var nThen = require("nthen");

var Store = require("../lib/storage/file");
var BlobStore = require("../lib/storage/blob");
var Pins = require("../lib/pins");
var config = require("../lib/load-config");

// the administrator should have set an 'inactiveTime' in their config
// if they didn't, just exit.
if (!config.inactiveTime || typeof(config.inactiveTime) !== "number") { return; }

// files which have not been changed since before this date can be considered inactive
var inactiveTime = +new Date() - (config.inactiveTime * 24 * 3600 * 1000);

// files which were archived before this date can be considered safe to remove
var retentionTime = +new Date() - (config.archiveRetentionTime * 24 * 3600 * 1000);

var getNewestTime = function (stats) {
    return stats[['atime', 'ctime', 'mtime'].reduce(function (a, b) {
        return stats[b] > stats[a]? b: a;
    })];
};

var store;
var pins;
var Log;
var blobs;

var startTime = +new Date();
var msSinceStart = function ()  {
    return (+new Date()) - startTime;
};

nThen(function (w) {
    // load the store which will be used for iterating over channels
    // and performing operations like archival and deletion
    Store.create(config, w(function (_) {
        store = _;
    })); // load the list of pinned files so you know which files
    // should not be archived or deleted
    Pins.list(w(function (err, _) {
        if (err) {
            w.abort();
            return void console.error(err);
        }
        pins = _;
    }), {
        pinPath: config.pinPath,
    });

    // load the logging module so that you have a record of which
    // files were archived or deleted at what time
    var Logger = require("../lib/log");
    Logger.create(config, w(function (_) {
        Log = _;
    }));

    config.getSession = function () {};
    BlobStore.create(config, w(function (err, _) {
        if (err) {
            w.abort();
            return console.error(err);
        }
        blobs = _;
    }));
}).nThen(function () {
    Log.info("EVICT_TIME_TO_LOAD_PINS", msSinceStart());
}).nThen(function (w) {
    // this block will iterate over archived channels and removes them
    // if they've been in cold storage for longer than your configured archive time

    // if the admin has not set an 'archiveRetentionTime', this block makes no sense
    // so just skip it
    if (typeof(config.archiveRetentionTime) !== "number") { return; }

    // count the number of files which have been removed in this run
    var removed = 0;

    var handler = function (err, item, cb) {
        if (err) {
            Log.error('EVICT_ARCHIVED_CHANNEL_ITERATION', err);
            return void cb();
        }
        // don't mess with files that are freshly stored in cold storage
        // based on ctime because that's changed when the file is moved...
        if (+new Date(item.ctime) > retentionTime) {
            return void cb();
        }

        // but if it's been stored for the configured time...
        // expire it
        store.removeArchivedChannel(item.channel, w(function (err) {
            if (err) {
                Log.error('EVICT_ARCHIVED_CHANNEL_REMOVAL_ERROR', {
                    error: err,
                    channel: item.channel,
                });
                return void cb();
            }
            Log.info('EVICT_ARCHIVED_CHANNEL_REMOVAL', item.channel);
            removed++;
            cb();
        }));
    };

    // if you hit an error, log it
    // otherwise, when there are no more channels to process
    // log some stats about how many were removed
    var done = function (err) {
        if (err) {
            return Log.error('EVICT_ARCHIVED_FINAL_ERROR', err);
        }
        Log.info('EVICT_ARCHIVED_CHANNELS_REMOVED', removed);
    };

    store.listArchivedChannels(handler, w(done));
}).nThen(function (w) {
    if (typeof(config.archiveRetentionTime) !== "number") { return; }
// Iterate over archive blob ownership proofs and remove them
// if they are older than the specified retention time
    var removed = 0;
    blobs.list.archived.proofs(function (err, item, next) {
        if (err) {
            Log.error("EVICT_BLOB_LIST_ARCHIVED_PROOF_ERROR", err);
            return void next();
        }
        if (pins[item.blobId]) { return void next(); }
        if (item && getNewestTime(item) > retentionTime) { return void next(); }
        blobs.remove.archived.proof(item.safeKey, item.blobId, (function (err) {
            if (err) {
                Log.error("EVICT_ARCHIVED_BLOB_PROOF_ERROR", item);
                return void next();
            }
            Log.info("EVICT_ARCHIVED_BLOB_PROOF", item);
            removed++;
            next();
        }));
    }, w(function () {
        Log.info('EVICT_ARCHIVED_BLOB_PROOFS_REMOVED', removed);
    }));
}).nThen(function (w) {
    if (typeof(config.archiveRetentionTime) !== "number") { return; }
// Iterate over archived blobs and remove them
// if they are older than the specified retention time
    var removed = 0;
    blobs.list.archived.blobs(function (err, item, next) {
        if (err) {
            Log.error("EVICT_BLOB_LIST_ARCHIVED_BLOBS_ERROR", err);
            return void next();
        }
        if (pins[item.blobId]) { return void next(); }
        if (item && getNewestTime(item) > retentionTime) { return void next(); }
        blobs.remove.archived.blob(item.blobId, function (err) {
            if (err) {
                Log.error("EVICT_ARCHIVED_BLOB_ERROR", item);
                return void next();
            }
            Log.info("EVICT_ARCHIVED_BLOB", item);
            removed++;
            next();
        });
    }, w(function () {
        Log.info('EVICT_ARCHIVED_BLOBS_REMOVED', removed);
    }));
}).nThen(function (w) {
// iterate over blobs and remove them
// if they have not been accessed within the specified retention time
    var removed = 0;
    blobs.list.blobs(function (err, item, next) {
        if (err) {
            Log.error("EVICT_BLOB_LIST_BLOBS_ERROR", err);
            return void next();
        }
        if (pins[item.blobId]) { return void next(); }
        if (item && getNewestTime(item) > retentionTime) { return void next(); }

        blobs.archive.blob(item.blobId, function (err) {
            if (err) {
                Log.error("EVICT_ARCHIVE_BLOB_ERROR", {
                    error: err,
                    item: item,
                });
                return void next();
            }
            Log.info("EVICT_ARCHIVE_BLOB", {
                item: item,
            });
            removed++;
            next();
        });
    }, w(function () {
        Log.info('EVICT_BLOBS_REMOVED', removed);
    }));
}).nThen(function (w) {
// iterate over blob proofs and remove them
// if they don't correspond to a pinned or active file
    var removed = 0;
    blobs.list.proofs(function (err, item, next) {
        if (err) {
            next();
            return void Log.error("EVICT_BLOB_LIST_PROOFS_ERROR", err);
        }
        if (pins[item.blobId]) { return void next(); }
        if (item && getNewestTime(item) > retentionTime) { return void next(); }
        nThen(function (w) {
            blobs.size(item.blobId, w(function (err, size) {
                if (err) {
                    w.abort();
                    next();
                    return void Log.error("EVICT_BLOB_LIST_PROOFS_ERROR", err);
                }
                if (size !== 0) {
                    w.abort();
                    next();
                }
            }));
        }).nThen(function () {
            blobs.remove.proof(item.safeKey, item.blobId, function (err) {
                next();
                if (err) {
                    return Log.error("EVICT_BLOB_PROOF_LONELY_ERROR", item);
                }
                removed++;
                return Log.info("EVICT_BLOB_PROOF_LONELY", item);
            });
        });
    }, w(function () {
        Log.info("EVICT_BLOB_PROOFS_REMOVED", removed);
    }));
}).nThen(function (w) {
    var channels = 0;
    var archived = 0;

    var handler = function (err, item, cb) {
        channels++;
        if (err) {
            Log.error('EVICT_CHANNEL_ITERATION', err);
            return void cb();
        }
        // check if the database has any ephemeral channels
        // if it does it's because of a bug, and they should be removed
        if (item.channel.length === 34) {
            return void store.removeChannel(item.channel, w(function (err) {
                if (err) {
                    Log.error('EVICT_EPHEMERAL_CHANNEL_REMOVAL_ERROR', {
                        error: err,
                        channel: item.channel,
                    });
                    return void cb();
                }
                Log.info('EVICT_EPHEMERAL_CHANNEL_REMOVAL', item.channel);
                cb();
            }));
        }

        // bail out if the channel was modified recently
        if (+new Date(item.mtime) > inactiveTime) { return void cb(); }

        // ignore the channel if it's pinned
        if (pins[item.channel]) { return void cb(); }

        return void store.archiveChannel(item.channel, w(function (err) {
            if (err) {
                Log.error('EVICT_CHANNEL_ARCHIVAL_ERROR', {
                    error: err,
                    channel: item.channel,
                });
                return void cb();
            }
            Log.info('EVICT_CHANNEL_ARCHIVAL', item.channel);
            archived++;
            cb();
        }));
    };

    var done = function () {
        return void Log.info('EVICT_CHANNELS_ARCHIVED', archived);
    };

    store.listChannels(handler, w(done));
}).nThen(function () {
    Log.info("EVICT_TIME_TO_RUN_SCRIPT", msSinceStart());
}).nThen(function () {
    // the store will keep this script running if you don't shut it down
    store.shutdown();
    Log.shutdown();
});