# cap.status:
# - sent (we have sent CAP LS 302, no terminal reply)
# - ack-wait (we've sent off the first REQ, wait for an ACK to update state and send END. will only transition when cap.req-inflight == {})
# - finished (all other CAP negotiation(CAP NEW) is handled asynchronously)
# cap.available: dict of CAPs advertised to us
# cap.req-inflight: set of inflight CAP REQs. aka a dict where the value is ignored
# cap.supporting: dict of cap -> callback pairs


# handling for CAP-related things
namespace eval ::cap {
  variable log [logger::init irc::cap]
  variable logp [logger::init irc::cap::parser]
  variable logh [logger::init irc::cap::dispatch]
  proc value_dict str {
    set ret {}
    foreach pair [split $str ","] {
      set value [join [lassign [split $pair "="] key] "="]
      dict set ret $key $value
    }
    return $ret
  }
  proc server_nack list {
    regsub -all { +} $list { } list
    foreach cap [split [string trim $list] " "] {
      lappend ret $cap
    }
    return $ret
  }
  proc server_ls list {
    regsub -all { +} $list { } list
    set caps {}
    foreach cap [split [string trim $list] " "] {
      set value [join [lassign [split $cap "="] capname] "="]
      # auto-parse registry capabilities
      switch -regexp -- $capname {
        {^(draft/account-registration|draft/metadata-2|draft/multiline|sts)$} {
          dict set caps $capname [value_dict $value]
        }
        {^(account-notify|account-tag|away-notify|batch|cap-notify|draft/channel-rename|draft/chathistory|chghost|echo-message|draft/event-playback|extended-join|extended-monitor|invite-notify|labeled-response|draft/message-redaction|message-tags|draft/metadata-notify-2|multi-prefix|draft/no-implicit-names|draft/pre-away|draft/read-marker|server-time|setname|standard-replies|userhost-in-names)$} {
          dict set caps $capname true
        }
        {^(draft/languages|sasl)$} {
          dict set caps $capname [split $value ","]
        }
        default {
          dict set caps $capname $value
        }
      }
    }
    return $caps
  }

  proc implied_caps caps {
    set ret {}
    set retd {}
    foreach cap $caps {
      switch -- $cap {
        draft/account-registration {
          lappend ret standard-replies
        }
        account-tag {
          lappend ret message-tags
        }
        batch {
          lappend ret message-tags
        }
        draft/chathistory {
          lappend ret batch server-time message-tags
        }
        
      }
    }
    foreach cap $ret {
      dict set retd $cap set
    }
    return $retd
  }

  proc parse_msg cmdargs {
    variable logp
    if {[llength $cmdargs] <= 2} {
      ${logp}::error "misbehaving server: sent [llength $cmdargs] args for CAP command: $cmdargs"
      return {success false}
    }
    set cmdargs [lassign $cmdargs target cmd]
    switch -- $cmd {
      LS {
        dict set ret type LS
        if {[llength $cmdargs] ni {1 2}} {
          ${logp}::error "misbehaving server: sent [expr {[llength $cmdargs]+2}] args for CAP LS command: $cmdargs"
          return {success false}
        }

        dict set ret success true
        if {[llength $cmdargs] == 2} {
          if {[lindex $cmdargs 0] != "*"} { ${logp}::warn "misbehaving server: sent [lindex $cmdargs 0] instead of * in CAP LS" }
          dict set ret multiline true
          dict set ret caps [server_ls [lindex $cmdargs 1]]
        } else {
          dict set ret multiline false
          dict set ret caps [server_ls [lindex $cmdargs 0]]
        }

        return $ret
      }
      NEW {
        dict set ret type NEW
        if {[llength $cmdargs] != 1} {
          ${logp}::error "misbehaving server: sent [expr {[llength $cmdargs]+2}] args for CAP LS command: $cmdargs"
          return {success false}
        }

        dict set ret success true
        dict set ret caps [server_ls [lindex $cmdargs 0]]

        return $ret
      }
      DEL {
        dict set ret type NEW
        if {[llength $cmdargs] != 1} {
          ${logp}::error "misbehaving server: sent [expr {[llength $cmdargs]+2}] args for CAP LS command: $cmdargs"
          return {success false}
        }

        dict set ret success true
        dict set ret caps [server_nack [lindex $cmdargs 0]]

        return $ret
      }
      ACK {
        dict set ret type ACK
        if {[llength $cmdargs] != 1} {
          ${logp}::error "misbehaving server: sent [expr {[llength $cmdargs]+2}] args for CAP ACK command: $cmdargs"
          return {success false}
        }
        dict set ret success true
        dict set ret caps [server_nack [lindex $cmdargs 0]]
      }
      NAK {
        dict set ret type NAK
        if {[llength $cmdargs] != 1} {
          ${logp}::error "misbehaving server: sent [expr {[llength $cmdargs]+2}] args for CAP NAK command: $cmdargs"
          return {success false}
        }
        dict set ret success true
        dict set ret caps [server_nack [lindex $cmdargs 0]]
      }
      LIST {
        dict set ret type LIST
        if {[llength $cmdargs] != 1} {
          ${logp}::error "misbehaving server: sent [expr {[llength $cmdargs]+2}] args for CAP LIST command: $cmdargs"
          return {success false}
        }
        dict set ret success true
        dict set ret caps [server_nack [lindex $cmdargs 0]]
      }
      default {
        ${logp}::error "misbehaving server: sent CAP $cmd message"
        return {success false}
      }
    }
  }

  proc test-cap {chan capname capval} {
    if [irc::meta exists $chan cap supporting $capname] {
      uplevel #0 [list apply [list {capname capval} [irc::meta get $chan cap supporting $capname]] $capname $capval]
    } else {
      return false
    }
  }

  proc apply-caps chan {
    variable logh
    if [llength [irc::meta get $chan cap req-inflight]] return
    foreach cap [dict keys [irc::meta get $chan cap to-change]] {
      if {[string range $cap 0 0] == "-"} {
        irc::meta unset $chan cap enabled $cap
      } else {
        irc::meta set $chan cap enabled $cap set
      }
    }
    irc::meta set $chan cap implied [implied_caps [dict keys [irc::meta get $chan cap enabled]]]
    irc::meta set $chan cap to-change {}
    if {[irc::meta get $chan cap status] == "ack-wait"} {
      irc::msg send $chan CAP END
      ${logh}::info "initial capability negotiation complete"
      irc::meta set $chan cap status "finished"
    }
  }

  proc req-cap {chan cap} {
    variable log
    ${log}::debug "attempting to negotiate $cap"
    irc::meta set $chan cap req-inflight $cap set
    irc::msg send $chan CAP REQ $cap
  }

  proc handler dispatch {
    variable logh
    ${logh}::debug "handling CAP message"

    set chan [dict get $dispatch chan]

    set parsed [parse_msg [dict get $dispatch params]]

    if ![dict get $parsed success] { ${logh}::error "got bad CAP message: [dict get $dispatch rawmsg]"; return }

    switch -- [dict get $parsed type] {
      LS {
        if [dict get $parsed multiline] {
          ${logh}::debug "accumulating multiline CAP LS"
          irc::meta set $chan cap ls-buffer [dict merge [irc::meta get $chan cap ls-buffer] [dict get $parsed caps]]
        } else {
          set available [dict merge [irc::meta get $chan cap ls-buffer] [dict get $parsed caps]]
          irc::meta set $chan cap available $available
          irc::meta set $chan cap ls-buffer {}

          set req_acc {}
          dict for {cap val} $available {
            # if we don't have a capability enabled, and we support it, request it
            if {![irc::meta exists $chan cap enabled $cap] && [test-cap $chan $cap $val]} {
              ${logh}::debug "attempting to negotiate $cap"
              irc::meta set $chan cap req-inflight $cap set

              if {[string length [concat $req_acc [list $cap]]] >= 500} {
                irc::msg send $chan CAP REQ $req_acc
                set $req_acc {}
              }
              lappend req_acc $cap
            }
          }
          if [string length $req_acc] {
            irc::msg send $chan CAP REQ $req_acc
          }

          if {[irc::meta get $chan cap status] == "sent"} {
            if [llength [irc::meta get $chan cap req-inflight]] {
              irc::meta set $chan cap status "ack-wait"
            } else {
              irc::meta set $chan cap status "finished"
              irc::msg send $chan CAP END
              ${logh}::info "initial capability negotiation ended early: no capabilities to negotiate"
            }
          }
        }
      }
      ACK {
        # TODO: hook for ACKed CAPs
        foreach cap [dict get $parsed caps] {
          ${logh}::info "CAP ACK: $cap"
          irc::meta unset $chan cap req-inflight $cap
          irc::meta set $chan cap to-change $cap set
        }
        apply-caps $chan
      }
      NAK {
        foreach cap [dict get $parsed caps] {
          ${logh}::warn "CAP NAK: $cap"
          irc::meta unset $chan cap req-inflight $cap
        }
        apply-caps $chan
      }
      NEW {
        dict for {cap val} [dict get $parsed caps] {
          # TODO: interface to check when CAPs change parameters and toggle them
          irc::meta set $chan cap available $cap $val
          if {![irc::meta exists $chan cap enabled $cap] && [test-cap $chan $cap $val]} {
            req-cap $chan $cap
          }
        }
      }
      DEL {
        foreach cap [dict get $parsed caps] {
          # TODO: cleanup hook for disabled CAPs
          irc::meta unset $chan cap available $cap
          irc::meta unset $chan cap enabled $cap
        }
      }
      LIST {
        irc::meta set $chan cap enabled {}
        foreach cap [dict get $parsed caps] {
          irc::meta set $chan cap enabled $cap set
        }
      }
    }
  }

  proc support {chan cap {script {return true}}} {
    variable log

    ${log}::info "supporting CAP $cap"
    # if we're not in early boot, and haven't already requested the capability, request it
    if {[irc::meta exists $chan cap status] && [irc::meta get $chan cap status] != "sent" && [irc::meta exists $chan cap available $cap] && ![irc::meta exists $chan cap supporting $cap]} {
      irc::meta set $chan cap supporting $cap $script
      if [test-cap $chan $cap [irc::meta get $chan cap available $cap]] {
        irc::meta set $chan cap req-inflight $cap set
        irc::msg send $chan CAP REQ $cap
      }
    } else {
      irc::meta set $chan cap supporting $cap $script
    }
  }

  proc negotiate {chan} {
    variable log

    ${log}::info "attempting capability negotiation for $chan ([irc::meta get $chan uri])"
    irc::meta set $chan cap ls-buffer {}
    irc::meta set $chan cap to-change {}
    irc::meta set $chan cap req-inflight {}
    irc::meta set $chan cap handler [irc::handler add $chan CAP { cap::handler $dispatch }]
    irc::meta set $chan cap status "sent"
    irc::msg send $chan CAP LS 302
  }
}