.I.T. not be used
 * in advertising or publicity pertaining to distribution of the
 * software without specific, written prior permission.  M.I.T. makes
 * no representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied
 * warranty.
 *
 * THIS SOFTWARE IS PROVIDED BY M.I.T. ``AS IS''.  M.I.T. DISCLAIMS
 * ALL EXPRESS OR IMPLIED WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. IN NO EVENT
 * SHALL M.I.T. BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
 * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
 * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
 * ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#include <sys/types.h>
#include <sys/socket.h>
#include <ctype.h>
#include <errno.h>
#include <locale.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include <strings.h>

#include <netinet/in.h>
#include <netinet/tcp.h>
#include <netdb.h>
#include <arpa/inet.h>

#include "fetch.h"
#include "common.h"

/* Maximum number of redirects to follow */
#define MAX_REDIRECT 5

/* Symbolic names for reply codes we care about */
#define HTTP_OK 200
#define HTTP_PARTIAL 206
#define HTTP_MOVED_PERM 301
#define HTTP_MOVED_TEMP 302
#define HTTP_SEE_OTHER 303
#define HTTP_NOT_MODIFIED 304
#define HTTP_TEMP_REDIRECT 307
#define HTTP_NEED_AUTH 401
#define HTTP_NEED_PROXY_AUTH 407
#define HTTP_BAD_RANGE 416
#define HTTP_PROTOCOL_ERROR 999

#define HTTP_REDIRECT(xyz)                                                     \
    ((xyz) == HTTP_MOVED_PERM || (xyz) == HTTP_MOVED_TEMP ||                   \
     (xyz) == HTTP_TEMP_REDIRECT || (xyz) == HTTP_SEE_OTHER)

#define HTTP_ERROR(xyz) ((xyz) > 400 && (xyz) < 599)

static int http_cmd(conn_t *, const char *, ...) LIBFETCH_PRINTFLIKE(2, 3);

/*****************************************************************************
 * I/O functions for decoding chunked streams
 */

struct httpio {
    conn_t *conn;        /* connection */
    int chunked;         /* chunked mode */
    int keep_alive;      /* keep-alive mode */
    char *buf;           /* chunk buffer */
    size_t bufsize;      /* size of chunk buffer */
    ssize_t buflen;      /* amount of data currently in buffer */
    int bufpos;          /* current read offset in buffer */
    int eof;             /* end-of-file flag */
    int error;           /* error flag */
    size_t chunksize;    /* remaining size of current chunk */
    off_t contentlength; /* remaining size of the content */
};

/*
 * Get next chunk header
 */
static int http_new_chunk(struct httpio *io)
{
    const char *p;

    if (fetch_getln(io->conn) == -1)
        return -1;

    if (io->conn->buflen < 2)
        return -1;

    io->chunksize = fetch_parseuint(io->conn->buf, &p, 16, SIZE_MAX);
    if (*p && *p != ';' && !isspace(*p))
        return -1;

    return io->chunksize;
}

/*
 * Grow the input buffer to at least len bytes
 */
static int http_growbuf(struct httpio *io, size_t len)
{
    char *tmp;

    if (io->bufsize >= len)
        return (0);

    if ((tmp = realloc(io->buf, len)) == NULL)
        return (-1);
    io->buf = tmp;
    io->bufsize = len;
    return (0);
}

/*
 * Fill the input buffer, do chunk decoding on the fly
 */
static int http_fillbuf(struct httpio *io, size_t len)
{
    if (io->error)
        return (-1);
    if (io->eof)
        return (0);

    if (io->contentlength >= 0 && (off_t)len > io->contentlength)
        len = io->contentlength;

    if (io->chunked == 0) {
        if (http_growbuf(io, len) == -1)
            return (-1);
        if ((io->buflen = fetch_read(io->conn, io->buf, len)) == -1) {
            io->error = 1;
            return (-1);
        }
        if (io->contentlength)
            io->contentlength -= io->buflen;
        io->bufpos = 0;
        return (io->buflen);
    }

    if (io->chunksize == 0) {
        switch (http_new_chunk(io)) {
        case -1:
            io->error = 1;
            return (-1);
        case 0:
            io->eof = 1;
            if (fetch_getln(io->conn) == -1)
                return (-1);
            return (0);
        }
    }

    if (len > io->chunksize)
        len = io->chunksize;
    if (http_growbuf(io, len) == -1)
        return (-1);
    if ((io->buflen = fetch_read(io->conn, io->buf, len)) == -1) {
        io->error = 1;
        return (-1);
    }
    io->chunksize -= io->buflen;
    if (io->contentlength >= 0)
        io->contentlength -= io->buflen;

    if (io->chunksize == 0) {
        char endl[2];
        ssize_t len2;

        len2 = fetch_read(io->conn, endl, 2);
        if (len2 == 1 && fetch_read(io->conn, endl + 1, 1) != 1)
            return (-1);
        if (len2 == -1 || endl[0] != '\r' || endl[1] != '\n')
            return (-1);
    }

    io->bufpos = 0;

    return (io->buflen);
}

/*
 * Read function
 */
static ssize_t http_readfn(void *v, void *buf, size_t len)
{
    struct httpio *io = (struct httpio *)v;
    size_t l, pos;

    if (io->error)
        return (-1);
    if (io->eof)
        return (0);

    for (pos = 0; len > 0; pos += l, len -= l) {
        /* empty buffer */
        if (!io->buf || io->bufpos == io->buflen)
            if (http_fillbuf(io, len) < 1)
                break;
        l = io->buflen - io->bufpos;
        if (len < l)
            l = len;
        memcpy((char *)buf + pos, io->buf + io->bufpos, l);
        io->bufpos += l;
    }

    if (!pos && io->error)
        return (-1);
    return (pos);
}

/*
 * Write function
 */
static ssize_t http_writefn(void *v, const void *buf, size_t len)
{
    struct httpio *io = (struct httpio *)v;

    return (fetch_write(io->conn, buf, len));
}

/*
 * Close function
 */
static void http_closefn(void *v)
{
    struct httpio *io = (struct httpio *)v;
    conn_t *conn = io->conn;

    if (io->keep_alive) {
        fetch_cache_put(conn, fetch_close);
    } else {
        fetch_close(conn);
    }

    free(io->buf);
    free(io);
}

/*
 * Wrap a file descriptor up
 */
static fetchIO *http_funopen(conn_t *conn, int chunked, int keep_alive,
                             off_t clength)
{
    struct httpio *io;
    fetchIO *f;

    if ((io = calloc(1, sizeof(*io))) == NULL) {
        fetch_syserr();
        return (NULL);
    }
    io->conn = conn;
    io->chunked = chunked;
    io->contentlength = clength;
    io->keep_alive = keep_alive;
    f = fetchIO_unopen(io, http_readfn, http_writefn, http_closefn);
    if (f == NULL) {
        fetch_syserr();
        free(io);
        return (NULL);
    }
    return (f);
}

/*****************************************************************************
 * Helper functions for talking to the server and parsing its replies
 */

/* Header types */
typedef enum {
    hdr_syserror = -2,
    hdr_error = -1,
    hdr_end = 0,
    hdr_unknown = 1,
    hdr_connection,
    hdr_content_length,
    hdr_content_range,
    hdr_last_modified,
    hdr_location,
    hdr_transfer_encoding,
    hdr_www_authenticate
} hdr_t;

/* Names of interesting headers */
static struct {
    hdr_t num;
    const char *name;
} hdr_names[] = {
    {hdr_connection, "Connection"},
    {hdr_content_length, "Content-Length"},
    {hdr_content_range, "Content-Range"},
    {hdr_last_modified, "Last-Modified"},
    {hdr_location, "Location"},
    {hdr_transfer_encoding, "Transfer-Encoding"},
    {hdr_www_authenticate, "WWW-Authenticate"},
    {hdr_unknown, NULL},
};

/*
 * Send a formatted line; optionally echo to terminal
 */
LIBFETCH_PRINTFLIKE(2, 3)
static int http_cmd(conn_t *conn, const char *fmt, ...)
{
    va_list ap;
    size_t len;
    char *msg;
    int r;

    va_start(ap, fmt);
    len = vasprintf(&msg, fmt, ap);
    va_end(ap);

    if (msg == NULL) {
        errno = ENOMEM;
        fetch_syserr();
        return (-1);
    }

    r = fetch_write(conn, msg, len);
    free(msg);

    if (r == -1) {
        fetch_syserr();
        return (-1);
    }

    return (0);
}

/*
 * Get and parse status line
 */
static int http_get_reply(conn_t *conn)
{
    char *p;

    if (fetch_getln(conn) == -1)
        return (-1);
    /*
     * A valid status line looks like "HTTP/m.n xyz reason" where m
     * and n are the major and minor protocol version numbers and xyz
     * is the reply code.
     * Unfortunately, there are servers out there (NCSA 1.5.1, to name
     * just one) that do not send a version number, so we can't rely
     * on finding one, but if we do, insist on it being 1.0 or 1.1.
     * We don't care about the reason phrase.
     */
    if (strncmp(conn->buf, "HTTP", 4) != 0)
        return (HTTP_PROTOCOL_ERROR);
    p = conn->buf + 4;
    if (*p == '/') {
        if (p[1] != '1' || p[2] != '.' || (p[3] != '0' && p[3] != '1'))
            return (HTTP_PROTOCOL_ERROR);
        p += 4;
    }
    if (*p != ' ' || !isdigit((unsigned char)p[1]) ||
        !isdigit((unsigned char)p[2]) || !isdigit((unsigned char)p[3]))
        return (HTTP_PROTOCOL_ERROR);

    conn->err = (p[1] - '0') * 100 + (p[2] - '0') * 10 + (p[3] - '0');
    return (conn->err);
}

/*
 * Check a header; if the type matches the given string, return a pointer
 * to the beginning of the value.
 */
static const char *http_match(const char *str, const char *hdr)
{
    while (*str && *hdr &&
           tolower((unsigned char)*str++) == tolower((unsigned char)*hdr++))
        /* nothing */;
    if (*str || *hdr != ':')
        return (NULL);
    while (*hdr && isspace((unsigned char)*++hdr))
        /* nothing */;
    return (hdr);
}

/*
 * Get the next header and return the appropriate symbolic code.
 */
static hdr_t http_next_header(conn_t *conn, const char **p)
{
    int i;

    if (fetch_getln(conn) == -1)
        return (hdr_syserror);
    while (conn->buflen && isspace((unsigned char)conn->buf[conn->buflen - 1]))
        conn->buflen--;
    conn->buf[conn->buflen] = '\0';
    if (conn->buflen == 0)
        return (hdr_end);
    /*
     * We could check for malformed headers but we don't really care.
     * A valid header starts with a token immediately followed by a
     * colon; a token is any sequence of non-control, non-whitespace
     * characters except "()<>@,;:\\\"{}".
     */
    for (i = 0; hdr_names[i].num != hdr_unknown; i++)
        if ((*p = http_match(hdr_names[i].name, conn->buf)) != NULL)
            return (hdr_names[i].num);
    return (hdr_unknown);
}

/*
 * Parse a last-modified header
 */
static int http_parse_mtime(const char *p, time_t *mtime)
{
    char *locale, *r;
    struct tm tm;

    locale = strdup(setlocale(LC_TIME, NULL));
    setlocale(LC_TIME, "C");
    /* RFC2616 §3.3.1 requires compliant client to accept the Internet
     * standard, and the two obsolete, date formats:
     *  Sun, 06 Nov 1994 08:49:37 GMT  ; RFC 822, updated by RFC 1123
     *  Sunday, 06-Nov-94 08:49:37 GMT ; RFC 850, obsoleted by RFC 1036
     *  Sun Nov  6 08:49:37 1994       ; ANSI C's asctime() format
     */
    r = strptime(p, "%a, %d %b %Y %H:%M:%S GMT", &tm);
    if (!r)
        r = strptime(p, "%A, %d-%b-%y %H:%M:%S GMT", &tm);
    if (!r)
        r = strptime(p, "%a %b %d %H:%M:%S %Y", &tm);
    setlocale(LC_TIME, locale);
    free(locale);
    if (r == NULL)
        return (-1);
    *mtime = timegm(&tm);
    return (0);
}

/*
 * Parse a content-range header
 */
static int http_parse_range(const char *p, off_t *offset, off_t *length,
                            off_t *size)
{
    off_t first, last, len;

    if (strncasecmp(p, "bytes ", 6) != 0)
        return (-1);
    p += 6;
    if (*p == '*') {
        first = last = -1;
        ++p;
    } else {
        first = fetch_parseuint(p, &p, 10, OFF_MAX);
        if (*p != '-')
            return (-1);
        last = fetch_parseuint(p + 1, &p, 10, OFF_MAX);
    }
    if (first > last || *p != '/')
        return (-1);
    len = fetch_parseuint(p + 1, &p, 10, OFF_MAX);
    if (*p || len < last - first + 1)
        return (-1);
    if (first == -1)
        *length = 0;
    else
        *length = last - first + 1;
    *offset = first;
    *size = len;
    return (0);
}

/*****************************************************************************
 * Helper functions for authorization
 */

/*
 * Base64 encoding
 */
static char *http_base64(const char *src)
{
    static const char base64[] = "ABCDEFGHIJKLMNOPQRSTUVWXYZ"
                                 "abcdefghijklmnopqrstuvwxyz"
                                 "0123456789+/";
    char *str, *dst;
    size_t l;
    int t;

    l = strlen(src);
    if ((str = malloc(((l + 2) / 3) * 4 + 1)) == NULL)
        return (NULL);
    dst = str;

    while (l >= 3) {
        t = (src[0] << 16) | (src[1] << 8) | src[2];
        dst[0] = base64[(t >> 18) & 0x3f];
        dst[1] = base64[(t >> 12) & 0x3f];
        dst[2] = base64[(t >> 6) & 0x3f];
        dst[3] = base64[(t >> 0) & 0x3f];
        src += 3;
        l -= 3;
        dst += 4;
    }

    switch (l) {
    case 2:
        t = (src[0] << 16) | (src[1] << 8);
        dst[0] = base64[(t >> 18) & 0x3f];
        dst[1] = base64[(t >> 12) & 0x3f];
        dst[2] = base64[(t >> 6) & 0x3f];
        dst[3] = '=';
        dst += 4;
        break;
    case 1:
        t = src[0] << 16;
        dst[0] = base64[(t >> 18) & 0x3f];
        dst[1] = base64[(t >> 12) & 0x3f];
        dst[2] = dst[3] = '=';
        dst += 4;
        break;
    case 0:
        break;
    }

    *dst = 0;
    return (str);
}

/*
 * Encode username and password
 */
static int http_basic_auth(conn_t *conn, const char *hdr, const char *usr,
                           const char *pwd)
{
    char *upw, *auth;
    int r;

    if (asprintf(&upw, "%s:%s", usr, pwd) == -1)
        return (-1);
    auth = http_base64(upw);
    free(upw);
    if (auth == NULL)
        return (-1);
    r = http_cmd(conn, "%s: Basic %s\r\n", hdr, auth);
    free(auth);
    return (r);
}

/*
 * Send an authorization header
 */
static int http_authorize(conn_t *conn, const char *hdr, const char *p)
{
    /* basic authorization */
    if (strncasecmp(p, "basic:", 6) == 0) {
        char *user, *pwd, *str;
        int r;

        /* skip realm */
        for (p += 6; *p && *p != ':'; ++p)
            /* nothing */;
        if (!*p || strchr(++p, ':') == NULL)
            return (-1);
        if ((str = strdup(p)) == NULL)
            return (-1); /* XXX */
        user = str;
        pwd = strchr(str, ':');
        *pwd++ = '\0';
        r = http_basic_auth(conn, hdr, user, pwd);
        free(str);
        return (r);
    }
    return (-1);
}

/*
 * Send a Proxy authorization header
 */
static void http_proxy_authorize(conn_t *conn, struct url *purl)
{
    const char *p;

    if (!purl)
        return;
    if (*purl->user || *purl->pwd)
        http_basic_auth(conn, "Proxy-Authorization", purl->user, purl->pwd);
    else if ((p = getenv("HTTP_PROXY_AUTH")) != NULL && *p != '\0')
        http_authorize(conn, "Proxy-Authorization", p);
}

/*****************************************************************************
 * Helper functions for connecting to a server or proxy
 */

/*
 * Helper for setting socket options regarding packetization
 */
static void http_cork(conn_t *conn, int val)
{
#if defined(TCP_CORK)
    setsockopt(conn->sd, IPPROTO_TCP, TCP_CORK, &val, sizeof val);
#else
#if defined(TCP_NOPUSH) && !defined(__APPLE__)
    setsockopt(conn->sd, IPPROTO_TCP, TCP_NOPUSH, &val, sizeof val);
#endif
    val = !val;
    setsockopt(conn->sd, IPPROTO_TCP, TCP_NODELAY, &val, sizeof val);
#endif
}

/*
 * Connect to the correct HTTP server or proxy.
 */
static conn_t *http_connect(struct url *URL, struct url *purl,
                            const char *flags, int *cached)
{
    struct url *cache_url;
    conn_t *conn;
    hdr_t h;
    const char *p;
    int af, verbose, is_https;

    *cached = 0;
    af = AF_UNSPEC;
    verbose = CHECK_FLAG('v');
    if (CHECK_FLAG('4'))
        af = AF_INET;
    else if (CHECK_FLAG('6'))
        af = AF_INET6;

    is_https = strcasecmp(URL->scheme, SCHEME_HTTPS) == 0;
    cache_url = (is_https || !purl) ? URL : purl;

    if ((conn = fetch_cache_get(cache_url, af)) != NULL) {
        *cached = 1;
        return (conn);
    }

    if ((conn = fetch_connect(cache_url, purl ? purl : URL, af, verbose)) == NULL)
        /* fetch_connect() has already set an error code */
        return (NULL);

    if (is_https && purl) {
        http_cork(conn, 1);
        http_cmd(conn, "CONNECT %s:%d HTTP/1.1\r\nHost: %s:%d\r\n", URL->host,
                 URL->port, URL->host, URL->port);
        http_proxy_authorize(conn, purl);
        http_cmd(conn, "\r\n");
        http_cork(conn, 0);
        if (http_get_reply(conn) != HTTP_OK) {
            http_seterr(conn->err);
            goto ouch;
        }
        do {
            switch ((h = http_next_header(conn, &p))) {
            case hdr_syserror:
                fetch_syserr();
                goto ouch;
            case hdr_error:
                http_seterr(HTTP_PROTOCOL_ERROR);
                goto ouch;
            default:
                /* ignore */;
            }
        } while (h > hdr_end);
    }
    if (is_https && fetch_ssl(conn, URL, verbose) == -1) {
        goto ouch;
    }
    return (conn);
ouch:
    fetch_close(conn);
    return (NULL);
}

static struct url *http_make_proxy_url(const char *env1, const char *env2)
{
    struct url *purl;
    char *p;

    p = getenv(env1);
    if (!p)
        p = getenv(env2);
    if (!p || !*p)
        return NULL;

    purl = fetchParseURL(p);
    if (!purl)
        return NULL;

    if (!*purl->scheme)
        strcpy(purl->scheme, SCHEME_HTTP);
    if (!purl->port)
        purl->port = fetch_default_proxy_port(purl->scheme);

    if (strcasecmp(purl->scheme, SCHEME_HTTP) == 0)
        return purl;

    fetchFreeURL(purl);
    return NULL;
}

static struct url *http_get_proxy(struct url *url, const char *flags)
{
    if (flags != NULL && strchr(flags, 'd') != NULL)
        return (NULL);
    if (fetch_no_proxy_match(url->host))
        return (NULL);
    if (strcasecmp(url->scheme, SCHEME_HTTPS) == 0)
        return http_make_proxy_url("HTTPS_PROXY", "https_proxy");
    if (strcasecmp(url->scheme, SCHEME_HTTP) == 0)
        return http_make_proxy_url("HTTP_PROXY", "http_proxy");
    return (NULL);
}

static void set_if_modified_since(conn_t *conn, time_t last_modified)
{
    static const char weekdays[] = "SunMonTueWedThuFriSat";
    static const char months[] = "JanFebMarAprMayJunJulAugSepOctNovDec";
    struct tm tm;
    char buf[80];
    gmtime_r(&last_modified, &tm);
    snprintf(buf, sizeof(buf), "%.3s, %02d %.3s %4ld %02d:%02d:%02d GMT",
             weekdays + tm.tm_wday * 3, tm.tm_mday, months + tm.tm_mon * 3,
             (long)(tm.tm_year + 1900), tm.tm_hour, tm.tm_min, tm.tm_sec);
    http_cmd(conn, "If-Modified-Since: %s\r\n", buf);
}

/*****************************************************************************
 * Core
 */

/*
 * Send a request and process the reply
 *
 * XXX This function is way too long, the do..while loop should be split
 * XXX off into a separate function.
 */
static fetchIO *http_request(struct url *URL, const char *op,
                             struct url_stat *us, struct url *purl,
                             const char *flags)
{
    conn_t *conn;
    struct url *url, *new;
    int chunked, direct, if_modified_since, need_auth, noredirect, nocache;
    int keep_alive, verbose, cached;
    int e, i, n;
    off_t offset, clength, length, size;
    time_t mtime;
    const char *p, *q;
    fetchIO *f;
    hdr_t h;
    char hbuf[URL_HOSTLEN + 7], *host;

    direct = CHECK_FLAG('d');
    noredirect = CHECK_FLAG('A');
    nocache = CHECK_FLAG('C');
    verbose = CHECK_FLAG('v');
    if_modified_since = CHECK_FLAG('i');
    keep_alive = 0;

    if (direct && purl) {
        fetchFreeURL(purl);
        purl = NULL;
    }

    /* try the provided URL first */
    url = URL;

    /* if the A flag is set, we only get one try */
    n = noredirect ? 1 : MAX_REDIRECT;
    i = 0;

    e = HTTP_PROTOCOL_ERROR;
    need_auth = 0;
    do {
        new = NULL;
        chunked = 0;
        offset = 0;
        clength = -1;
        length = -1;
        size = -1;
        mtime = 0;

        /* check port */
        if (!url->port)
            url->port = fetch_default_port(url->scheme);

        /* connect to server or proxy */
        if ((conn = http_connect(url, purl, flags, &cached)) == NULL)
            goto ouch;

        host = url->host;
        if (strchr(url->host, ':')) {
            snprintf(hbuf, sizeof(hbuf), "[%s]", url->host);
            host = hbuf;
        }
        if (url->port != fetch_default_port(url->scheme)) {
            if (host != hbuf) {
                strcpy(hbuf, host);
                host = hbuf;
            }
            snprintf(hbuf + strlen(hbuf), sizeof(hbuf) - strlen(hbuf), ":%d",
                     url->port);
        }

        /* send request */
        if (verbose)
            fetch_info("requesting %s://%s%s", url->scheme, host, url->doc);

        http_cork(conn, 1);
        if (purl && strcasecmp(URL->scheme, SCHEME_HTTPS) != 0) {
            http_cmd(conn, "%s %s://%s%s HTTP/1.1\r\n", op, url->scheme, host,
                     url->doc);
        } else {
            http_cmd(conn, "%s %s HTTP/1.1\r\n", op, url->doc);
        }

        if (nocache)
            http_cmd(conn, "Cache-Control: no-cache\r\n");
        if (if_modified_since && url->last_modified > 0)
            set_if_modified_since(conn, url->last_modified);

        /* virtual host */
        http_cmd(conn, "Host: %s\r\n", host);

        /* proxy authorization */
        http_proxy_authorize(conn, purl);

        if (need_auth && !*url->pwd && !*url->user)
            fetch_netrc_auth(url);
        /* server authorization */
        if (need_auth || *url->user || *url->pwd) {
            if (*url->user || *url->pwd)
                http_basic_auth(conn, "Authorization", url->user, url->pwd);
            else if ((p = getenv("HTTP_AUTH")) != NULL && *p != '\0')
                http_authorize(conn, "Authorization", p);
            else if (fetchAuthMethod && fetchAuthMethod(url) == 0) {
                http_basic_auth(conn, "Authorization", url->user, url->pwd);
            } else {
                http_seterr(HTTP_NEED_AUTH);
                goto ouch;
            }
        }

        /* other headers */
        if ((p = getenv("HTTP_REFERER")) != NULL && *p != '\0') {
            if (strcasecmp(p, "auto") == 0)
                http_cmd(conn, "Referer: %s://%s%s\r\n", url->scheme, host,
                         url->doc);
            else
                http_cmd(conn, "Referer: %s\r\n", p);
        }
        if ((p = getenv("HTTP_USER_AGENT")) != NULL && *p != '\0')
            http_cmd(conn, "User-Agent: %s\r\n", p);
        else
            http_cmd(conn, "User-Agent: %s\r\n", _LIBFETCH_VER);
        if (url->offset > 0)
            http_cmd(conn, "Range: bytes=%lld-\r\n", (long long)url->offset);
        http_cmd(conn, "\r\n");

        /*
         * Force the queued request to be dispatched.  Normally, one
         * would do this with shutdown(2) but squid proxies can be
         * configured to disallow such half-closed connections.  To
         * be compatible with such configurations, fiddle with socket
         * options to force the pending data to be written.
         */
        http_cork(conn, 0);

        /* get reply */
        switch (http_get_reply(conn)) {
        case HTTP_OK:
        case HTTP_PARTIAL:
        case HTTP_NOT_MODIFIED:
            /* fine */
            break;
        case HTTP_MOVED_PERM:
        case HTTP_MOVED_TEMP:
        case HTTP_SEE_OTHER:
            /*
             * Not so fine, but we still have to read the
             * headers to get the new location.
             */
            break;
        case HTTP_NEED_AUTH:
            if (need_auth) {
                /*
                 * We already sent out authorization code,
                 * so there's nothing more we can do.
                 */
                http_seterr(conn->err);
                goto ouch;
            }
            /* try again, but send the password this time */
            if (verbose)
                fetch_info("server requires authorization");
            break;
        case HTTP_NEED_PROXY_AUTH:
            /*
             * If we're talking to a proxy, we already sent
             * our proxy authorization code, so there's
             * nothing more we can do.
             */
            http_seterr(conn->err);
            goto ouch;
        case HTTP_BAD_RANGE:
            /*
             * This can happen if we ask for 0 bytes because
             * we already have the whole file.  Consider this
             * a success for now, and check sizes later.
             */
            break;
        case HTTP_PROTOCOL_ERROR:
            /* fall through */
        case -1:
            --i;
            if (cached)
                continue;
            fetch_syserr();
            goto ouch;
        default:
            http_seterr(conn->err);
            if (!verbose)
                goto ouch;
            /* fall through so we can get the full error message */
        }

        /* get headers */
        do {
            switch ((h = http_next_header(conn, &p))) {
            case hdr_syserror:
                fetch_syserr();
                goto ouch;
            case hdr_error:
                goto protocol_error;
            case hdr_connection:
                /* XXX too weak? */
                keep_alive = (strcasecmp(p, "keep-alive") == 0);
                break;
            case hdr_content_length:
                clength = fetch_parseuint(p, &q, 10, OFF_MAX);
                if (*q)
                    goto protocol_error;
                break;
            case hdr_content_range:
                if (http_parse_range(p, &offset, &length, &size) < 0)
                    goto protocol_error;
                break;
            case hdr_last_modified:
                if (http_parse_mtime(p, &mtime) < 0)
                    goto protocol_error;
                break;
            case hdr_location:
                if (!HTTP_REDIRECT(conn->err))
                    break;
                if (new)
                    free(new);
                if (verbose)
                    fetch_info("%d redirect to %s", conn->err, p);
                if (*p == '/')
                    /* absolute path */
                    new = fetchMakeURL(url->scheme, url->host, url->port, p,
                                       url->user, url->pwd);
                else
                    new = fetchParseURL(p);
                if (new == NULL) {
                    /* XXX should set an error code */
                    goto ouch;
                }
                if (!new->port)
                    new->port = fetch_default_port(new->scheme);
                if (!new->user[0] && !new->pwd[0] && new->port == url->port &&
                    strcmp(new->scheme, url->scheme) == 0 &&
                    strcmp(new->host, url->host) == 0) {
                    /* keep auth if staying on same host */
                    strcpy(new->user, url->user);
                    strcpy(new->pwd, url->pwd);
                }
                new->offset = url->offset;
                new->length = url->length;
                if (fetchRedirectMethod)
                    fetchRedirectMethod(conn->err, url, new);
                break;
            case hdr_transfer_encoding:
                /* XXX weak test*/
                chunked = (strcasecmp(p, "chunked") == 0);
                break;
            case hdr_www_authenticate:
                if (conn->err != HTTP_NEED_AUTH)
                    break;
                /* if we were smarter, we'd check the method and realm */
                break;
            case hdr_end:
                /* fall through */
            case hdr_unknown:
                /* ignore */
                break;
            }
        } while (h > hdr_end);

        /* we need to provide authentication */
        if (conn->err == HTTP_NEED_AUTH) {
            e = conn->err;
            need_auth = 1;
            fetch_close(conn);
            conn = NULL;
            continue;
        }

        /* requested range not satisfiable */
        if (conn->err == HTTP_BAD_RANGE) {
            if (url->offset == size && url->length == 0) {
                /* asked for 0 bytes; fake it */
                offset = url->offset;
                conn->err = HTTP_OK;
                break;
            } else {
                http_seterr(conn->err);
                goto ouch;
            }
        }

        /* we have a hit or an error */
        if (conn->err == HTTP_OK || conn->err == HTTP_PARTIAL ||
            conn->err == HTTP_NOT_MODIFIED || HTTP_ERROR(conn->err))
            break;

        /* all other cases: we got a redirect */
        e = conn->err;
        need_auth = 0;
        fetch_close(conn);
        conn = NULL;
        if (!new)
            break;
        if (url != URL)
            fetchFreeURL(url);
        url = new;
    } while (++i < n);

    /* we failed, or ran out of retries */
    if (conn == NULL) {
        http_seterr(e);
        goto ouch;
    }

    /* check for inconsistencies */
    if (clength != -1 && length != -1 && clength != length)
        goto protocol_error;
    if (clength == -1)
        clength = length;
    if (clength != -1)
        length = offset + clength;
    if (length != -1 && size != -1 && length != size)
        goto protocol_error;
    if (size == -1)
        size = length;

    /* fill in stats */
    if (us) {
        us->size = size;
        us->atime = us->mtime = mtime;
    }

    /* too far? */
    if (URL->offset > 0 && offset > URL->offset)
        goto protocol_error;

    /* report back real offset and size */
    URL->offset = offset;
    URL->length = clength;

    if (clength == -1 && !chunked)
        keep_alive = 0;

    if (conn->err == HTTP_NOT_MODIFIED) {
        http_seterr(HTTP_NOT_MODIFIED);
        if (keep_alive) {
            fetch_cache_put(conn, fetch_close);
            conn = NULL;
        }
        goto ouch;
    }

    /* wrap it up in a fetchIO */
    if ((f = http_funopen(conn, chunked, keep_alive, clength)) == NULL) {
        fetch_syserr();
        goto ouch;
    }

    if (url != URL)
        fetchFreeURL(url);
    if (purl)
        fetchFreeURL(purl);

    if (HTTP_ERROR(conn->err)) {

        if (keep_alive) {
            char buf[512];
            do {
            } while (fetchIO_read(f, buf, sizeof(buf)) > 0);
        }

        fetchIO_close(f);
        f = NULL;
    }

    return (f);

protocol_error:
    http_seterr(HTTP_PROTOCOL_ERROR);
ouch:
    if (url != URL)
        fetchFreeURL(url);
    if (purl)
        fetchFreeURL(purl);
    if (conn != NULL)
        fetch_close(conn);
    return (NULL);
}

/*****************************************************************************
 * Entry points
 */

/*
 * Retrieve and stat a file by HTTP
 */
fetchIO *fetchXGetHTTP(struct url *URL, struct url_stat *us, const char *flags)
{
    return (http_request(URL, "GET", us, http_get_proxy(URL, flags), flags));
}

/*
 * Retrieve a file by HTTP
 */
fetchIO *fetchGetHTTP(struct url *URL, const char *flags)
{
    return (fetchXGetHTTP(URL, NULL, flags));
}

/*
 * Store a file by HTTP
 */
fetchIO *fetchPutHTTP(struct url *URL, const char *flags)
{
    (void)URL;
    (void)flags;

    fprintf(stderr, "fetchPutHTTP(): not implemented\n");
    return (NULL);
}

/*
 * Get an HTTP document's metadata
 */
int fetchStatHTTP(struct url *URL, struct url_stat *us, const char *flags)
{
    fetchIO *f;

    f = http_request(URL, "HEAD", us, http_get_proxy(URL, flags), flags);
    if (f == NULL)
        return (-1);
    fetchIO_close(f);
    return (0);
}

enum http_states {
    ST_NONE,
    ST_LT,
    ST_LTA,
    ST_TAGA,
    ST_H,
    ST_R,
    ST_E,
    ST_F,
    ST_HREF,
    ST_HREFQ,
    ST_TAG,
    ST_TAGAX,
    ST_TAGAQ
};

struct index_parser {
    struct url_list *ue;
    struct url *url;
    enum http_states state;
};

static ssize_t parse_index(struct index_parser *parser, char *buf, size_t len)
{
    char *end_attr, p = *buf;

    switch (parser->state) {
    case ST_NONE:
        /* Plain text, not in markup */
        if (p == '<')
            parser->state = ST_LT;
        return 1;
    case ST_LT:
        /* In tag -- "<" already found */
        if (p == '>')
            parser->state = ST_NONE;
        else if (p == 'a' || p == 'A')
            parser->state = ST_LTA;
        else if (!isspace((unsigned char)p))
            parser->state = ST_TAG;
        return 1;
    case ST_LTA:
        /* In tag -- "<a" already found */
        if (p == '>')
            parser->state = ST_NONE;
        else if (p == '"')
            parser->state = ST_TAGAQ;
        else if (isspace((unsigned char)p))
            parser->state = ST_TAGA;
        else
            parser->state = ST_TAG;
        return 1;
    case ST_TAG:
        /* In tag, but not "<a" -- disregard */
        if (p == '>')
            parser->state = ST_NONE;
        return 1;
    case ST_TAGA:
        /* In a-tag -- "<a " already found */
        if (p == '>')
            parser->state = ST_NONE;
        else if (p == '"')
            parser->state = ST_TAGAQ;
        else if (p == 'h' || p == 'H')
            parser->state = ST_H;
        else if (!isspace((unsigned char)p))
            parser->state = ST_TAGAX;
        return 1;
    case ST_TAGAX:
        /* In unknown keyword in a-tag */
        if (p == '>')
            parser->state = ST_NONE;
        else if (p == '"')
            parser->state = ST_TAGAQ;
        else if (isspace((unsigned char)p))
            parser->state = ST_TAGA;
        return 1;
    case ST_TAGAQ:
        /* In a-tag, unknown argument for keys. */
        if (p == '>')
            parser->state = ST_NONE;
        else if (p == '"')
            parser->state = ST_TAGA;
        return 1;
    case ST_H:
        /* In a-tag -- "<a h" already found */
        if (p == '>')
            parser->state = ST_NONE;
        else if (p == '"')
            parser->state = ST_TAGAQ;
        else if (p == 'r' || p == 'R')
            parser->state = ST_R;
        else if (isspace((unsigned char)p))
            parser->state = ST_TAGA;
        else
            parser->state = ST_TAGAX;
        return 1;
    case ST_R:
        /* In a-tag -- "<a hr" already found */
        if (p == '>')
            parser->state = ST_NONE;
        else if (p == '"')
            parser->state = ST_TAGAQ;
        else if (p == 'e' || p == 'E')
            parser->state = ST_E;
        else if (isspace((unsigned char)p))
            parser->state = ST_TAGA;
        else
            parser->state = ST_TAGAX;
        return 1;
    case ST_E:
        /* In a-tag -- "<a hre" already found */
        if (p == '>')
            parser->state = ST_NONE;
        else if (p == '"')
            parser->state = ST_TAGAQ;
        else if (p == 'f' || p == 'F')
            parser->state = ST_F;
        else if (isspace((unsigned char)p))
            parser->state = ST_TAGA;
        else
            parser->state = ST_TAGAX;
        return 1;
    case ST_F:
        /* In a-tag -- "<a href" already found */
        if (p == '>')
            parser->state = ST_NONE;
        else if (p == '"')
            parser->state = ST_TAGAQ;
        else if (p == '=')
            parser->state = ST_HREF;
        else if (!isspace((unsigned char)p))
            parser->state = ST_TAGAX;
        return 1;
    case ST_HREF:
        /* In a-tag -- "<a href=" already found */
        if (p == '>')
            parser->state = ST_NONE;
        else if (p == '"')
            parser->state = ST_HREFQ;
        else if (!isspace((unsigned char)p))
            parser->state = ST_TAGA;
        return 1;
    case ST_HREFQ:
        /* In href of the a-tag */
        end_attr = memchr(buf, '"', len);
        if (end_attr == NULL)
            return 0;
        *end_attr = '\0';
        parser->state = ST_TAGA;
        if (fetch_add_entry(parser->ue, parser->url, buf, 1))
            return -1;
        return end_attr + 1 - buf;
    }
    /* NOTREACHED */
    abort();
}

struct http_index_cache {
    struct http_index_cache *next;
    struct url *location;
    struct url_list ue;
};

static struct http_index_cache *index_cache;

/*
 * List a directory
 */
int fetchListHTTP(struct url_list *ue, struct url *url, const char *pattern,
                  const char *flags)
{
    (void)pattern;

    fetchIO *f;
    char buf[2 * PATH_MAX];
    size_t buf_len, sum_processed;
    ssize_t read_len, processed;
    struct index_parser state;
    struct http_index_cache *cache = NULL;
    int do_cache, ret;

    do_cache = CHECK_FLAG('c');

    if (do_cache) {
        for (cache = index_cache; cache != NULL; cache = cache->next) {
            if (strcmp(cache->location->scheme, url->scheme))
                continue;
            if (strcmp(cache->location->user, url->user))
                continue;
            if (strcmp(cache->location->pwd, url->pwd))
                continue;
            if (strcmp(cache->location->host, url->host))
                continue;
            if (cache->location->port != url->port)
                continue;
            if (strcmp(cache->location->doc, url->doc))
                continue;
            return fetchAppendURLList(ue, &cache->ue);
        }

        cache = malloc(sizeof(*cache));
        fetchInitURLList(&cache->ue);
        cache->location = fetchCopyURL(url);
    }

    f = fetchGetHTTP(url, flags);
    if (f == NULL) {
        if (do_cache) {
            fetchFreeURLList(&cache->ue);
            fetchFreeURL(cache->location);
            free(cache);
        }
        return -1;
    }

    state.url = url;
    state.state = ST_NONE;
    if (do_cache) {
        state.ue = &cache->ue;
    } else {
        state.ue = ue;
    }

    buf_len = 0;

    while ((read_len = fetchIO_read(f, buf + buf_len, sizeof(buf) - buf_len)) >
           0) {
        buf_len += read_len;
        sum_processed = 0;
        do {
            processed = parse_index(&state, buf + sum_processed, buf_len);
            if (processed == -1)
                break;
            buf_len -= processed;
            sum_processed += processed;
        } while (processed != 0 && buf_len > 0);
        if (processed == -1) {
            read_len = -1;
            break;
        }
        memmove(buf, buf + sum_processed, buf_len);
    }

    fetchIO_close(f);

    ret = read_len < 0 ? -1 : 0;

    if (do_cache) {
        if (ret == 0) {
            cache->next = index_cache;
            index_cache = cache;
        }

        if (fetchAppendURLList(ue, &cache->ue))
            ret = -1;
    }

    return ret;
}
