// Package ui reads the phone screen and drives it.
//
// Reading uses `uiautomator dump`, which gives real element text and bounds.
// Acting uses `input`, which takes coordinates because that is all Android
// offers. Every tap is therefore derived from a text match in the dump — never
// from a hardcoded coordinate (FR-4).
package ui

import (
	"encoding/xml"
	"fmt"
	"regexp"
	"strconv"
	"strings"

	"gitea.lab.audasmedia.com.au/sam/artemis_control/internal/adb"
)

const dumpPath = "/sdcard/artemis_window_dump.xml"

// Node is one element in the uiautomator hierarchy.
type Node struct {
	Index       int    `xml:"index,attr"`
	Text        string `xml:"text,attr"`
	ResourceID  string `xml:"resource-id,attr"`
	Class       string `xml:"class,attr"`
	Package     string `xml:"package,attr"`
	ContentDesc string `xml:"content-desc,attr"`
	Clickable   bool   `xml:"clickable,attr"`
	Enabled     bool   `xml:"enabled,attr"`
	Scrollable  bool   `xml:"scrollable,attr"`
	Focused     bool   `xml:"focused,attr"`
	Selected    bool   `xml:"selected,attr"`
	Bounds      string `xml:"bounds,attr"`
	Children    []Node `xml:"node"`
}

// Hierarchy is a parsed uiautomator dump.
type Hierarchy struct {
	XMLName  xml.Name `xml:"hierarchy"`
	Rotation int      `xml:"rotation,attr"`
	Nodes    []Node   `xml:"node"`
}

// Dump fetches and parses the current screen.
func Dump(r *adb.Runner) (*Hierarchy, error) {
	if _, err := r.Shell("uiautomator dump " + dumpPath); err != nil {
		return nil, fmt.Errorf("uiautomator dump: %w", err)
	}
	raw, err := r.ExecOut("cat", dumpPath)
	if err != nil {
		return nil, fmt.Errorf("read ui dump: %w", err)
	}
	if len(raw) == 0 {
		return nil, fmt.Errorf("ui dump was empty")
	}
	return parseHierarchy(raw)
}

// parseHierarchy turns raw uiautomator XML into a Hierarchy.
func parseHierarchy(raw []byte) (*Hierarchy, error) {
	var h Hierarchy
	if err := xml.Unmarshal(raw, &h); err != nil {
		return nil, fmt.Errorf("parse ui dump: %w", err)
	}
	if len(h.Nodes) == 0 {
		return nil, fmt.Errorf("ui dump contained no nodes")
	}
	return &h, nil
}

// Walk visits a node and all of its children depth first.
func (n *Node) Walk(fn func(*Node)) {
	fn(n)
	for i := range n.Children {
		n.Children[i].Walk(fn)
	}
}

// Walk visits every node in the hierarchy.
func (h *Hierarchy) Walk(fn func(*Node)) {
	for i := range h.Nodes {
		h.Nodes[i].Walk(fn)
	}
}

// Label is the human-readable identity of a node, for logs and errors.
func (n *Node) Label() string {
	label := n.Text
	if label == "" {
		label = n.ContentDesc
	}
	return fmt.Sprintf("%s[%s] text=%q bounds=%s", n.Class, shortID(n.ResourceID), label, n.Bounds)
}

func shortID(id string) string {
	if id == "" {
		return "-"
	}
	if i := strings.LastIndex(id, "/"); i >= 0 {
		return id[i+1:]
	}
	return id
}

// IDSelector marks a selector that matches a resource id rather than text. A
// step that names "id:search_omnibox_text_box" finds the element with that
// resource id, whatever its visible label happens to be.
//
// This exists because some labels are not stable: the Google Maps search box
// carries a rotating hint as its content description ("Search here", "Try
// petrol stations, ATMs", ...), so a recipe that matched that text broke when
// the phone picked a different hint. The resource id does not rotate.
const IDSelector = "id:"

// FindText returns nodes whose text or content description matches query.
// When exact is false the match is case-insensitive and substring-based.
func (h *Hierarchy) FindText(query string, exact bool) []*Node {
	return h.find(query, exact, false)
}

// FindID returns nodes whose resource id matches query. When exact is false the
// match is case-insensitive and substring-based, so the short name
// "search_omnibox_text_box" matches the full
// "com.google.android.apps.maps:id/search_omnibox_text_box".
func (h *Hierarchy) FindID(query string, exact bool) []*Node {
	return h.find(query, exact, true)
}

// Find returns nodes matching a recipe selector. A selector that starts with
// "id:" is matched against the resource id; any other selector is matched
// against text and content description (FR-4).
func (h *Hierarchy) Find(query string, exact bool) []*Node {
	if id, ok := strings.CutPrefix(query, IDSelector); ok {
		return h.FindID(id, exact)
	}
	return h.FindText(query, exact)
}

func (h *Hierarchy) find(query string, exact, byID bool) []*Node {
	if query == "" {
		return nil
	}
	needle := strings.ToLower(query)
	var out []*Node
	h.Walk(func(n *Node) {
		var candidates []string
		if byID {
			if n.ResourceID != "" {
				candidates = []string{shortID(n.ResourceID), n.ResourceID}
			}
		} else {
			candidates = []string{n.Text, n.ContentDesc}
		}
		for _, candidate := range candidates {
			if candidate == "" {
				continue
			}
			if exact {
				if strings.EqualFold(candidate, query) {
					out = append(out, n)
					return
				}
				continue
			}
			if strings.Contains(strings.ToLower(candidate), needle) {
				out = append(out, n)
				return
			}
		}
	})
	return out
}

var boundsRe = regexp.MustCompile(`^\[(-?\d+),(-?\d+)\]\[(-?\d+),(-?\d+)\]$`)

// Rect is a screen rectangle in pixels.
type Rect struct {
	X1, Y1, X2, Y2 int
}

// Bounds parses the node's bounds attribute.
func (n *Node) BoundsRect() (Rect, error) {
	m := boundsRe.FindStringSubmatch(strings.TrimSpace(n.Bounds))
	if m == nil {
		return Rect{}, fmt.Errorf("node has no parsable bounds (%q)", n.Bounds)
	}
	vals := make([]int, 4)
	for i := 0; i < 4; i++ {
		v, err := strconv.Atoi(m[i+1])
		if err != nil {
			return Rect{}, fmt.Errorf("bad bounds %q: %w", n.Bounds, err)
		}
		vals[i] = v
	}
	r := Rect{X1: vals[0], Y1: vals[1], X2: vals[2], Y2: vals[3]}
	if r.X2 <= r.X1 || r.Y2 <= r.Y1 {
		return Rect{}, fmt.Errorf("node has empty bounds %q", n.Bounds)
	}
	return r, nil
}

// Center returns the centre point of the node, which is what a tap uses.
func (n *Node) Center() (int, int, error) {
	r, err := n.BoundsRect()
	if err != nil {
		return 0, 0, err
	}
	return (r.X1 + r.X2) / 2, (r.Y1 + r.Y2) / 2, nil
}