// Copyright (c) 2026 Storm Dragon
// Authors: Storm Dragon, Angus Kola
// SPDX-License-Identifier: GPL-3.0-or-later
package internalui

import (
	"strconv"
	"strings"
	"unicode"
	"unicode/utf8"
)

func (s *Session) characterCount(n int) string {
	if n == 1 {
		return s.messages.T("1 character")
	}
	return s.messages.Format("{0} characters", strconv.Itoa(n))
}
func (s *Session) edit(control *Control, key Key) Result {
	if key.Name == "enter" {
		return Result{Action: control.Action}
	}
	characters := []rune(control.Text)
	start, end := min(s.cursor, s.anchor), max(s.cursor, s.anchor)
	if key.Ctrl && key.Name == "" {
		switch strings.ToLower(key.Text) {
		case "a":
			s.anchor, s.cursor = 0, len(characters)
			output := s.Presentation()
			output.Speech = s.messages.T("Selected all")
			return output
		case "v":
			return Result{Paste: true}
		case "c", "x":
			if control.Secret {
				output := s.Presentation()
				output.Speech = s.messages.T("Copy and cut are unavailable for password fields")
				return output
			}
			if start == end {
				return Result{}
			}
			text := string(characters[start:end])
			// Cutting is completed by the host only after clipboard write succeeds.
			return Result{Copy: &text}
		default:
			return Result{}
		}
	}
	if key.Name == "left" || key.Name == "right" || key.Name == "home" || key.Name == "end" {
		next := s.cursor
		switch key.Name {
		case "left":
			if !key.Shift && start != end {
				next = start
			} else {
				next = max(0, next-1)
				if key.Ctrl {
					for next > 0 && next < len(characters) && unicode.IsSpace(characters[next]) {
						next--
					}
					for next > 0 && !unicode.IsSpace(characters[next-1]) {
						next--
					}
				}
			}
		case "right":
			if !key.Shift && start != end {
				next = end
			} else {
				next = min(len(characters), next+1)
				if key.Ctrl {
					for next < len(characters) && !unicode.IsSpace(characters[next]) {
						next++
					}
					for next < len(characters) && unicode.IsSpace(characters[next]) {
						next++
					}
				}
			}
		case "home":
			next = 0
		case "end":
			next = len(characters)
		}
		s.cursor = next
		if !key.Shift {
			s.anchor = next
		}
		output := s.Presentation()
		if next == len(characters) {
			output.Speech = s.messages.T("End of text")
		} else if control.Secret {
			output.Speech = s.messages.T("Hidden character")
		} else {
			output.Speech = string(characters[next])
		}
		if key.Shift {
			output.Speech = s.messages.Format("{0}, selected", output.Speech)
		}
		return output
	}
	if key.Name == "backspace" || key.Name == "delete" {
		if start == end {
			if key.Name == "backspace" {
				start = max(0, start-1)
			} else {
				end = min(len(characters), end+1)
			}
		}
		if start == end {
			return Result{}
		}
		removed := string(characters[start:end])
		control.Text = string(append(characters[:start], characters[end:]...))
		s.cursor, s.anchor = start, start
		output := s.Presentation()
		if control.Secret {
			output.Speech = s.messages.Format("Deleted {0}", s.characterCount(end-start))
		} else {
			output.Speech = s.messages.Format("Deleted {0}", removed)
		}
		return output
	}
	if (key.Name == "" || key.Name == "space") && key.Text != "" && !key.Ctrl {
		return s.Insert(key.Text)
	}
	return Result{}
}

// Insert handles typing and paste atomically; invalid/oversized input leaves
// the field and selection untouched.
func (s *Session) Insert(text string) Result {
	if s.closed {
		return Result{}
	}
	if s.focus < 0 {
		return Result{}
	}
	control := &s.form.Tabs[s.tab].Controls[s.focus]
	if control.Kind != Entry {
		return Result{}
	}
	if !utf8.ValidString(text) {
		return Result{Speech: s.messages.T("Invalid text"), Braille: s.messages.T("Invalid text"), Cursor: -1}
	}
	characters := []rune(control.Text)
	start, end := min(s.cursor, s.anchor), max(s.cursor, s.anchor)
	inserted := []rune(text)
	for _, character := range inserted {
		if unicode.IsControl(character) {
			return Result{Speech: s.messages.T("Only single-line text is accepted"), Braille: s.messages.T("Only single-line text is accepted"), Cursor: -1}
		}
	}
	if len(characters)-(end-start)+len(inserted) > control.MaxLength {
		return Result{Speech: s.messages.T("Text limit reached"), Braille: s.messages.T("Text limit reached"), Cursor: -1}
	}
	control.Text = string(characters[:start]) + text + string(characters[end:])
	s.cursor, s.anchor = start+len(inserted), start+len(inserted)
	output := s.Presentation()
	if control.Secret {
		output.Speech = s.messages.Format("Inserted {0}", s.characterCount(len(inserted)))
	} else {
		output.Speech = text
	}
	return output
}