#include "cache.h"
#include "config.h"
#include "dir.h"
#include "ewah/ewok.h"
#include "fsmonitor.h"
#include "run-command.h"
#include "strbuf.h"

#define INDEX_EXTENSION_VERSION (1)
#define HOOK_INTERFACE_VERSION  (1)

struct trace_key trace_fsmonitor = TRACE_KEY_INIT(FSMONITOR);

static void fsmonitor_ewah_callback(size_t pos, void *is)
{
        struct index_state *istate = (struct index_state *)is;
        struct cache_entry *ce = istate->cache[pos];

        ce->ce_flags &= ~CE_FSMONITOR_VALID;
}

int read_fsmonitor_extension(struct index_state *istate, const void *data,
        unsigned long sz)
{
        const char *index = data;
        uint32_t hdr_version;
        uint32_t ewah_size;
        struct ewah_bitmap *fsmonitor_dirty;
        int ret;

        if (sz < sizeof(uint32_t) + sizeof(uint64_t) + sizeof(uint32_t))
                return error("corrupt fsmonitor extension (too short)");

        hdr_version = get_be32(index);
        index += sizeof(uint32_t);
        if (hdr_version != INDEX_EXTENSION_VERSION)
                return error("bad fsmonitor version %d", hdr_version);

        istate->fsmonitor_last_update = get_be64(index);
        index += sizeof(uint64_t);

        ewah_size = get_be32(index);
        index += sizeof(uint32_t);

        fsmonitor_dirty = ewah_new();
        ret = ewah_read_mmap(fsmonitor_dirty, index, ewah_size);
        if (ret != ewah_size) {
                ewah_free(fsmonitor_dirty);
                return error("failed to parse ewah bitmap reading fsmonitor index extension");
        }
        istate->fsmonitor_dirty = fsmonitor_dirty;

        trace_printf_key(&trace_fsmonitor, "read fsmonitor extension successful");
        return 0;
}

void write_fsmonitor_extension(struct strbuf *sb, struct index_state *istate)
{
        uint32_t hdr_version;
        uint64_t tm;
        struct ewah_bitmap *bitmap;
        int i;
        uint32_t ewah_start;
        uint32_t ewah_size = 0;
        int fixup = 0;

        put_be32(&hdr_version, INDEX_EXTENSION_VERSION);
        strbuf_add(sb, &hdr_version, sizeof(uint32_t));

        put_be64(&tm, istate->fsmonitor_last_update);
        strbuf_add(sb, &tm, sizeof(uint64_t));
        fixup = sb->len;
        strbuf_add(sb, &ewah_size, sizeof(uint32_t)); /* we'll fix this up later */

        ewah_start = sb->len;
        bitmap = ewah_new();
        for (i = 0; i < istate->cache_nr; i++)
                if (!(istate->cache[i]->ce_flags & CE_FSMONITOR_VALID))
                        ewah_set(bitmap, i);
        ewah_serialize_strbuf(bitmap, sb);
        ewah_free(bitmap);

        /* fix up size field */
        put_be32(&ewah_size, sb->len - ewah_start);
        memcpy(sb->buf + fixup, &ewah_size, sizeof(uint32_t));

        trace_printf_key(&trace_fsmonitor, "write fsmonitor extension successful");
}

/*
 * Call the query-fsmonitor hook passing the time of the last saved results.
 */
static int query_fsmonitor(int version, uint64_t last_update, struct strbuf *query_result)
{
        struct child_process cp = CHILD_PROCESS_INIT;
        char ver[64];
        char date[64];
        const char *argv[4];

        if (!(argv[0] = core_fsmonitor))
                return -1;

        snprintf(ver, sizeof(version), "%d", version);
        snprintf(date, sizeof(date), "%" PRIuMAX, (uintmax_t)last_update);
        argv[1] = ver;
        argv[2] = date;
        argv[3] = NULL;
        cp.argv = argv;
        cp.use_shell = 1;
        cp.dir = get_git_work_tree();

        return capture_command(&cp, query_result, 1024);
}

static void fsmonitor_refresh_callback(struct index_state *istate, const char *name)
{
        int pos = index_name_pos(istate, name, strlen(name));

        if (pos >= 0) {
                struct cache_entry *ce = istate->cache[pos];
                ce->ce_flags &= ~CE_FSMONITOR_VALID;
        }

        /*
         * Mark the untracked cache dirty even if it wasn't found in the index
         * as it could be a new untracked file.
         */
        trace_printf_key(&trace_fsmonitor, "fsmonitor_refresh_callback '%s'", name);
        untracked_cache_invalidate_path(istate, name);
}

void refresh_fsmonitor(struct index_state *istate)
{
        static int has_run_once = 0;
        struct strbuf query_result = STRBUF_INIT;
        int query_success = 0;
        size_t bol; /* beginning of line */
        uint64_t last_update;
        char *buf;
        int i;

        if (!core_fsmonitor || has_run_once)
                return;
        has_run_once = 1;

        trace_printf_key(&trace_fsmonitor, "refresh fsmonitor");
        /*
         * This could be racy so save the date/time now and query_fsmonitor
         * should be inclusive to ensure we don't miss potential changes.
         */
        last_update = getnanotime();

        /*
         * If we have a last update time, call query_fsmonitor for the set of
         * changes since that time, else assume everything is possibly dirty
         * and check it all.
         */
        if (istate->fsmonitor_last_update) {
                query_success = !query_fsmonitor(HOOK_INTERFACE_VERSION,
                        istate->fsmonitor_last_update, &query_result);
                trace_performance_since(last_update, "fsmonitor process '%s'", core_fsmonitor);
                trace_printf_key(&trace_fsmonitor, "fsmonitor process '%s' returned %s",
                        core_fsmonitor, query_success ? "success" : "failure");
        }

        /* a fsmonitor process can return '/' to indicate all entries are invalid */
        if (query_success && query_result.buf[0] != '/') {
                /* Mark all entries returned by the monitor as dirty */
                buf = query_result.buf;
                bol = 0;
                for (i = 0; i < query_result.len; i++) {
                        if (buf[i] != '\0')
                                continue;
                        fsmonitor_refresh_callback(istate, buf + bol);
                        bol = i + 1;
                }
                if (bol < query_result.len)
                        fsmonitor_refresh_callback(istate, buf + bol);
        } else {
                /* Mark all entries invalid */
                for (i = 0; i < istate->cache_nr; i++)
                        istate->cache[i]->ce_flags &= ~CE_FSMONITOR_VALID;

                if (istate->untracked)
                        istate->untracked->use_fsmonitor = 0;
        }
        strbuf_release(&query_result);

        /* Now that we've updated istate, save the last_update time */
        istate->fsmonitor_last_update = last_update;
}

void add_fsmonitor(struct index_state *istate)
{
        int i;

        if (!istate->fsmonitor_last_update) {
                trace_printf_key(&trace_fsmonitor, "add fsmonitor");
                istate->cache_changed |= FSMONITOR_CHANGED;
                istate->fsmonitor_last_update = getnanotime();

                /* reset the fsmonitor state */
                for (i = 0; i < istate->cache_nr; i++)
                        istate->cache[i]->ce_flags &= ~CE_FSMONITOR_VALID;

                /* reset the untracked cache */
                if (istate->untracked) {
                        add_untracked_cache(istate);
                        istate->untracked->use_fsmonitor = 1;
                }

                /* Update the fsmonitor state */
                refresh_fsmonitor(istate);
        }
}

void remove_fsmonitor(struct index_state *istate)
{
        if (istate->fsmonitor_last_update) {
                trace_printf_key(&trace_fsmonitor, "remove fsmonitor");
                istate->cache_changed |= FSMONITOR_CHANGED;
                istate->fsmonitor_last_update = 0;
        }
}

void tweak_fsmonitor(struct index_state *istate)
{
        int i;
        int fsmonitor_enabled = git_config_get_fsmonitor();

        if (istate->fsmonitor_dirty) {
                if (fsmonitor_enabled) {
                        /* Mark all entries valid */
                        for (i = 0; i < istate->cache_nr; i++) {
                                istate->cache[i]->ce_flags |= CE_FSMONITOR_VALID;
                        }

                        /* Mark all previously saved entries as dirty */
                        ewah_each_bit(istate->fsmonitor_dirty, fsmonitor_ewah_callback, istate);

                        /* Now mark the untracked cache for fsmonitor usage */
                        if (istate->untracked)
                                istate->untracked->use_fsmonitor = 1;
                }

                ewah_free(istate->fsmonitor_dirty);
                istate->fsmonitor_dirty = NULL;
        }

        switch (fsmonitor_enabled) {
        case -1: /* keep: do nothing */
                break;
        case 0: /* false */
                remove_fsmonitor(istate);
                break;
        case 1: /* true */
                add_fsmonitor(istate);
                break;
        default: /* unknown value: do nothing */
                break;
        }
}