/** \file history.c
	History functions, part of the user interface.
*/
#include "config.h"

#include <stdlib.h>
#include <stdio.h>
#include <wchar.h>
#include <errno.h>
#include <dirent.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <sys/mman.h>
#include <fcntl.h>
#include <string.h>
#include <time.h>
#include <assert.h>

#include "fallback.h"
#include "util.h"
#include "sanity.h"
#include "tokenizer.h"

#include "wutil.h"
#include "history.h"
#include "common.h"
#include "intern.h"
#include "path.h"
#include "signal.h"
#include "autoload.h"
#include "iothread.h"
#include <map>
#include <algorithm>

/*

Our history format is intended to be valid YAML. Here it is:

  - cmd: ssh blah blah blah
    when: 2348237
    paths:
      - /path/to/something
      - /path/to/something_else
    
  Newlines are replaced by \n. Backslashes are replaced by \\.
*/



/** When we rewrite the history, the number of items we keep */
#define HISTORY_SAVE_MAX (1024 * 256)

/** Interval in seconds between automatic history save */
#define SAVE_INTERVAL (5*60)

/** Number of new history entries to add before automatic history save */
#define SAVE_COUNT 5

/* Our LRU cache is used for restricting the amount of history we have, and limiting how long we order it. */
class history_lru_node_t : public lru_node_t {
    public:
    time_t timestamp;
    path_list_t required_paths;
    history_lru_node_t(const history_item_t &item) :
        lru_node_t(item.str()),
        timestamp(item.timestamp()),
        required_paths(item.required_paths)
    {}
    
    bool write_to_file(FILE *f) const;
    bool write_yaml_to_file(FILE *f) const;
};

class history_lru_cache_t : public lru_cache_t<history_lru_node_t> {
    protected:
    
    /* Override to delete evicted nodes */
    virtual void node_was_evicted(history_lru_node_t *node) {
        delete node;
    }

    public:
    history_lru_cache_t(size_t max) : lru_cache_t<history_lru_node_t>(max) { }
    
    /* Function to add a history item */
    void add_item(const history_item_t &item) {
        /* Skip empty items */
        if (item.empty())
            return;
            
        /* See if it's in the cache. If it is, update the timestamp. If not, we create a new node and add it. Note that calling get_node promotes the node to the front. */
        history_lru_node_t *node = this->get_node(item.str());
        if (node != NULL) {
            node->timestamp = std::max(node->timestamp, item.timestamp());
            /* What to do about paths here? Let's just ignore them */
        } else {
            node = new history_lru_node_t(item);
            this->add_node(node);
        }
    }
};

static pthread_mutex_t hist_lock = PTHREAD_MUTEX_INITIALIZER;

static std::map<wcstring, history_t *> histories;

static wcstring history_filename(const wcstring &name, const wcstring &suffix);

/** Replaces newlines with a literal backslash followed by an n, and replaces backslashes with two backslashes. */
static void escape_yaml(std::string &str);

/** Undoes escape_yaml */
static void unescape_yaml(std::string &str);

/* Custom deleter for our shared_ptr */
class history_item_data_deleter_t {
    private:
        const bool free_it;
    public:
    history_item_data_deleter_t(bool flag) : free_it(flag) { }
    void operator()(const wchar_t *data) {
        if (free_it)
            free((void *)data);
    }
};

history_item_t::history_item_t(const wcstring &str) : contents(str), creation_timestamp(time(NULL))
{
}

history_item_t::history_item_t(const wcstring &str, time_t when, const path_list_t &paths) : contents(str), creation_timestamp(when), required_paths(paths)
{
}

bool history_item_t::matches_search(const wcstring &term, enum history_search_type_t type) const {
    switch (type) {
    
        case HISTORY_SEARCH_TYPE_CONTAINS:
        /* We consider equal strings to NOT match a contains search (so that you don't have to see history equal to what you typed). The length check ensures that. */
            return contents.size() > term.size() && contents.find(term) != wcstring::npos;
            
        case HISTORY_SEARCH_TYPE_PREFIX:
            /* We consider equal strings to match a prefix search, so that autosuggest will allow suggesting what you've typed */
            return string_prefixes_string(term, contents);
            
        default:
            sanity_lose();
            return false;
    }
}

/* Output our YAML to a file */
bool history_lru_node_t::write_yaml_to_file(FILE *f) const {
    std::string cmd = wcs2string(key);
    escape_yaml(cmd);
    if (fprintf(f, "- cmd: %s\n", cmd.c_str()) < 0)
        return false;
        
    if (fprintf(f, "   when: %ld\n", (long)timestamp) < 0)
        return false;
    
    if (! required_paths.empty()) {
        if (fputs("   paths:\n", f) < 0)
            return false;
            
        for (path_list_t::const_iterator iter = required_paths.begin(); iter != required_paths.end(); iter++) {
            std::string path = wcs2string(*iter);
            escape_yaml(path);
            
            if (fprintf(f, "    - %s\n", path.c_str()) < 0)
                return false;
        }
    }
    return true;
}

history_t & history_t::history_with_name(const wcstring &name) {
    /* Note that histories are currently never deleted, so we can return a reference to them without using something like shared_ptr */
    scoped_lock locker(hist_lock);
    history_t *& current = histories[name];
    if (current == NULL)
        current = new history_t(name);
    return *current;
}

history_t::history_t(const wcstring &pname) :
    name(pname),
    mmap_start(NULL),
    mmap_length(0),
    save_timestamp(0),
    loaded_old(false)
{
    pthread_mutex_init(&lock, NULL);
}

history_t::~history_t()
{
    pthread_mutex_destroy(&lock);
}

void history_t::add(const history_item_t &item)
{
    scoped_lock locker(lock);
    
    /* Add the history items */
    new_items.push_back(item);
    
    /* Prevent the first write from always triggering a save */
    time_t now = time(NULL);
    if (! save_timestamp)
        save_timestamp = now;
    
    /* This might be a good candidate for moving to a background thread */
    if((now > save_timestamp + SAVE_INTERVAL) || (new_items.size() >= SAVE_COUNT))
		this->save_internal();

}

void history_t::add(const wcstring &str, const path_list_t &valid_paths)
{
    this->add(history_item_t(str, time(NULL), valid_paths));
}

history_item_t history_t::item_at_index(size_t idx) {
    scoped_lock locker(lock);
    
    /* 0 is considered an invalid index */
    assert(idx > 0);
    idx--;
    
    /* idx=0 corresponds to last item in new_items */
    size_t new_item_count = new_items.size();
    if (idx < new_item_count) {
        return new_items.at(new_item_count - idx - 1);
    }
    
    /* Now look in our old items */
    idx -= new_item_count;
    load_old_if_needed();
    size_t old_item_count = old_item_offsets.size();
    if (idx < old_item_count) {
        /* idx=0 corresponds to last item in old_item_offsets */
        size_t offset = old_item_offsets.at(old_item_count - idx - 1);
        return history_t::decode_item(mmap_start + offset, mmap_length - offset);
    }
    
    /* Index past the valid range, so return an empty history item */
    return history_item_t(wcstring(), 0);
}

/* Read one line, stripping off any newline, and updating cursor. Note that our string is NOT null terminated; it's just a memory mapped file. */
static size_t read_line(const char *base, size_t cursor, size_t len, std::string &result) {
    /* Locate the newline */
    assert(cursor <= len);
    const char *start = base + cursor;
    const char *newline = (char *)memchr(start, '\n', len - cursor);
    if (newline != NULL) {
        /* We found a newline. */
        result.assign(start, newline - start);
        
        /* Return the amount to advance the cursor; skip over the newline */
        return newline - start + 1;
    } else {
        /* We ran off the end */
        result.clear();
        return len - cursor;
    }
}

/* Trims leading spaces in the given string, returning how many there were */
static size_t trim_leading_spaces(std::string &str) {
    size_t i = 0, max = str.size();
    while (i < max && str[i] == ' ')
        i++;
    str.erase(0, i);
    return i;
}

static bool extract_prefix(std::string &key, std::string &value, const std::string &line) {
    size_t where = line.find(":");
    if (where != std::string::npos) {
        key = line.substr(0, where);
        
        // skip a space after the : if necessary
        size_t val_start = where + 1;
        if (val_start < line.size() && line.at(val_start) == ' ')
            val_start++;
        value = line.substr(val_start);
    }
    return where != std::string::npos;
}

history_item_t history_t::decode_item(const char *base, size_t len) {
    wcstring cmd;
    time_t when = 0;
    path_list_t paths;
    
    size_t indent = 0, cursor = 0;
    std::string key, value, line;
    
    /* Read the "- cmd:" line */
    size_t advance = read_line(base, cursor, len, line);
    trim_leading_spaces(line);
    if (! extract_prefix(key, value, line) || key != "- cmd")
        goto done;
    
    cursor += advance;
    cmd = str2wcstring(value);

    /* Read the remaining lines */
    for (;;) {
        /* Read a line */
        size_t advance = read_line(base, cursor, len, line);
        
        /* Count and trim leading spaces */
        size_t this_indent = trim_leading_spaces(line);
        if (indent == 0)
            indent = this_indent;
        
        if (this_indent == 0 || indent != this_indent)
            break;
        
        if (! extract_prefix(key, value, line))
            break;
            
        /* We are definitely going to consume this line */
        unescape_yaml(value);
        cursor += advance;
        
        if (key == "when") {
            /* Parse an int from the timestamp */
            long tmp = 0;
            if (sscanf(value.c_str(), "%ld", &tmp) > 0) {
                when = tmp;
            }
        } else if (key == "paths") {
            /* Read lines starting with " - " until we can't read any more */
            for (;;) {
                size_t advance = read_line(base, cursor, len, line);
                if (trim_leading_spaces(line) <= indent)
                    break;
                    
                if (strncmp(line.c_str(), "- ", 2))
                    break;
                    
                /* We're going to consume this line */
                cursor += advance;
                

                /* Skip the leading dash-space and then store this path it */
                line.erase(0, 2);
                unescape_yaml(line);
                paths.push_front(str2wcstring(line));
            }
        }
    }
    /* Reverse the paths, since we pushed them to the front each time */
done:
    paths.reverse();
    return history_item_t(cmd, when, paths);
    
}

void history_t::populate_from_mmap(void)
{
	const char *begin = mmap_start;
    size_t cursor = 0;
    while (cursor < mmap_length) {
        const char *line_start = begin + cursor;
        /* Look for a newline */
        const char *newline = (const char *)memchr(line_start, '\n', mmap_length - cursor);
        if (newline == NULL)
            break;
        
        /* Advance the cursor past this line. +1 is for the newline */
        size_t line_len = newline - line_start;
        cursor += line_len + 1;

        /* Skip lines with a leading, since these are in the interior of one of our items */
        if (line_start[0] == ' ')
            continue;
        
        /* Skip very short lines to make one of the checks below easier */
        if (line_len < 3)
            continue;
        
        /* Try to be a little YAML compatible. Skip lines with leading %, ---, or ... */
        if (! memcmp(line_start, "%", 1) ||
            ! memcmp(line_start, "---", 3) ||
            ! memcmp(line_start, "...", 3))
            continue;
            
        /* We made it through the gauntlet. */
        old_item_offsets.push_back(line_start - begin);
    }
}

void history_t::load_old_if_needed(void)
{
    if (loaded_old) return;
    loaded_old = true;
    
	int fd;
	int ok=0;
	
	signal_block();
    wcstring filename = history_filename(name, L"");
	
	if( ! filename.empty() )
	{
		if( ( fd = wopen( filename, O_RDONLY ) ) > 0 )
		{
			off_t len = lseek( fd, 0, SEEK_END );
			if( len != (off_t)-1)
			{
				mmap_length = (size_t)len;
				if( lseek( fd, 0, SEEK_SET ) == 0 )
				{
					if( (mmap_start = (char *)mmap( 0, mmap_length, PROT_READ, MAP_PRIVATE, fd, 0 )) != MAP_FAILED )
					{
						ok = 1;
						this->populate_from_mmap();
					}
				}
			}
			close( fd );
		}
	}
	signal_unblock();
}

void history_search_t::skip_matches(const wcstring_list_t &skips) {
    external_skips = skips;
    std::sort(external_skips.begin(), external_skips.end());
}

bool history_search_t::should_skip_match(const wcstring &str) const {
    return std::binary_search(external_skips.begin(), external_skips.end(), str);
}

bool history_search_t::go_forwards() {
    /* Pop the top index (if more than one) and return if we have any left */
    if (prev_matches.size() > 1) {
        prev_matches.pop_back();
        return true;
    }
    return false;
}

bool history_search_t::go_backwards() {
    /* Backwards means increasing our index */
    const size_t max_idx = (size_t)(-1);

    size_t idx = 0;
    if (! prev_matches.empty())
        idx = prev_matches.back().first;
    
    if (idx == max_idx)
        return false;
        
    while (++idx < max_idx) {
        const history_item_t item = history->item_at_index(idx);
        /* We're done if it's empty */
        if (item.empty()) {
            return false;
        }

        /* Look for a term that matches and that we haven't seen before */
        const wcstring &str = item.str();
        if (item.matches_search(term, search_type) && ! match_already_made(str) && ! should_skip_match(str)) {
            prev_matches.push_back(prev_match_t(idx, item));
            return true;
        }
    }
    return false;
}

/** Goes to the end (forwards) */
void history_search_t::go_to_end(void) {
    prev_matches.clear();
}

/** Returns if we are at the end, which is where we start. */
bool history_search_t::is_at_end(void) const {
    return prev_matches.empty();
}


/** Goes to the beginning (backwards) */
void history_search_t::go_to_beginning(void) {
    /* Just go backwards as far as we can */
    while (go_backwards())
        ;
}


history_item_t history_search_t::current_item() const {
    assert(! prev_matches.empty()); 
    return prev_matches.back().second;
}

wcstring history_search_t::current_string() const {
    history_item_t item = this->current_item();
    return item.str();
}

bool history_search_t::match_already_made(const wcstring &match) const {
    for (std::deque<prev_match_t>::const_iterator iter = prev_matches.begin(); iter != prev_matches.end(); iter++) {
        if (iter->second.str() == match)
            return true;
    }
    return false;
}

static void replace_all(std::string &str, const char *needle, const char *replacement)
{
    size_t needle_len = strlen(needle), replacement_len = strlen(replacement);
    size_t offset = 0;
    while((offset = str.find(needle, offset)) != std::string::npos)
    {
        str.replace(offset, needle_len, replacement);
        offset += replacement_len;
    }
}

static void escape_yaml(std::string &str) {
    replace_all(str, "\\", "\\\\"); //replace one backslash with two
    replace_all(str, "\n", "\\n"); //replace newline with backslash + literal n
}

static void unescape_yaml(std::string &str) {
    bool prev_escape = false;
    for (size_t idx = 0; idx < str.size(); idx++) {
        char c = str.at(idx);
        if (prev_escape) {
            if (c == '\\') {
                /* Two backslashes in a row. Delete this one */
                str.erase(idx, 1);
                idx--;
            } else if (c == 'n') {
                /* Replace backslash + n with an actual newline */
                str.replace(idx - 1, 2, "\n");
                idx--;
            }
            prev_escape = false;
        } else {
            prev_escape = (c == '\\');
        }
    }
}

static wcstring history_filename(const wcstring &name, const wcstring &suffix)
{
    wcstring path;
    if (! path_get_config(path))
        return L"";
    
    wcstring result = path;
    result.append(L"/");
    result.append(name);
    result.append(L"_history");
    result.append(suffix);
    return result;
}

void history_t::clear_file_state()
{
    /* Erase everything we know about our file */
    if (mmap_start != NULL && mmap_start != MAP_FAILED) {
        munmap((void *)mmap_start, mmap_length);
    }
    mmap_start = 0;
    mmap_length = 0;
    loaded_old = false;
    new_items.clear();
    old_item_offsets.clear();
    save_timestamp=time(0);
}

/** Save the specified mode to file */
void history_t::save_internal()
{
    /* This must be called while locked */
    
    /* Nothing to do if there's no new items */
    if (new_items.empty())
        return;
    
	bool ok = true;
	
	signal_block();
    
    wcstring tmp_name = history_filename(name, L".tmp");
	if( ! tmp_name.empty() )
	{
        FILE *out;
		if( (out=wfopen( tmp_name, "w" ) ) )
		{
                
            /* Load old */
            load_old_if_needed();
            
            /* Make an LRU cache to save only the last N elements */
            history_lru_cache_t lru(HISTORY_SAVE_MAX);
            
            /* Insert old items in, from old to new */
            for (std::deque<size_t>::iterator iter = old_item_offsets.begin(); iter != old_item_offsets.end(); iter++) {
                size_t offset = *iter;
                history_item_t item = history_t::decode_item(mmap_start + offset, mmap_length - offset);
                lru.add_item(item);
            }
            
            /* Insert new items */
            for (std::vector<history_item_t>::iterator iter = new_items.begin(); iter != new_items.end(); iter++) {
                lru.add_item(*iter);
            }
            
            /* Write them out */
            for (history_lru_cache_t::iterator iter = lru.begin(); iter != lru.end(); iter++) {
                const history_lru_node_t *node = *iter;
                if (! node->write_yaml_to_file(out)) {
                    ok = false;
                    break;
                }
            }
            
            /* Make sure we clear all nodes, since this doesn't happen automatically */
            lru.evict_all_nodes();

			if( fclose( out ) || !ok )
			{
				/*
				  This message does not have high enough priority to
				  be shown by default.
				*/
				debug( 2, L"Error when writing history file" );
			}
			else
			{
                wcstring new_name = history_filename(name, wcstring());
				wrename(tmp_name, new_name);
			}
		}
	}	

	if( ok )
	{
		/* Our history has been written to the file, so clear our state so we can re-reference the file. */
		this->clear_file_state();
	}
	
	signal_unblock();
}

void history_t::save(void) {
    scoped_lock locker(lock);
    this->save_internal();
}

void history_t::clear(void) {
    scoped_lock locker(lock);
    new_items.clear();
    old_item_offsets.clear();
    wcstring filename = history_filename(name, L"");
    if (! filename.empty())
        wunlink(filename);
    this->clear_file_state();
    
}

void history_init()
{
}


void history_destroy()
{
    /* Save all histories */
    for (std::map<wcstring, history_t *>::iterator iter = histories.begin(); iter != histories.end(); iter++) {
        iter->second->save();
    }
}


void history_sanity_check()
{
	/*
	  No sanity checking implemented yet...
	*/
}

int file_detection_context_t::perform_file_detection(bool test_all) {
    ASSERT_IS_BACKGROUND_THREAD();
    valid_paths.clear();
    int result = 1;
    for (path_list_t::const_iterator iter = potential_paths.begin(); iter != potential_paths.end(); iter++) {    
        if (path_is_valid(*iter, working_directory)) {
            /* Push the original (possibly relative) path */
            valid_paths.push_front(*iter);
        } else {
            /* Not a valid path */
            result = 0;
            if (! test_all)
                break;
        }
    }
    valid_paths.reverse();
    return result;
}

bool file_detection_context_t::paths_are_valid(const path_list_t &paths) {
    this->potential_paths = paths;
    return perform_file_detection(false) > 0;
}

file_detection_context_t::file_detection_context_t(history_t *hist, const wcstring &cmd) :
    history(hist),
    command(cmd),
    when(time(NULL)),
    working_directory(get_working_directory())
{
}

static int threaded_perform_file_detection(file_detection_context_t *ctx) {
    ASSERT_IS_BACKGROUND_THREAD();
    assert(ctx != NULL);
    return ctx->perform_file_detection(true /* test all */);
}

static void perform_file_detection_done(file_detection_context_t *ctx, int success) {
    /* Now that file detection is done, create the history item */
    ctx->history->add(ctx->command, ctx->valid_paths);
    
    /* Done with the context. */
    delete ctx;
}

static bool string_could_be_path(const wcstring &potential_path) {
    // Assume that things with leading dashes aren't paths
    if (potential_path.empty() || potential_path.at(0) == L'-')
        return false;
    return true;
}

void history_t::add_with_file_detection(const wcstring &str)
{
    ASSERT_IS_MAIN_THREAD();
    path_list_t potential_paths;
    
    tokenizer tokenizer;
    for( tok_init( &tokenizer, str.c_str(), TOK_SQUASH_ERRORS );
        tok_has_next( &tokenizer );
        tok_next( &tokenizer ) )
    {
        int type = tok_last_type( &tokenizer );
        if (type == TOK_STRING) {
            const wchar_t *token_cstr = tok_last(&tokenizer);
            if (token_cstr) {
                wcstring potential_path = token_cstr;
                if (unescape_string(potential_path, false) && string_could_be_path(potential_path)) {
                    potential_paths.push_front(potential_path);
                }
            }
        }
    }
    
    if (! potential_paths.empty()) {
        /* We have some paths. Make a context. */
        file_detection_context_t *context = new file_detection_context_t(this, str);
                        
        /* Store the potential paths. Reverse them to put them in the same order as in the command. */
        potential_paths.reverse();
        context->potential_paths.swap(potential_paths);
        iothread_perform(threaded_perform_file_detection, perform_file_detection_done, context);
    }
}