// Copyright (c) Liam Stanley <me@liamstanley.io>. All rights reserved. Use
// of this source code is governed by the MIT license that can be found in
// the LICENSE file.

package girc

import (
	"strings"
)

// Something not in the list? Depending on the type of capability, you can
// enable it using Config.SupportedCaps.
var possibleCap = map[string][]string{
	"account-notify":    nil,
	"account-tag":       nil,
	"away-notify":       nil,
	"batch":             nil,
	"cap-notify":        nil,
	"chghost":           nil,
	"extended-join":     nil,
	"invite-notify":     nil,
	"multi-prefix":      nil,
	"server-time":       nil,
	"userhost-in-names": nil,
	"message-tags":      nil,
	"msgid":             nil,

	// "echo-message" is supported, but it's not enabled by default. This is
	// to prevent unwanted confusion and utilize less traffic if it's not needed.
	// echo messages aren't sent to girc.PRIVMSG and girc.NOTICE handlers,
	// rather they are only sent to girc.ALL_EVENTS handlers (this is to prevent
	// each handler to have to check these types of things for each message).
	// You can compare events using Event.Equals() to see if they are the same.
}

// https://ircv3.net/specs/extensions/server-time-3.2.html
// <value> ::= YYYY-MM-DDThh:mm:ss.sssZ
const capServerTimeFormat = "2006-01-02T15:04:05.999Z"

func (c *Client) listCAP() {
	if !c.Config.disableTracking {
		c.write(&Event{Command: CAP, Params: []string{CAP_LS, "302"}})
	}
}

func possibleCapList(c *Client) map[string][]string {
	out := make(map[string][]string)

	if c.Config.SASL != nil {
		out["sasl"] = nil
	}

	for k := range c.Config.SupportedCaps {
		out[k] = c.Config.SupportedCaps[k]
	}

	for k := range possibleCap {
		out[k] = possibleCap[k]
	}

	return out
}

func parseCap(raw string) map[string][]string {
	out := make(map[string][]string)
	parts := strings.Split(raw, " ")

	var val int

	for i := 0; i < len(parts); i++ {
		val = strings.IndexByte(parts[i], prefixTagValue) // =

		// No value splitter, or has splitter but no trailing value.
		if val < 1 || len(parts[i]) < val+1 {
			// The capability doesn't contain a value.
			out[parts[i]] = nil
			continue
		}

		out[parts[i][:val]] = strings.Split(parts[i][val+1:], ",")
	}

	return out
}

// handleCAP attempts to find out what IRCv3 capabilities the server supports.
// This will lock further registration until we have acknowledged (or denied)
// the capabilities.
func handleCAP(c *Client, e Event) {
	if len(e.Params) >= 2 && (e.Params[1] == CAP_NEW || e.Params[1] == CAP_DEL) {
		c.listCAP()
		return
	}

	// We can assume there was a failure attempting to enable a capability.
	if len(e.Params) >= 2 && e.Params[1] == CAP_NAK {
		// Let the server know that we're done.
		c.write(&Event{Command: CAP, Params: []string{CAP_END}})
		return
	}

	possible := possibleCapList(c)

	if len(e.Params) >= 3 && e.Params[1] == CAP_LS {
		c.state.Lock()

		caps := parseCap(e.Last())

		for k := range caps {
			if _, ok := possible[k]; !ok {
				continue
			}

			if len(possible[k]) == 0 || len(caps[k]) == 0 {
				c.state.tmpCap = append(c.state.tmpCap, k)
				continue
			}

			var contains bool
			for i := 0; i < len(caps[k]); i++ {
				for j := 0; j < len(possible[k]); j++ {
					if caps[k][i] == possible[k][j] {
						// Assume we have a matching split value.
						contains = true
						goto checkcontains
					}
				}
			}

		checkcontains:
			if !contains {
				continue
			}

			c.state.tmpCap = append(c.state.tmpCap, k)
		}
		c.state.Unlock()

		// Indicates if this is a multi-line LS. (3 args means it's the
		// last LS).
		if len(e.Params) == 3 {
			// If we support no caps, just ack the CAP message and END.
			if len(c.state.tmpCap) == 0 {
				c.write(&Event{Command: CAP, Params: []string{CAP_END}})
				return
			}

			// Let them know which ones we'd like to enable.
			c.write(&Event{Command: CAP, Params: []string{CAP_REQ, strings.Join(c.state.tmpCap, " ")}})

			// Re-initialize the tmpCap, so if we get multiple 'CAP LS' requests
			// due to cap-notify, we can re-evaluate what we can support.
			c.state.Lock()
			c.state.tmpCap = []string{}
			c.state.Unlock()
		}
	}

	if len(e.Params) == 3 && e.Params[1] == CAP_ACK {
		c.state.Lock()
		c.state.enabledCap = strings.Split(e.Last(), " ")

		// Do we need to do sasl auth?
		wantsSASL := false
		for i := 0; i < len(c.state.enabledCap); i++ {
			if c.state.enabledCap[i] == "sasl" {
				wantsSASL = true
				break
			}
		}
		c.state.Unlock()

		if wantsSASL {
			c.write(&Event{Command: AUTHENTICATE, Params: []string{c.Config.SASL.Method()}})
			// Don't "CAP END", since we want to authenticate.
			return
		}

		// Let the server know that we're done.
		c.write(&Event{Command: CAP, Params: []string{CAP_END}})
		return
	}
}

// handleCHGHOST handles incoming IRCv3 hostname change events. CHGHOST is
// what occurs (when enabled) when a servers services change the hostname of
// a user. Traditionally, this was simply resolved with a quick QUIT and JOIN,
// however CHGHOST resolves this in a much cleaner fashion.
func handleCHGHOST(c *Client, e Event) {
	if len(e.Params) != 2 {
		return
	}

	c.state.Lock()
	user := c.state.lookupUser(e.Source.Name)
	if user != nil {
		user.Ident = e.Params[0]
		user.Host = e.Params[1]
	}
	c.state.Unlock()
	c.state.notify(c, UPDATE_STATE)
}

// handleAWAY handles incoming IRCv3 AWAY events, for which are sent both
// when users are no longer away, or when they are away.
func handleAWAY(c *Client, e Event) {
	c.state.Lock()
	user := c.state.lookupUser(e.Source.Name)
	if user != nil {
		user.Extras.Away = e.Last()
	}
	c.state.Unlock()
	c.state.notify(c, UPDATE_STATE)
}

// handleACCOUNT handles incoming IRCv3 ACCOUNT events. ACCOUNT is sent when
// a user logs into an account, logs out of their account, or logs into a
// different account. The account backend is handled server-side, so this
// could be NickServ, X (undernet?), etc.
func handleACCOUNT(c *Client, e Event) {
	if len(e.Params) != 1 {
		return
	}

	account := e.Params[0]
	if account == "*" {
		account = ""
	}

	c.state.Lock()
	user := c.state.lookupUser(e.Source.Name)
	if user != nil {
		user.Extras.Account = account
	}
	c.state.Unlock()
	c.state.notify(c, UPDATE_STATE)
}