/* jslint node: true */
'use strict';

const msgDb					= require('./database.js').dbs.message;
const wordWrapText			= require('./word_wrap.js').wordWrapText;
const ftnUtil				= require('./ftn_util.js');
const createNamedUUID		= require('./uuid_util.js').createNamedUUID;
const Errors				= require('./enig_error.js').Errors;
const ANSI					= require('./ansi_term.js');
const {
	sanatizeString,
	getISOTimestampString }	= require('./database.js');

const {
	isAnsi, isFormattedLine,
	splitTextAtTerms,
	renderSubstr
}							= require('./string_util.js');

const ansiPrep				= require('./ansi_prep.js');

//	deps
const uuidParse				= require('uuid-parse');
const async					= require('async');
const _						= require('lodash');
const assert				= require('assert');
const moment				= require('moment');
const iconvEncode			= require('iconv-lite').encode;

const ENIGMA_MESSAGE_UUID_NAMESPACE 	= uuidParse.parse('154506df-1df8-46b9-98f8-ebb5815baaf8');

const WELL_KNOWN_AREA_TAGS = {
	Invalid		: '',
	Private		: 'private_mail',
	Bulletin	: 'local_bulletin',
};

const SYSTEM_META_NAMES = {
	LocalToUserID			: 'local_to_user_id',
	LocalFromUserID			: 'local_from_user_id',
	StateFlags0				: 'state_flags0',		//	See Message.StateFlags0
	ExplicitEncoding		: 'explicit_encoding',	//	Explicitly set encoding when exporting/etc.
	ExternalFlavor			: 'external_flavor',	//	"Flavor" of message - imported from or to be exported to. See Message.AddressFlavor
	RemoteToUser			: 'remote_to_user',		//	Opaque value depends on external system, e.g. FTN address
	RemoteFromUser			: 'remote_from_user',	//	Opaque value depends on external system, e.g. FTN address
};

//	Types for Message.SystemMetaNames.ExternalFlavor meta
const ADDRESS_FLAVOR = {
	Local		: 'local',	//	local / non-remote addressing
	FTN			: 'ftn',	//	FTN style
	Email		: 'email',
};

const STATE_FLAGS0 = {
	None		: 0x00000000,
	Imported	: 0x00000001,	//	imported from foreign system
	Exported	: 0x00000002,	//	exported to foreign system
};

//	:TODO: these should really live elsewhere...
const FTN_PROPERTY_NAMES = {
	//	packet header oriented
	FtnOrigNode			: 'ftn_orig_node',
	FtnDestNode			: 'ftn_dest_node',
	//	:TODO: rename these to ftn_*_net vs network - ensure things won't break, may need mapping
	FtnOrigNetwork		: 'ftn_orig_network',
	FtnDestNetwork		: 'ftn_dest_network',
	FtnAttrFlags		: 'ftn_attr_flags',
	FtnCost				: 'ftn_cost',
	FtnOrigZone			: 'ftn_orig_zone',
	FtnDestZone			: 'ftn_dest_zone',
	FtnOrigPoint		: 'ftn_orig_point',
	FtnDestPoint		: 'ftn_dest_point',

	//	message header oriented
	FtnMsgOrigNode		: 'ftn_msg_orig_node',
	FtnMsgDestNode		: 'ftn_msg_dest_node',
	FtnMsgOrigNet		: 'ftn_msg_orig_net',
	FtnMsgDestNet		: 'ftn_msg_dest_net',

	FtnAttribute		: 'ftn_attribute',

	FtnTearLine			: 'ftn_tear_line',		//	http://ftsc.org/docs/fts-0004.001
	FtnOrigin			: 'ftn_origin',			//	http://ftsc.org/docs/fts-0004.001
	FtnArea				: 'ftn_area',			//	http://ftsc.org/docs/fts-0004.001
	FtnSeenBy			: 'ftn_seen_by',		//	http://ftsc.org/docs/fts-0004.001
};

//	:TODO: this is a ugly hack due to bad variable names - clean it up & just _.camelCase(k)!
const MESSAGE_ROW_MAP = {
	reply_to_message_id	: 'replyToMsgId',
	modified_timestamp	: 'modTimestamp'
};

module.exports = class Message {
	constructor(
		{
			messageId = 0, areaTag = Message.WellKnownAreaTags.Invalid, uuid, replyToMsgId = 0,
			toUserName = '', fromUserName = '', subject = '', message = '', modTimestamp = moment(),
			meta, hashTags = [],
		} = { }
	)
	{
		this.messageId		= messageId;
		this.areaTag		= areaTag;
		this.uuid			= uuid;
		this.replyToMsgId	= replyToMsgId;
		this.toUserName		= toUserName;
		this.fromUserName	= fromUserName;
		this.subject		= subject;
		this.message		= message;

		if(_.isDate(modTimestamp) || _.isString(modTimestamp)) {
			modTimestamp = moment(modTimestamp);
		}

		this.modTimestamp	= modTimestamp;

		this.meta = {};
		_.defaultsDeep(this.meta, { System : {} }, meta);

		this.hashTags		= hashTags;
	}

	isValid() { return true; }	//	:TODO: obviously useless; look into this or remove it

	static isPrivateAreaTag(areaTag) {
		return areaTag.toLowerCase() === Message.WellKnownAreaTags.Private;
	}

	isPrivate() {
		return Message.isPrivateAreaTag(this.areaTag);
	}

	isFromRemoteUser() {
		return null !== _.get(this, 'meta.System.remote_from_user', null);
	}

	static get WellKnownAreaTags() {
		return WELL_KNOWN_AREA_TAGS;
	}

	static get SystemMetaNames() {
		return SYSTEM_META_NAMES;
	}

	static get AddressFlavor() {
		return ADDRESS_FLAVOR;
	}

	static get StateFlags0() {
		return STATE_FLAGS0;
	}

	static get FtnPropertyNames() {
		return FTN_PROPERTY_NAMES;
	}

	setLocalToUserId(userId) {
		this.meta.System = this.meta.System || {};
		this.meta.System[Message.SystemMetaNames.LocalToUserID] = userId;
	}

	setLocalFromUserId(userId) {
		this.meta.System = this.meta.System || {};
		this.meta.System[Message.SystemMetaNames.LocalFromUserID] = userId;
	}

	setRemoteToUser(remoteTo) {
		this.meta.System = this.meta.System || {};
		this.meta.System[Message.SystemMetaNames.RemoteToUser] = remoteTo;
	}

	setExternalFlavor(flavor) {
		this.meta.System = this.meta.System || {};
		this.meta.System[Message.SystemMetaNames.ExternalFlavor] = flavor;
	}

	static createMessageUUID(areaTag, modTimestamp, subject, body) {
		assert(_.isString(areaTag));
		assert(_.isDate(modTimestamp) || moment.isMoment(modTimestamp));
		assert(_.isString(subject));
		assert(_.isString(body));

		if(!moment.isMoment(modTimestamp)) {
			modTimestamp = moment(modTimestamp);
		}

		areaTag			= iconvEncode(areaTag.toUpperCase(), 'CP437');
		modTimestamp	= iconvEncode(modTimestamp.format('DD MMM YY  HH:mm:ss'), 'CP437');
		subject			= iconvEncode(subject.toUpperCase().trim(), 'CP437');
		body			= iconvEncode(body.replace(/\r\n|[\n\v\f\r\x85\u2028\u2029]/g, '').trim(), 'CP437');

		return uuidParse.unparse(createNamedUUID(ENIGMA_MESSAGE_UUID_NAMESPACE, Buffer.concat( [ areaTag, modTimestamp, subject, body ] )));
	}

	static getMessageFromRow(row) {
		const msg = {};
		_.each(row, (v, k) => {
			//	:TODO: see notes around MESSAGE_ROW_MAP -- clean this up so we can just _camelCase()!
			k = MESSAGE_ROW_MAP[k] || _.camelCase(k);
			msg[k] = v;
		});
		return msg;
	}

	/*
		Find message IDs or UUIDs by filter. Available filters/options:

		filter.uuids - use with resultType='id'
		filter.ids - use with resultType='uuid'
		filter.toUserName
		filter.fromUserName
		filter.replyToMesageId
		filter.newerThanTimestamp
		filter.newerThanMessageId
		filter.areaTag - note if you want by conf, send in all areas for a conf
		*filter.metaTuples - {category, name, value}

		filter.terms - FTS search

		filter.sort = modTimestamp | messageId
		filter.order = ascending | (descending)

		filter.limit
		filter.resultType = (id) | uuid | count
		filter.extraFields = []

		filter.privateTagUserId = <userId> - if set, only private messages belonging to <userId> are processed
		(any other areaTag or confTag filters will be ignored)

		*=NYI
	*/
	static findMessages(filter, cb) {
		filter = filter || {};

		filter.resultType	= filter.resultType || 'id';
		filter.extraFields	= filter.extraFields || [];

		if('messageList' === filter.resultType) {
			filter.extraFields = _.uniq(filter.extraFields.concat(
				[ 'area_tag', 'message_uuid', 'reply_to_message_id', 'to_user_name', 'from_user_name', 'subject', 'modified_timestamp' ]
			));
		}

		const field = 'uuid' === filter.resultType ? 'message_uuid' : 'message_id';

		if(moment.isMoment(filter.newerThanTimestamp)) {
			filter.newerThanTimestamp = getISOTimestampString(filter.newerThanTimestamp);
		}

		let sql;
		if('count' === filter.resultType) {
			sql =
				`SELECT COUNT() AS count
				FROM message m`;

		} else {
			sql =
				`SELECT DISTINCT m.${field}${filter.extraFields.length > 0 ? ', ' + filter.extraFields.map(f => `m.${f}`).join(', ') : ''}
				FROM message m`;
		}

		const sqlOrderDir = 'ascending' === filter.order ? 'ASC' : 'DESC';
		let sqlOrderBy;
		let sqlWhere = '';

		function appendWhereClause(clause) {
			if(sqlWhere) {
				sqlWhere += ' AND ';
			} else {
				sqlWhere += ' WHERE ';
			}
			sqlWhere += clause;
		}

		//	currently only avail sort
		if('modTimestamp' === filter.sort) {
			sqlOrderBy = `ORDER BY m.modified_timestamp ${sqlOrderDir}`;
		} else {
			sqlOrderBy = `ORDER BY m.message_id ${sqlOrderDir}`;
		}

		if(Array.isArray(filter.ids)) {
			appendWhereClause(`m.message_id IN (${filter.ids.join(', ')})`);
		}

		if(Array.isArray(filter.uuids)) {
			const uuidList = filter.uuids.map(u => `"${u}"`).join(', ');
			appendWhereClause(`m.message_id IN (${uuidList})`);
		}


		if(_.isNumber(filter.privateTagUserId)) {
			appendWhereClause(`m.area_tag = "${Message.WellKnownAreaTags.Private}"`);
			appendWhereClause(
				`m.message_id IN (
					SELECT message_id 
					FROM message_meta 
					WHERE meta_category = "System" AND meta_name = "${Message.SystemMetaNames.LocalToUserID}" AND meta_value = ${filter.privateTagUserId}
				)`);
		} else {
			if(filter.areaTag && filter.areaTag.length > 0) {
				if(Array.isArray(filter.areaTag)) {
					const areaList = filter.areaTag.map(t => `"${t}"`).join(', ');
					appendWhereClause(`m.area_tag IN(${areaList})`);
				} else if(_.isString(filter.areaTag)) {
					appendWhereClause(`m.area_tag = "${filter.areaTag}"`);
				}
			}
		}

		if(_.isNumber(filter.replyToMessageId)) {
			appendWhereClause(`m.reply_to_message_id=${filter.replyToMessageId}`);
		}		

		[ 'toUserName', 'fromUserName' ].forEach(field => {
			if(_.isString(filter[field]) && filter[field].length > 0) {
				appendWhereClause(`m.${_.snakeCase(field)} LIKE "${sanatizeString(filter[field])}"`);
			}
		});

		if(_.isString(filter.newerThanTimestamp) && filter.newerThanTimestamp.length > 0) {
			appendWhereClause(`DATETIME(m.modified_timestamp) > DATETIME("${filter.newerThanTimestamp}", "+1 seconds")`);
		}

		if(_.isNumber(filter.newerThanMessageId)) {
			appendWhereClause(`m.message_id > ${filter.newerThanMessageId}`);
		}

		if(filter.terms && filter.terms.length > 0) {
			//	note the ':' in MATCH expr., see https://www.sqlite.org/cvstrac/wiki?p=FullTextIndex
			appendWhereClause(
				`m.message_id IN (
					SELECT rowid
					FROM message_fts
					WHERE message_fts MATCH ":${sanatizeString(filter.terms)}"
				)`
			);
		}

		sql += `${sqlWhere} ${sqlOrderBy}`;

		if(_.isNumber(filter.limit)) {
			sql += ` LIMIT ${filter.limit}`;
		}

		sql += ';';

		if('count' === filter.resultType) {
			msgDb.get(sql, (err, row) => {
				return cb(err, row ? row.count : 0);
			});
		} else {
			const matches = [];
			const extra = filter.extraFields.length > 0;

			const rowConv = 'messageList' === filter.resultType ? Message.getMessageFromRow : row => row;

			msgDb.each(sql, (err, row) => {
				if(_.isObject(row)) {
					matches.push(extra ? rowConv(row) : row[field]);
				}
			}, err => {
				return cb(err, matches);
			});
		}
	}

	//	:TODO: use findMessages, by uuid, limit=1
	static getMessageIdByUuid(uuid, cb) {
		msgDb.get(
			`SELECT message_id
			FROM message
			WHERE message_uuid = ?
			LIMIT 1;`,
			[ uuid ],
			(err, row) => {
				if(err) {
					return cb(err);
				}

				const success = (row && row.message_id);
				return cb(
					success ? null : Errors.DoesNotExist(`No message for UUID ${uuid}`),
					success ? row.message_id : null
				);
			}
		);
	}

	//	:TODO: use findMessages
	static getMessageIdsByMetaValue(category, name, value, cb) {
		msgDb.all(
			`SELECT message_id
			FROM message_meta
			WHERE meta_category = ? AND meta_name = ? AND meta_value = ?;`,
			[ category, name, value ],
			(err, rows) => {
				if(err) {
					return cb(err);
				}
				return cb(null, rows.map(r => parseInt(r.message_id)));	//	return array of ID(s)
			}
		);
	}

	static getMetaValuesByMessageId(messageId, category, name, cb) {
		const sql =
			`SELECT meta_value
			FROM message_meta
			WHERE message_id = ? AND meta_category = ? AND meta_name = ?;`;

		msgDb.all(sql, [ messageId, category, name ], (err, rows) => {
			if(err) {
				return cb(err);
			}

			if(0 === rows.length) {
				return cb(Errors.DoesNotExist('No value for category/name'));
			}

			//	single values are returned without an array
			if(1 === rows.length) {
				return cb(null, rows[0].meta_value);
			}

			return cb(null, rows.map(r => r.meta_value));	//	map to array of values only
		});
	}

	static getMetaValuesByMessageUuid(uuid, category, name, cb) {
		async.waterfall(
			[
				function getMessageId(callback) {
					Message.getMessageIdByUuid(uuid, (err, messageId) => {
						return callback(err, messageId);
					});
				},
				function getMetaValues(messageId, callback) {
					Message.getMetaValuesByMessageId(messageId, category, name, (err, values) => {
						return callback(err, values);
					});
				}
			],
			(err, values) => {
				return cb(err, values);
			}
		);
	}

	loadMeta(cb) {
		/*
			Example of loaded this.meta:

			meta: {
				System: {
					local_to_user_id: 1234,
				},
				FtnProperty: {
					ftn_seen_by: [ "1/102 103", "2/42 52 65" ]
				}
			}
		*/
		const sql =
			`SELECT meta_category, meta_name, meta_value
			FROM message_meta
			WHERE message_id = ?;`;

		const self = this;	//	:TODO: not required - arrow functions below:
		msgDb.each(sql, [ this.messageId ], (err, row) => {
			if(!(row.meta_category in self.meta)) {
				self.meta[row.meta_category] = { };
				self.meta[row.meta_category][row.meta_name] = row.meta_value;
			} else {
				if(!(row.meta_name in self.meta[row.meta_category])) {
					self.meta[row.meta_category][row.meta_name] = row.meta_value;
				} else {
					if(_.isString(self.meta[row.meta_category][row.meta_name])) {
						self.meta[row.meta_category][row.meta_name] = [ self.meta[row.meta_category][row.meta_name] ];
					}

					self.meta[row.meta_category][row.meta_name].push(row.meta_value);
				}
			}
		}, err => {
			return cb(err);
		});
	}

	load(options, cb) {
		assert(_.isString(options.uuid));

		const self = this;

		async.series(
			[
				function loadMessage(callback) {
					msgDb.get(
						`SELECT message_id, area_tag, message_uuid, reply_to_message_id, to_user_name, from_user_name, subject,
						message, modified_timestamp, view_count
						FROM message
						WHERE message_uuid=?
						LIMIT 1;`,
						[ options.uuid ],
						(err, msgRow) => {
							if(err) {
								return callback(err);
							}

							if(!msgRow) {
								return callback(Errors.DoesNotExist('Message (no longer) available'));
							}

							self.messageId		= msgRow.message_id;
							self.areaTag		= msgRow.area_tag;
							self.messageUuid	= msgRow.message_uuid;
							self.replyToMsgId	= msgRow.reply_to_message_id;
							self.toUserName		= msgRow.to_user_name;
							self.fromUserName	= msgRow.from_user_name;
							self.subject		= msgRow.subject;
							self.message		= msgRow.message;
							self.modTimestamp	= moment(msgRow.modified_timestamp);

							return callback(err);
						}
					);
				},
				function loadMessageMeta(callback) {
					self.loadMeta(err => {
						return callback(err);
					});
				},
				function loadHashTags(callback) {
					//	:TODO:
					return callback(null);
				}
			],
			err => {
				return cb(err);
			}
		);
	}

	persistMetaValue(category, name, value, transOrDb, cb) {
		if(!_.isFunction(cb) && _.isFunction(transOrDb)) {
			cb = transOrDb;
			transOrDb = msgDb;
		}

		const metaStmt = transOrDb.prepare(
			`INSERT INTO message_meta (message_id, meta_category, meta_name, meta_value) 
			VALUES (?, ?, ?, ?);`);

		if(!_.isArray(value)) {
			value = [ value ];
		}

		const self = this;

		async.each(value, (v, next) => {
			metaStmt.run(self.messageId, category, name, v, err => {
				return next(err);
			});
		}, err => {
			return cb(err);
		});
	}

	persist(cb) {
		if(!this.isValid()) {
			return cb(Errors.Invalid('Cannot persist invalid message!'));
		}

		const self = this;

		async.waterfall(
			[
				function beginTransaction(callback) {
					return msgDb.beginTransaction(callback);
				},
				function storeMessage(trans, callback) {
					//	generate a UUID for this message if required (general case)
					const msgTimestamp = moment();
					if(!self.uuid) {
						self.uuid = Message.createMessageUUID(
							self.areaTag,
							msgTimestamp,
							self.subject,
							self.message
						);
					}

					trans.run(
						`INSERT INTO message (area_tag, message_uuid, reply_to_message_id, to_user_name, from_user_name, subject, message, modified_timestamp)
						VALUES (?, ?, ?, ?, ?, ?, ?, ?);`,
						[ self.areaTag, self.uuid, self.replyToMsgId, self.toUserName, self.fromUserName, self.subject, self.message, getISOTimestampString(msgTimestamp) ],
						function inserted(err) {	//	use non-arrow function for 'this' scope
							if(!err) {
								self.messageId = this.lastID;
							}

							return callback(err, trans);
						}
					);
				},
				function storeMeta(trans, callback) {
					if(!self.meta) {
						return callback(null, trans);
					}
					/*
						Example of self.meta:

						meta: {
							System: {
								local_to_user_id: 1234,
							},
							FtnProperty: {
								ftn_seen_by: [ "1/102 103", "2/42 52 65" ]
							}
						}
					*/
					async.each(Object.keys(self.meta), (category, nextCat) => {
						async.each(Object.keys(self.meta[category]), (name, nextName) => {
							self.persistMetaValue(category, name, self.meta[category][name], trans, err => {
								return nextName(err);
							});
						}, err => {
							return nextCat(err);
						});

					}, err => {
						return callback(err, trans);
					});
				},
				function storeHashTags(trans, callback) {
					//	:TODO: hash tag support
					return callback(null, trans);
				}
			],
			(err, trans) => {
				if(trans) {
					trans[err ? 'rollback' : 'commit'](transErr => {
						return cb(err ? err : transErr, self.messageId);
					});
				} else {
					return cb(err);
				}
			}
		);
	}

	//	:TODO: FTN stuff doesn't have any business here
	getFTNQuotePrefix(source) {
		source = source || 'fromUserName';

		return ftnUtil.getQuotePrefix(this[source]);
	}

	getTearLinePosition(input) {
		const m = input.match(/^--- .+$(?![\s\S]*^--- .+$)/m);
		return m ? m.index : -1;
	}

	getQuoteLines(options, cb) {
		if(!options.termWidth || !options.termHeight || !options.cols) {
			return cb(Errors.MissingParam());
		}

		options.startCol			= options.startCol || 1;
		options.includePrefix 		= _.get(options, 'includePrefix', true);
		options.ansiResetSgr		= options.ansiResetSgr || ANSI.getSGRFromGraphicRendition( { fg : 39, bg : 49 }, true);
		options.ansiFocusPrefixSgr	= options.ansiFocusPrefixSgr || ANSI.getSGRFromGraphicRendition( { intensity : 'bold', fg : 39, bg : 49 } );
		options.isAnsi				= options.isAnsi || isAnsi(this.message);	//	:TODO: If this.isAnsi, use that setting

		/*
			Some long text that needs to be wrapped and quoted should look right after
			doing so, don't ya think? yeah I think so

			Nu> Some long text that needs to be wrapped and quoted should look right
			Nu> after doing so, don't ya think? yeah I think so

			Ot> Nu> Some long text that needs to be wrapped and quoted should look
			Ot> Nu> right after doing so, don't ya think? yeah I think so

		*/
		const quotePrefix = options.includePrefix ? this.getFTNQuotePrefix(options.prefixSource || 'fromUserName') : '';

		function getWrapped(text, extraPrefix) {
			extraPrefix = extraPrefix ? ` ${extraPrefix}` : '';

			const wrapOpts = {
				width		: options.cols - (quotePrefix.length + extraPrefix.length),
				tabHandling	: 'expand',
				tabWidth	: 4,
			};

			return wordWrapText(text, wrapOpts).wrapped.map( (w, i) => {
				return i === 0 ? `${quotePrefix}${w}` : `${quotePrefix}${extraPrefix}${w}`;
			});
		}

		function getFormattedLine(line) {
			//	for pre-formatted text, we just append a line truncated to fit
			let newLen;
			const total = line.length + quotePrefix.length;

			if(total > options.cols) {
				newLen = options.cols - total;
			} else {
				newLen = total;
			}

			return `${quotePrefix}${line.slice(0, newLen)}`;
		}

		if(options.isAnsi) {
			ansiPrep(
				this.message.replace(/\r?\n/g, '\r\n'),	//	normalized LF -> CRLF
				{
					termWidth		: options.termWidth,
					termHeight		: options.termHeight,
					cols			: options.cols,
					rows			: 'auto',
					startCol		: options.startCol,
					forceLineTerm	: true,
				},
				(err, prepped) => {
					prepped = prepped || this.message;

					let lastSgr = '';
					const split = splitTextAtTerms(prepped);

					const quoteLines		= [];
					const focusQuoteLines	= [];

					//
					//	Do not include quote prefixes (e.g. XX> ) on ANSI replies (and therefor quote builder)
					//	as while this works in ENiGMA, other boards such as Mystic, WWIV, etc. will try to
					//	strip colors, colorize the lines, etc. If we exclude the prefixes, this seems to do
					//	the trick and allow them to leave them alone!
					//
					split.forEach(l => {
						quoteLines.push(`${lastSgr}${l}`);

						focusQuoteLines.push(`${options.ansiFocusPrefixSgr}>${lastSgr}${renderSubstr(l, 1, l.length - 1)}`);
						lastSgr = (l.match(/(?:\x1b\x5b)[?=;0-9]*m(?!.*(?:\x1b\x5b)[?=;0-9]*m)/) || [])[0] || '';	//	eslint-disable-line no-control-regex
					});

					quoteLines[quoteLines.length - 1] += options.ansiResetSgr;

					return cb(null, quoteLines, focusQuoteLines, true);
				}
			);
		} else {
			const QUOTE_RE	= /^ ((?:[A-Za-z0-9]{2}> )+(?:[A-Za-z0-9]{2}>)*) */;
			const quoted	= [];
			const input		= _.trimEnd(this.message).replace(/\b/g, '');

			//	find *last* tearline
			let tearLinePos = this.getTearLinePosition(input);
			tearLinePos = -1 === tearLinePos ? input.length : tearLinePos;	//	we just want the index or the entire string

			input.slice(0, tearLinePos).split(/\r\n\r\n|\n\n/).forEach(paragraph => {
				//
				//	For each paragraph, a state machine:
				//	- New line - line
				//	- New (pre)quoted line - quote_line
				//	- Continuation of new/quoted line
				//
				//	Also:
				//	- Detect pre-formatted lines & try to keep them as-is
				//
				let state;
				let buf = '';
				let quoteMatch;

				if(quoted.length > 0) {
					//
					//	Preserve paragraph seperation.
					//
					//	FSC-0032 states something about leaving blank lines fully blank
					//	(without a prefix) but it seems nicer (and more consistent with other systems)
					//	to put 'em in.
					//
					quoted.push(quotePrefix);
				}

				paragraph.split(/\r?\n/).forEach(line => {
					if(0 === line.trim().length) {
						//	see blank line notes above
						return quoted.push(quotePrefix);
					}

					quoteMatch = line.match(QUOTE_RE);

					switch(state) {
						case 'line' :
							if(quoteMatch) {
								if(isFormattedLine(line)) {
									quoted.push(getFormattedLine(line.replace(/\s/, '')));
								} else {
									quoted.push(...getWrapped(buf, quoteMatch[1]));
									state = 'quote_line';
									buf = line;
								}
							} else {
								buf += ` ${line}`;
							}
							break;

						case 'quote_line' :
							if(quoteMatch) {
								const rem = line.slice(quoteMatch[0].length);
								if(!buf.startsWith(quoteMatch[0])) {
									quoted.push(...getWrapped(buf, quoteMatch[1]));
									buf = rem;
								} else {
									buf += ` ${rem}`;
								}
							} else {
								quoted.push(...getWrapped(buf));
								buf = line;
								state = 'line';
							}
							break;

						default :
							if(isFormattedLine(line)) {
								quoted.push(getFormattedLine(line));
							} else {
								state	= quoteMatch ? 'quote_line' : 'line';
								buf		= 'line' === state ? line : line.replace(/\s/, '');	//	trim *first* leading space, if any
							}
							break;
					}
				});

				quoted.push(...getWrapped(buf, quoteMatch ? quoteMatch[1] : null));
			});

			input.slice(tearLinePos).split(/\r?\n/).forEach(l => {
				quoted.push(...getWrapped(l));
			});

			return cb(null, quoted, null, false);
		}
	}
};