package main

import (
    "fmt"
    "log"
    "os"
    "os/exec"

    "github.com/jezek/xgb"
    "github.com/jezek/xgb/xinerama"
    "github.com/jezek/xgb/xproto"
)

// TODO: Make a separate keysym file and fully populate it.
const (
    XK_q      = 0x0071
    XK_Return = 0xff0d
)

type display struct {
    screen    xinerama.ScreenInfo
    windows   []xproto.Window
}

func main() {
    // Set ourselves up as the new window manager ------------------------------

    xconn := connectToXServer()
    xroot := getXRoot(xconn)
    keymap := getKeyboardMap(xconn)
    registerForKeyEvents(xconn, xroot, keymap)

    becomeWM(xconn, xroot)

    // Build a list of output devices ------------------------------------------

    var attachedDisplays []display
    for _, screen := range getAttachedScreens(xconn) {
        attachedDisplays = append(attachedDisplays, display{screen: screen})
    }
    // TODO: Verify some displays actually exist and we don't have an empty array. Otherwise, die here.
    // TODO: Should this all go in its own function and simply return attachedDisplays[] here instead? What will my fundamental data structure be?

    // Build a list of windows needing management ------------------------------

    // TODO: The following should all be an initialization function. It should not be here.
    tree, err := xproto.QueryTree(xconn, xroot.Root).Reply()
    if err != nil {
        // TODO: Better error
        log.Fatal(err)
    }
    if tree != nil {
        for _, c := range tree.Children {
            if isMappedWindow(xconn, c) {
                // For now, dump any pre-existing windows into the first
                // display. Later we can add functionality for tracking window
                // attributes across window manager restarts.
                attachedDisplays[0].windows = append(attachedDisplays[0].windows, c)
            }

        }
        // TODO: Try tiling/displaying/whatever with any existing windows before entering the event loop.
    }

    // Main program loop reacts to X events ------------------------------------

eventloop:
    for {
        fmt.Printf("ILLI: attachedDisplays: ")
        fmt.Println(attachedDisplays)
        xevent, err := xconn.WaitForEvent()
        if err != nil {
            log.Println(err)
            continue
        }
        switch e := xevent.(type) {
            case xproto.KeyPressEvent:
                fmt.Printf("ILLI: Received xproto.KeyPressEvent\n")
                if err := handleKeyPressEvent(keymap, e); err != nil {
                    break eventloop
                }
            case xproto.KeyReleaseEvent:
                fmt.Printf("ILLI: Received xproto.KeyReleaseEvent\n")
            case xproto.DestroyNotifyEvent:
                fmt.Printf("ILLI: Received xproto.DestroyNotifyEvent\n")
            case xproto.ConfigureRequestEvent:
                fmt.Printf("ILLI: Received xproto.ConfigureRequestEvent\n")
                rewrittenEvent := xproto.ConfigureNotifyEvent{
                    Event:            e.Window,
                    Window:           e.Window,
                    AboveSibling:     0,
                    X:                e.X,
                    Y:                e.Y,
                    Width:            e.Width,
                    Height:           e.Height,
                    BorderWidth:      0,
                    OverrideRedirect: false,
                }
                xproto.SendEventChecked(xconn, false, e.Window, xproto.EventMaskStructureNotify, string(rewrittenEvent.Bytes()))
            case xproto.MapRequestEvent:
                fmt.Printf("ILLI: Received xproto.MapRequestEvent\n")
                if windowAttributes, err := xproto.GetWindowAttributes(xconn, e.Window).Reply(); err != nil || !windowAttributes.OverrideRedirect {
                    xproto.MapWindowChecked(xconn, e.Window)
                    attachedDisplays[0].windows = append(attachedDisplays[0].windows, e.Window)

                    if err := xproto.ConfigureWindowChecked (
                        xconn,
                        attachedDisplays[0].windows[0],
                        xproto.ConfigWindowX |
                            xproto.ConfigWindowY |
                            xproto.ConfigWindowWidth |
                            xproto.ConfigWindowHeight,
                        []uint32{
                            uint32(100), // TODO: Temporarily hardcoding for testing.
                            uint32(100), // TODO: Temporarily hardcoding for testing.
                            uint32(1720), // TODO: Temporarily hardcoding for testing.
                            uint32(1000), // TODO: Temporarily hardcoding for testing.
                        }).Check(); err != nil {
                        fmt.Println("ILLI: Failed to handle MapRequestEvent")
                    }

                }
            case xproto.EnterNotifyEvent:
                fmt.Printf("ILLI: Received xproto.EnterNotifyEvent\n")
            default:
                fmt.Printf("ILLI: Unknown X event received: %s\n", xevent)
        }
    }
}

// The client list appears to have some entries for windows that shouldn't
// actually be viewable. For now, it appears that only windows with a
// `MapState` value of 2 should be viewable. TODO: Verify this.
//   - https://github.com/BurntSushi/xgb/blob/master/xproto/xproto.go#L3772
//   - https://github.com/BurntSushi/xgb/blob/master/xproto/xproto.go#L10287
func isMappedWindow(conn *xgb.Conn, windowID xproto.Window) bool {
    reply, err := xproto.GetWindowAttributes(conn, windowID).Reply()
    if err != nil {
        log.Fatal(err)
    }
    if reply != nil && reply.MapState == 2 {
        return true
    }
    return false
}

// TODO: Determine how I want to split the main event loop from the various
// event handlers (like this keypress handler). It shouldn't grow too
// fragmented, nor should it grow into a monolithic beast, but the balance
// needs to be selected after the handlers are built out more completely.
func handleKeyPressEvent(keymap [256][]xproto.Keysym, key xproto.KeyPressEvent) error {
    switch keymap[key.Detail][0] {
        case XK_q:
            switch key.State {
                case xproto.ModMask1 | xproto.ModMaskShift:
                    // TODO: Where and how do I want to handle exit/restart?
                    // -------------------------
                    // We must manually close the X connection since we used
                    // `defer` when setting it up and os.Exit() short-circuits
                    // that deferral.
                    //xc.Close()
                    os.Exit(0)
            }
        case XK_Return:
            switch key.State {
                case xproto.ModMask1 | xproto.ModMaskShift:
                    cmd := exec.Command("xterm")
                    err := cmd.Start()
                    if err != nil {
                        log.Fatal(err)
                    }
            }
        default:
            return nil
    }
    return nil // TODO: What do I actually want to return here?
}