/* Copyright 2020 Jaakko Keränen <jaakko.keranen@iki.fi>

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.
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.

THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "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 COPYRIGHT OWNER OR CONTRIBUTORS 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 "mimehooks.h"
#include "defs.h"
#include "gmutil.h"
#include "gempub.h"
#include "app.h"

#include <the_Foundation/file.h>
#include <the_Foundation/fileinfo.h>
#include <the_Foundation/path.h>
#include <the_Foundation/process.h>
#include <the_Foundation/stringlist.h>
#include <the_Foundation/xml.h>

iDefineTypeConstruction(FilterHook)

void init_FilterHook(iFilterHook *d) {
    init_String(&d->label);
    init_String(&d->mimePattern);
    init_String(&d->command);
    d->mimeRegex = NULL;
}

void deinit_FilterHook(iFilterHook *d) {
    iRelease(d->mimeRegex);
    deinit_String(&d->command);
    deinit_String(&d->mimePattern);
    deinit_String(&d->label);
}

void setMimePattern_FilterHook(iFilterHook *d, const iString *pattern) {
    iReleasePtr(&d->mimeRegex);
    set_String(&d->mimePattern, pattern);
    d->mimeRegex = new_RegExp(cstr_String(pattern), caseInsensitive_RegExpOption);
}

void setCommand_FilterHook(iFilterHook *d, const iString *command) {
    set_String(&d->command, command);
}

iBlock *run_FilterHook_(const iFilterHook *d, const iString *mime, const iBlock *body,
                        const iString *requestUrl) {
    static iMutex *mtx_;
    if (!mtx_) {
        /* Currently we are starting child processes from multiple background threads.
           This is apparently not a great idea when the processes are created as forks.
           What we _should_ probably be doing is using a single dedicated thread to
           launch the child processes, via a queue of some sort, and wait for the output
           to be returned via a Condition. For now, we will avoid concurrency problems
           (mostly related to I/O pipe fds getting confused) by only running a single
           filter process at a time. */
        mtx_ = new_Mutex();
    }
    iStringList *args = new_StringList();
    iRangecc     seg  = iNullRange;
    while (nextSplit_Rangecc(range_String(&d->command), ";", &seg)) {
        pushBackRange_StringList(args, seg);
    }
    seg = iNullRange;
    while (nextSplit_Rangecc(range_String(mime), ";", &seg)) {
        pushBackRange_StringList(args, seg);
    }    
    lock_Mutex(mtx_);
    iBlock *output = NULL;
    for (int attempts = 0; attempts < 3; attempts++) {
        iProcess *proc = new_Process();
        setArguments_Process(proc, args);
        if (!isEmpty_String(requestUrl)) {
            setEnvironment_Process(
                proc,
                iClob(newStrings_StringList(
                    collectNewFormat_String("REQUEST_URL=%s", cstr_String(requestUrl)), NULL)));
        }
        if (start_Process(proc)) {
            writeInput_Process(proc, body);
            output = readOutputUntilClosed_Process(proc);
            if (!startsWith_Rangecc(range_Block(output), "20")) {
                /* Didn't produce valid output. */
                delete_Block(output);
                output = NULL;
            }
            iRelease(proc);
            break;
        }
        iRelease(proc);
    }
    unlock_Mutex(mtx_);
    iRelease(args);
    return output;
}

/*----------------------------------------------------------------------------------------------*/

static iRegExp *xmlMimePattern_(void) {
    static iRegExp *xmlMime_;
    if (!xmlMime_) {
        xmlMime_ = new_RegExp("(application|text)/(atom\\+)?xml", caseInsensitive_RegExpOption);
    }
    return xmlMime_;
}

static iBlock *translateAtomXmlToGeminiFeed_(const iString *mime, const iBlock *source,
                                             const iString *requestUrl) {
    iUnused(requestUrl); /* TODO: Use for what? */
    iRegExpMatch m;
    init_RegExpMatch(&m);
    if (!matchString_RegExp(xmlMimePattern_(), mime, &m)) {
        return NULL;
    }
    iBlock *      output = NULL;
    iXmlDocument *doc    = new_XmlDocument();
    iString       src;
    initBlock_String(&src, source); /* assume it's UTF-8 */
    if (!parse_XmlDocument(doc, &src)) {
        goto finished;
    }
    const iXmlElement *feed = &doc->root;
    if (!equal_Rangecc(feed->name, "feed")) {
        goto finished;
    }
    if (!equal_Rangecc(attribute_XmlElement(feed, "xmlns"), "http://www.w3.org/2005/Atom")) {
        goto finished;
    }
    iString *title = collect_String(decodedContent_XmlElement(child_XmlElement(feed, "title")));
    if (isEmpty_String(title)) {
        goto finished;
    }
    iString *subtitle = collect_String(decodedContent_XmlElement(child_XmlElement(feed, "subtitle")));
    iString out;
    init_String(&out);
    format_String(&out,
                  "20 text/gemini\r\n"
                  "# %s\n\n",
                  cstr_String(title));
    if (!isEmpty_String(subtitle)) {
        appendFormat_String(&out, "## %s\n\n", cstr_String(subtitle));
    }
    appendCStr_String(&out, cstr_Lang("feeds.atom.translated"));
    appendCStr_String(&out, "\n\n");
    iRegExp *datePattern =
        iClob(new_RegExp("^\\s*([0-9][0-9][0-9][0-9]-[0-1][0-9]-[0-3][0-9])(T|\\s).*",
                         caseSensitive_RegExpOption));
    iBeginCollect();
    iConstForEach(PtrArray, i, &feed->children) {
        iEndCollect();
        iBeginCollect();
        const iXmlElement *entry = i.ptr;
        if (!equal_Rangecc(entry->name, "entry")) {
            continue;
        }
        title = collect_String(decodedContent_XmlElement(child_XmlElement(entry, "title")));
        if (isEmpty_String(title)) {
            continue;
        }
        const iString *published =
            collect_String(decodedContent_XmlElement(child_XmlElement(entry, "published")));
        const iString *updated =
            collect_String(decodedContent_XmlElement(child_XmlElement(entry, "updated")));
        iRegExpMatch m;
        init_RegExpMatch(&m);
        if (!matchString_RegExp(datePattern, updated, &m)) {
            init_RegExpMatch(&m);
            if (!matchString_RegExp(datePattern, published, &m)) {
                continue;
            }
        }
        iRangecc url = iNullRange;
        iConstForEach(PtrArray, j, &entry->children) {
            const iXmlElement *link = j.ptr;
            if (!equal_Rangecc(link->name, "link")) {
                continue;
            }
            const iRangecc href = attribute_XmlElement(link, "href");
            const iRangecc rel  = attribute_XmlElement(link, "rel");
            const iRangecc type = attribute_XmlElement(link, "type");
            if (startsWithCase_Rangecc(href, "gemini:")) {
                url = href;
                /* We're happy with the first gemini URL. */
                /* TODO: Are we? */
                break;
            }
            url = href;
            iUnused(rel, type);
        }
        if (isEmpty_Range(&url)) {
            continue;
        }
        appendFormat_String(&out, "=> %s %s - %s\n",
                            cstr_Rangecc(url),
                            cstr_Rangecc(capturedRange_RegExpMatch(&m, 1)),
                            cstr_String(title));
    }
    iEndCollect();
    output = copy_Block(utf8_String(&out));
    deinit_String(&out);
finished:
    delete_XmlDocument(doc);
    deinit_String(&src);
    return output;
}

iBlock *translateGemPubCoverPage_(const iBlock *source, const iString *requestUrl) {
    iBlock *output = NULL;
    iGempub *gempub = new_Gempub();
    if (open_Gempub(gempub, source)) {
        setBaseUrl_Gempub(gempub, requestUrl);
        output = newCStr_Block("20 text/gemini; charset=utf-8\r\n");
        iString *src = coverPageSource_Gempub(gempub);
        append_Block(output, utf8_String(src));
        delete_String(src);
    }
    delete_Gempub(gempub);
    return output;
}

/*----------------------------------------------------------------------------------------------*/

static const char *mimeHooksFilename_MimeHooks_ = "mimehooks.txt";

struct Impl_MimeHooks {
    iPtrArray filters;
};

iDefineTypeConstruction(MimeHooks)

void init_MimeHooks(iMimeHooks *d) {
    init_PtrArray(&d->filters);
}

void deinit_MimeHooks(iMimeHooks *d) {
    iForEach(PtrArray, i, &d->filters) {
        delete_FilterHook(i.ptr);
    }
    deinit_PtrArray(&d->filters);
}

static iBool checkGemPub_(const iString *mime, const iString *requestUrl) {
    /* Only process GemPub in local files. */
    return (equalCase_Rangecc(urlScheme_String(requestUrl), "file") &&
            startsWithCase_String(mime, mimeType_Gempub));
}

iBool willTryFilter_MimeHooks(const iMimeHooks *d, const iString *mime) {
    /* TODO: Combine this function with tryFilter_MimeHooks! */
    iRegExpMatch m;
    iConstForEach(PtrArray, i, &d->filters) {
        const iFilterHook *xc = i.ptr;
        init_RegExpMatch(&m);
        if (matchString_RegExp(xc->mimeRegex, mime, &m)) {
            return iTrue;
        }
    }
    /* Built-in filters. */
    init_RegExpMatch(&m);
    if (matchString_RegExp(xmlMimePattern_(), mime, &m)) {
        return iTrue;
    }
    return iFalse;
}

iBlock *tryFilter_MimeHooks(const iMimeHooks *d, const iString *mime, const iBlock *body,
                            const iString *requestUrl) {
    iRegExpMatch m;
    iConstForEach(PtrArray, i, &d->filters) {
        const iFilterHook *xc = i.ptr;
        init_RegExpMatch(&m);
        if (matchString_RegExp(xc->mimeRegex, mime, &m)) {
            iBlock *result = run_FilterHook_(xc, mime, body, requestUrl);
            if (result) {
                return result;
            }
        }
    }
    /* Built-in filters. */
    if (checkGemPub_(mime, requestUrl)) {
        iBlock *result = translateGemPubCoverPage_(body, requestUrl);
        if (result) {
            return result;
        }
    }
    init_RegExpMatch(&m);
    if (matchString_RegExp(xmlMimePattern_(), mime, &m)) {
        iBlock *result = translateAtomXmlToGeminiFeed_(mime, body, requestUrl);
        if (result) {
            return result;
        }
    }
    return NULL;
}

void load_MimeHooks(iMimeHooks *d, const char *saveDir) {
    iBool reportError = iFalse;
    iFile *f = newCStr_File(concatPath_CStr(saveDir, mimeHooksFilename_MimeHooks_));
    if (open_File(f, read_FileMode | text_FileMode)) {
        iBlock * src     = readAll_File(f);
        iRangecc srcLine = iNullRange;
        int      pos     = 0;
        iRangecc lines[3];
        iZap(lines);
        while (nextSplit_Rangecc(range_Block(src), "\n", &srcLine)) {
            iRangecc line = srcLine;
            trim_Rangecc(&line);
            if (isEmpty_Range(&line)) {
                continue;
            }
            lines[pos++] = line;
            if (pos == 3) {
                iFilterHook *hook = new_FilterHook();
                setRange_String(&hook->label, lines[0]);
                setMimePattern_FilterHook(hook, collect_String(newRange_String(lines[1])));
                setCommand_FilterHook(hook, collect_String(newRange_String(lines[2])));
                /* Check if commmand is valid. */ {
                    iRangecc seg = iNullRange;
                    while (nextSplit_Rangecc(range_String(&hook->command), ";", &seg)) {
                        if (!fileExistsCStr_FileInfo(cstr_Rangecc(seg))) {
                            reportError = iTrue;
                        }
                        break;
                    }
                }
                pushBack_PtrArray(&d->filters, hook);
                pos = 0;
            }
        }
        delete_Block(src);
    }
    iRelease(f);
    if (reportError) {
        postCommand_App("~config.error where:mimehooks.txt");
    }
}

void save_MimeHooks(const iMimeHooks *d) {
    iUnused(d);
}

const iString *debugInfo_MimeHooks(const iMimeHooks *d) {
    iString *str = collectNew_String();
    size_t index = 0;
    iConstForEach(PtrArray, i, &d->filters) {
        const iFilterHook *filter = i.ptr;
        appendFormat_String(str, "### %d: %s\n", index, cstr_String(&filter->label));
        appendFormat_String(str, "MIME regex:\n```\n%s\n```\n", cstr_String(&filter->mimePattern));
        iStringList *args = iClob(split_String(&filter->command, ";"));
        if (isEmpty_StringList(args)) {
            appendFormat_String(str, "\u26a0 Command not specified!\n");
            continue;
        }
        const iString *exec = constAt_StringList(args, 0);
        if (isEmpty_String(exec)) {
            appendFormat_String(str, "\u26a0 Command not specified!\n");
        }
        else {
            appendFormat_String(str, "Executable: %s\n```\n%s\n```\n",
                                fileExists_FileInfo(exec) ? "" : "\u26a0 FILE NOT FOUND",
                                cstr_String(exec));
        }
        index++;
    }
    return str;
}