package main

import (
	"context"
	"fmt"
	"regexp"
	"strconv"
	"strings"

	"xorg/internal/desktop"
)

// The windows on the X screen, as the server knows them (xwininfo): what a window manager's own list
// (node-display-session.windows) leaves out — a window it does not manage, a dialog, a tooltip, a
// window that is mapped but drawn by nobody — and what a compositor goes by: the window's depth (32
// bits is a visual with an alpha channel, which a compositor blends with what is behind it), its type,
// whether it is mapped, and its own opacity.
//
// The tree comes from one `xwininfo -root -tree`. A window's details take one `xwininfo -all` and one
// `xprop` each, so they are read only for the windows asked about, and at most mostDetailed of them.

const mostDetailed = 40

// Window is one window of the tree, and its details when they were read.
type Window struct {
	ID       string `json:"window"`
	Name     string `json:"name,omitempty"`
	Instance string `json:"instance,omitempty"`
	Class    string `json:"class,omitempty"`
	Width    int    `json:"width"`
	Height   int    `json:"height"`
	X        int    `json:"x"`
	Y        int    `json:"y"`
	// Level is the window's depth in the tree: 1 is a child of the root (a frame or an unmanaged window).
	Level int `json:"level"`

	// The details (detail true, or a class asked for).
	Depth          int      `json:"depth,omitempty"`
	ARGB           *bool    `json:"argb,omitempty"`
	Visual         string   `json:"visual_class,omitempty"`
	Mapped         string   `json:"map_state,omitempty"`
	OverrideRedir  *bool    `json:"override_redirect,omitempty"`
	Types          []string `json:"types,omitempty"`
	States         []string `json:"states,omitempty"`
	Role           string   `json:"role,omitempty"`
	Opacity        *float64 `json:"opacity,omitempty"`
	DetailProblems string   `json:"detail_problem,omitempty"`
}

// treeLine is one line of `xwininfo -root -tree`: the id, the name (or "(has no name)"), the class
// pair when the window has one, the size and position relative to the parent, and the absolute one.
var treeLine = regexp.MustCompile(`^(\s*)(0x[0-9a-fA-F]+) (?:\(has no name\)|"(.*)"): \((?:"([^"]*)" "([^"]*)")?\)\s+(\d+)x(\d+)[+-]-?\d+[+-]-?\d+\s+\+?(-?\d+)\+?(-?\d+)\s*$`)

// ParseTree reads the windows of `xwininfo -root -tree`, in the server's stacking order per parent.
func ParseTree(text string) []Window {
	var out []Window
	for _, line := range strings.Split(text, "\n") {
		m := treeLine.FindStringSubmatch(line)
		if m == nil {
			continue
		}
		w := Window{ID: m[2], Name: m[3], Instance: m[4], Class: m[5]}
		w.Width, _ = strconv.Atoi(m[6])
		w.Height, _ = strconv.Atoi(m[7])
		w.X, _ = strconv.Atoi(m[8])
		w.Y, _ = strconv.Atoi(m[9])
		// xwininfo indents a child of the root by 5 spaces and each further level by 3.
		w.Level = 1 + (len(m[1])-5)/3
		out = append(out, w)
	}
	return out
}

// ParseDetails adds what `xwininfo -id <w> -all` says about one window.
func ParseDetails(w *Window, text string) {
	section := ""
	for _, raw := range strings.Split(text, "\n") {
		line := strings.TrimSpace(raw)
		indent := len(raw) - len(strings.TrimLeft(raw, " "))
		switch {
		case strings.HasPrefix(line, "Depth:"):
			w.Depth, _ = strconv.Atoi(strings.TrimSpace(strings.TrimPrefix(line, "Depth:")))
			argb := w.Depth == 32
			w.ARGB = &argb
			section = ""
		case strings.HasPrefix(line, "Visual Class:"):
			w.Visual = strings.TrimSpace(strings.TrimPrefix(line, "Visual Class:"))
		case strings.HasPrefix(line, "Map State:"):
			w.Mapped = strings.TrimSpace(strings.TrimPrefix(line, "Map State:"))
		case strings.HasPrefix(line, "Override Redirect State:"):
			v := strings.TrimSpace(strings.TrimPrefix(line, "Override Redirect State:")) == "yes"
			w.OverrideRedir = &v
		case line == "Window type:":
			section = "type"
		case line == "Window state:":
			section = "state"
		case line == "":
			section = ""
		case section != "" && indent >= 10:
			if section == "type" {
				w.Types = append(w.Types, line)
			} else {
				w.States = append(w.States, line)
			}
		default:
			if indent < 10 {
				section = ""
			}
		}
	}
}

// opacityLine and roleLine are the two properties read with xprop.
var (
	opacityLine = regexp.MustCompile(`^_NET_WM_WINDOW_OPACITY\(CARDINAL\) = (\d+)`)
	roleLine    = regexp.MustCompile(`^WM_WINDOW_ROLE\(STRING\) = "(.*)"`)
)

// ParseWindowProps adds the window's role and its own opacity (0 to 1) from xprop.
func ParseWindowProps(w *Window, text string) {
	for _, line := range strings.Split(text, "\n") {
		line = strings.TrimSpace(line)
		if m := opacityLine.FindStringSubmatch(line); m != nil {
			if n, err := strconv.ParseUint(m[1], 10, 32); err == nil {
				v := float64(n) / float64(0xffffffff)
				v = float64(int(v*1000+0.5)) / 1000
				w.Opacity = &v
			}
		}
		if m := roleLine.FindStringSubmatch(line); m != nil {
			w.Role = m[1]
		}
	}
}

func (x xorg) windows(ctx context.Context, a desktop.Args) (any, error) {
	classExpr := a.Opt("class", "")
	nameExpr := a.Opt("name", "")
	detail, _, err := a.Bool("detail")
	if err != nil {
		return nil, err
	}
	all, _, err := a.Bool("all")
	if err != nil {
		return nil, err
	}
	var classRe, nameRe *regexp.Regexp
	if classExpr != "" {
		if classRe, err = regexp.Compile(classExpr); err != nil {
			return nil, fmt.Errorf("class is a regular expression: %w", err)
		}
	}
	if nameExpr != "" {
		if nameRe, err = regexp.Compile(nameExpr); err != nil {
			return nil, fmt.Errorf("name is a regular expression: %w", err)
		}
	}
	res, s, err := x.d.InSession(ctx, "xwininfo", "-root", "-tree")
	if err != nil {
		return nil, err
	}
	if !res.OK() {
		if res.Code == 127 {
			return nil, fmt.Errorf("xwininfo is not installed here; the xorg module's package resource (xorg-xwininfo) installs it")
		}
		return nil, res.Err()
	}
	tree := ParseTree(res.Stdout)
	var shown []Window
	for _, w := range tree {
		switch {
		case classRe != nil && !(classRe.MatchString(w.Class) || classRe.MatchString(w.Instance)):
			continue
		case nameRe != nil && !nameRe.MatchString(w.Name):
			continue
		case classRe == nil && nameRe == nil && !all && w.Class == "":
			// Without a filter, the windows a program owns: those with a class.
			continue
		}
		shown = append(shown, w)
	}
	detailed := 0
	if detail || classRe != nil || nameRe != nil {
		env := s.Env(x.d.Base)
		for i := range shown {
			if detailed == mostDetailed {
				break
			}
			detailed++
			w := &shown[i]
			info := x.d.Run(ctx, env, nil, "xwininfo", "-id", w.ID, "-all")
			if !info.OK() {
				// A window can go between the tree and its details.
				w.DetailProblems = strings.TrimSpace(info.Stderr)
				continue
			}
			ParseDetails(w, info.Stdout)
			if props := x.d.Run(ctx, env, nil, "xprop", "-id", w.ID, "WM_WINDOW_ROLE", "_NET_WM_WINDOW_OPACITY"); props.OK() {
				ParseWindowProps(w, props.Stdout)
			}
		}
	}
	answer := map[string]any{"session": s.Display, "windows": shown, "count": len(shown), "in_tree": len(tree)}
	if detailed < len(shown) && (detail || classRe != nil || nameRe != nil) {
		answer["detailed"] = fmt.Sprintf("the first %d of %d; narrow class or name for the rest", detailed, len(shown))
	}
	return answer, nil
}

// windowGeometry is a window's absolute position and size, from `xwininfo -id`.
func (x xorg) windowGeometry(ctx context.Context, env []string, id string) (image4, error) {
	r := x.d.Run(ctx, env, nil, "xwininfo", "-id", id)
	if !r.OK() {
		if r.Code == 127 {
			return image4{}, fmt.Errorf("xwininfo is not installed here; the xorg module's package resource (xorg-xwininfo) installs it")
		}
		return image4{}, r.Err()
	}
	return ParseGeometry(r.Stdout)
}

// image4 is a rectangle on the screen, and the window's map state there.
type image4 struct {
	X, Y, W, H int
	Mapped     string
}

// ParseGeometry reads the absolute corner and the size from `xwininfo -id`.
func ParseGeometry(text string) (image4, error) {
	var g image4
	found := 0
	for _, raw := range strings.Split(text, "\n") {
		line := strings.TrimSpace(raw)
		for prefix, into := range map[string]*int{
			"Absolute upper-left X:": &g.X, "Absolute upper-left Y:": &g.Y, "Width:": &g.W, "Height:": &g.H,
		} {
			if strings.HasPrefix(line, "Map State:") {
				g.Mapped = strings.TrimSpace(strings.TrimPrefix(line, "Map State:"))
			}
			if strings.HasPrefix(line, prefix) {
				if n, err := strconv.Atoi(strings.TrimSpace(strings.TrimPrefix(line, prefix))); err == nil {
					*into = n
					found++
				}
			}
		}
	}
	if found < 4 || g.W <= 0 || g.H <= 0 {
		return image4{}, fmt.Errorf("xwininfo gave no geometry for the window")
	}
	return g, nil
}