/*
Connector to let httpd use the espfs filesystem to serve the files in it.
*/

/*
 * ----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * Jeroen Domburg <jeroen@spritesmods.com> wrote this file. As long as you retain
 * this notice you can do whatever you want with this stuff. If we meet some day,
 * and you think this stuff is worth it, you can buy me a beer in return.
 * ----------------------------------------------------------------------------
 */

#include <stddef.h>
#include <string.h>
#include "httpd.h"
#include "httpd-platform.h"
#include "httpdespfs.h"
#include "espfs.h"
#include "espfsformat.h"
#include "logging.h"

#define FILE_CHUNK_LEN 1024

// The static files marked with FLAG_GZIP are compressed and will be served with GZIP compression.
// If the client does not advertise that he accepts GZIP send following warning message (telnet users for e.g.)
static const char *gzipNonSupportedMessage = "HTTP/1.0 501 Not implemented\r\n"
                                             "Connection: close\r\n"
                                             "Content-Type: text/plain\r\n"
                                             "Content-Length: 52\r\n"
                                             "\r\n"
                                             "Your browser does not accept gzip-compressed data.\r\n";

/**
 * Try to open a file
 * @param path - path to the file, may end with slash
 * @param indexname - filename at the path
 * @return file pointer or NULL
 */
static EspFsFile *tryOpenIndex_do(const char *path, const char *indexname)
{
    char fname[100];
    size_t url_len = strlen(path);
    strncpy(fname, path, 99);

    // Append slash if missing
    if (path[url_len - 1] != '/') {
        fname[url_len++] = '/';
    }

    strcpy(fname + url_len, indexname);

    // Try to open, returns NULL if failed
    return espFsOpen(fname);
}

/**
 * Try to find index file on a path
 * @param path - directory
 * @return file pointer or NULL
 */
EspFsFile *tryOpenIndex(const char *path)
{
    EspFsFile *file;
    // A dot in the filename probably means extension
    // no point in trying to look for index.
    if (strchr(path, '.') != NULL) { return NULL; }

    file = tryOpenIndex_do(path, "index.html");
    if (file != NULL) { return file; }

    file = tryOpenIndex_do(path, "index.htm");
    if (file != NULL) { return file; }

    file = tryOpenIndex_do(path, "index.tpl.html");
    if (file != NULL) { return file; }

    file = tryOpenIndex_do(path, "index.tpl");
    if (file != NULL) { return file; }

    return NULL; // failed to guess the right name
}

httpd_cgi_state
serveStaticFile(HttpdConnData *connData, const char *filepath)
{
    EspFsFile *file = connData->cgiData;
    int len;
    uint8_t buff[FILE_CHUNK_LEN + 1];
    char acceptEncodingBuffer[64 + 1];
    int isGzip;

    if (connData->conn == NULL) {
        //Connection aborted. Clean up.
        espFsClose(file);
        return HTTPD_CGI_DONE;
    }

    // invalid call.
    if (filepath == NULL) {
        espfs_error("serveStaticFile called with NULL path!");
        return HTTPD_CGI_NOTFOUND;
    }

    //First call to this cgi.
    if (file == NULL) {
        //First call to this cgi. Open the file so we can read it.
        file = espFsOpen(filepath);
        if (file == NULL) {
            // file not found

            // If this is a folder, look for index file
            file = tryOpenIndex(filepath);
            if (file == NULL) { return HTTPD_CGI_NOTFOUND; }
        }

        // The gzip checking code is intentionally without #ifdefs because checking
        // for FLAG_GZIP (which indicates gzip compressed file) is very easy, doesn't
        // mean additional overhead and is actually safer to be on at all times.
        // If there are no gzipped files in the image, the code bellow will not cause any harm.

        // Check if requested file was GZIP compressed
        isGzip = espFsFlags(file) & FLAG_GZIP;
        if (isGzip) {
            // Check the browser's "Accept-Encoding" header. If the client does not
            // advertise that he accepts GZIP send a warning message (telnet users for e.g.)
            httpdGetHeader(connData, "Accept-Encoding", acceptEncodingBuffer, 64);
            if (strstr(acceptEncodingBuffer, "gzip") == NULL) {
                //No Accept-Encoding: gzip header present
                httpdSendStr(connData, gzipNonSupportedMessage);
                espFsClose(file);
                return HTTPD_CGI_DONE;
            }
        }

        connData->cgiData = file;
        httpdStartResponse(connData, 200);
        const char *mime = httpdGetMimetype(filepath);
        httpdHeader(connData, "Content-Type", mime);
        if (isGzip) {
            httpdHeader(connData, "Content-Encoding", "gzip");
        }
        httpdAddCacheHeaders(connData, mime);
        httpdEndHeaders(connData);
        return HTTPD_CGI_MORE;
    }

    len = espFsRead(file, buff, FILE_CHUNK_LEN);
    if (len > 0) {
        espfs_dbg("[EspFS] Read file chunk: %d bytes", len);
        httpdSend(connData, buff, len);
    }
    if (len != FILE_CHUNK_LEN) {
        //We're done.
        espFsClose(file);
        return HTTPD_CGI_DONE;
    } else {
        //Ok, till next time.
        return HTTPD_CGI_MORE;
    }
}


//This is a catch-all cgi function. It takes the url passed to it, looks up the corresponding
//path in the filesystem and if it exists, passes the file through. This simulates what a normal
//webserver would do with static files.
httpd_cgi_state cgiEspFsHook(HttpdConnData *connData)
{
    const char *filepath = (connData->cgiArg == NULL) ? connData->url : (char *) connData->cgiArg;
    return serveStaticFile(connData, filepath);
}


//cgiEspFsTemplate can be used as a template.

typedef enum {
  ENCODE_PLAIN = 0,
  ENCODE_HTML,
  ENCODE_JS,
} TplEncode;

typedef struct {
  EspFsFile *file;
  void *tplArg;
  char token[64];
  int tokenPos;

  char buff[FILE_CHUNK_LEN + 1];

  bool chunk_resume;
  int buff_len;
  int buff_x;
  int buff_sp;
  char *buff_e;
  TplEncode tokEncode;
} TplData;


int
tplSend(HttpdConnData *conn, const char *str, int len)
{
    if (conn == NULL) { return 0; }
    TplData *tpd = conn->cgiData;

    if (tpd == NULL || tpd->tokEncode == ENCODE_PLAIN) {
        return httpdSendStrN(conn, str, len);
    } else if (tpd->tokEncode == ENCODE_HTML) {
        return httpdSend_html(conn, (const uint8_t *) str, len);
    } else if (tpd->tokEncode == ENCODE_JS) {
        return httpdSend_js(conn, (const uint8_t *) str, len);
    }
    return 0;
}


httpd_cgi_state cgiEspFsTemplate(HttpdConnData *connData)
{
    TplData *tpd = connData->cgiData;
    int len;
    int x, sp = 0;
    char *e = NULL;
    int tokOfs;

    if (connData->conn == NULL) {
        //Connection aborted. Clean up.
        ((TplCallback) (connData->cgiArg))(connData, NULL, &tpd->tplArg);
        espFsClose(tpd->file);
        httpdPlatFree(tpd);
        return HTTPD_CGI_DONE;
    }

    if (tpd == NULL) {
        //First call to this cgi. Open the file so we can read it.
        tpd = (TplData *) httpdPlatMalloc(sizeof(TplData));
        if (tpd == NULL) {
            espfs_error("Failed to malloc tpl struct");
            return HTTPD_CGI_NOTFOUND;
        }

        tpd->chunk_resume = false;

        const char *filepath = connData->url;
        // check for custom template URL
        if (connData->cgiArg2 != NULL) {
            filepath = connData->cgiArg2;
            espfs_dbg("Using filepath %s", filepath);
        }

        tpd->file = espFsOpen(filepath);

        if (tpd->file == NULL) {
            // maybe a folder, look for index file
            tpd->file = tryOpenIndex(filepath);
            if (tpd->file == NULL) {
                httpdPlatFree(tpd);
                return HTTPD_CGI_NOTFOUND;
            }
        }

        tpd->tplArg = NULL;
        tpd->tokenPos = -1;
        if (espFsFlags(tpd->file) & FLAG_GZIP) {
            espfs_error("cgiEspFsTemplate: Trying to use gzip-compressed file %s as template!", connData->url);
            espFsClose(tpd->file);
            httpdPlatFree(tpd);
            return HTTPD_CGI_NOTFOUND;
        }
        connData->cgiData = tpd;
        httpdStartResponse(connData, 200);
        const char *mime = httpdGetMimetype(connData->url);
        httpdHeader(connData, "Content-Type", mime);
        httpdAddCacheHeaders(connData, mime);
        httpdEndHeaders(connData);
        return HTTPD_CGI_MORE;
    }

    char *buff = tpd->buff;

    // resume the parser state from the last token,
    // if subst. func wants more data to be sent.
    if (tpd->chunk_resume) {
        //espfs_dbg("Resuming tpl parser for multi-part subst");
        len = tpd->buff_len;
        e = tpd->buff_e;
        sp = tpd->buff_sp;
        x = tpd->buff_x;
    } else {
        len = espFsRead(tpd->file, (uint8_t *) buff, FILE_CHUNK_LEN);
        tpd->buff_len = len;

        e = buff;
        sp = 0;
        x = 0;
    }

    if (len > 0) {
        for (; x < len; x++) {
            if (tpd->tokenPos == -1) {
                //Inside ordinary text.
                if (buff[x] == '%') {
                    //Send raw data up to now
                    if (sp != 0) { httpdSendStrN(connData, e, sp); }
                    sp = 0;
                    //Go collect token chars.
                    tpd->tokenPos = 0;
                } else {
                    sp++;
                }
            } else {
                if (buff[x] == '%') {
                    if (tpd->tokenPos == 0) {
                        //This is the second % of a %% escape string.
                        //Send a single % and resume with the normal program flow.
                        httpdSendStrN(connData, "%", 1);
                    } else {
                        if (!tpd->chunk_resume) {
                            //This is an actual token.
                            tpd->token[tpd->tokenPos++] = 0; //zero-terminate token

                            tokOfs = 0;
                            tpd->tokEncode = ENCODE_PLAIN;
                            if (strneq(tpd->token, "html:", 5)) {
                                tokOfs = 5;
                                tpd->tokEncode = ENCODE_HTML;
                            } else if (strneq(tpd->token, "h:", 2)) {
                                tokOfs = 2;
                                tpd->tokEncode = ENCODE_HTML;
                            } else if (strneq(tpd->token, "js:", 3)) {
                                tokOfs = 3;
                                tpd->tokEncode = ENCODE_JS;
                            } else if (strneq(tpd->token, "j:", 2)) {
                                tokOfs = 2;
                                tpd->tokEncode = ENCODE_JS;
                            }

                            // do the shifting
                            if (tokOfs > 0) {
                                for (int i = tokOfs; i <= tpd->tokenPos; i++) {
                                    tpd->token[i - tokOfs] = tpd->token[i];
                                }
                            }
                        }

                        tpd->chunk_resume = false;

                        httpd_cgi_state status = ((TplCallback) (connData->cgiArg))(connData, tpd->token, &tpd->tplArg);
                        if (status == HTTPD_CGI_MORE) {
//							espfs_dbg("Multi-part tpl subst, saving parser state");
                            // wants to send more in this token's place.....
                            tpd->chunk_resume = true;
                            tpd->buff_len = len;
                            tpd->buff_e = e;
                            tpd->buff_sp = sp;
                            tpd->buff_x = x;
                            break;
                        }
                    }
                    //Go collect normal chars again.
                    e = &buff[x + 1];
                    tpd->tokenPos = -1;
                } else {
                    // Add char to the token buf
                    char c = buff[x];
                    bool outOfSpace = tpd->tokenPos >= (sizeof(tpd->token) - 1);
                    if (outOfSpace ||
                        (!(c >= 'a' && c <= 'z') &&
                         !(c >= 'A' && c <= 'Z') &&
                         !(c >= '0' && c <= '9') &&
                         c != '.' && c != '_' && c != '-' && c != ':'
                        )) {
                        // looks like we collected some garbage
                        httpdSendStrN(connData, "%", 1);
                        if (tpd->tokenPos > 0) {
                            httpdSendStrN(connData, tpd->token, tpd->tokenPos);
                        }
                        // the bad char
                        httpdSendStrN(connData, &c, 1);

                        //Go collect normal chars again.
                        e = &buff[x + 1];
                        tpd->tokenPos = -1;
                    } else {
                        // collect it
                        tpd->token[tpd->tokenPos++] = c;
                    }
                }
            }
        }
    }

    if (tpd->chunk_resume) {
        return HTTPD_CGI_MORE;
    }

    //Send remaining bit.
    if (sp != 0) { httpdSendStrN(connData, e, sp); }
    if (len != FILE_CHUNK_LEN) {
        //We're done.
        ((TplCallback) (connData->cgiArg))(connData, NULL, &tpd->tplArg);
        espfs_info("Template sent.");
        espFsClose(tpd->file);
        httpdPlatFree(tpd);
        return HTTPD_CGI_DONE;
    } else {
        //Ok, till next time.
        return HTTPD_CGI_MORE;
    }
}