#include "TextEdit.hpp"

#include <algorithm>

#include "Utf8Util.hpp"

namespace jdi
{

	namespace
	{
		/** @brief 判断字符是否为 UTF-16 高位代理。 */
		bool IsHighSurrogate(wchar_t c)
		{
			return c >= 0xD800 && c <= 0xDBFF;
		}

		/** @brief 判断字符是否为 UTF-16 低位代理。 */
		bool IsLowSurrogate(wchar_t c)
		{
			return c >= 0xDC00 && c <= 0xDFFF;
		}

		/** @brief 判断字符是否符合数值输入（数字与科学计数法符号）。 */
		bool IsNumberChar(wchar_t c)
		{
			return (c >= L'0' && c <= L'9') || c == L'.' || c == L'-' || c == L'+' || c == L'e' || c == L'E';
		}

		/** @brief 判断字符是否为十六进制数字。 */
		bool IsHexDigit(wchar_t c)
		{
			return (c >= L'0' && c <= L'9') || (c >= L'a' && c <= L'f') || (c >= L'A' && c <= L'F');
		}

		/** @brief 判断字符是否为十进制数字。 */
		bool IsDigit(wchar_t c)
		{
			return c >= L'0' && c <= L'9';
		}
	}

	bool TextEdit::AcceptsCharacter(EditFilter filter, wchar_t character)
	{
		switch (filter)
		{
		case EditFilter::NUMBER:
			return IsNumberChar(character);
		case EditFilter::HEX:
			return IsHexDigit(character) || character == L'#';
		case EditFilter::BYTE:
			return IsDigit(character);
		case EditFilter::ANY:
		default:
			return character >= L' ' && character != 0x7F;
		}
	}

	void TextEdit::Begin(const std::wstring& text, bool selectAll, EditFilter filter, std::size_t maxLength)
	{
		m_active = true;
		m_text = text;
		m_filter = filter;
		m_maxLength = maxLength;
		m_caret = m_text.size();
		m_anchor = selectAll ? 0 : m_text.size();
		m_fresh = selectAll && !m_text.empty();
	}

	void TextEdit::End()
	{
		m_active = false;
		m_fresh = false;
		m_dragging = false;
		m_text.clear();
		m_caret = 0;
		m_anchor = 0;
		m_filter = EditFilter::ANY;
		m_maxLength = 0;
	}

	std::size_t TextEdit::ClampOffset(std::size_t offset) const
	{
		if (offset > m_text.size())
		{
			offset = m_text.size();
		}
		// 避免光标落在代理对中间（否则渲染与删除都会错位）。
		if (offset > 0 && offset < m_text.size() && IsLowSurrogate(m_text[offset]) &&
		    IsHighSurrogate(m_text[offset - 1]))
		{
			--offset;
		}
		return offset;
	}

	std::size_t TextEdit::StepLeft(std::size_t offset) const
	{
		if (offset == 0)
		{
			return 0;
		}
		--offset;
		if (offset > 0 && IsLowSurrogate(m_text[offset]) && IsHighSurrogate(m_text[offset - 1]))
		{
			--offset;
		}
		return offset;
	}

	std::size_t TextEdit::StepRight(std::size_t offset) const
	{
		if (offset >= m_text.size())
		{
			return m_text.size();
		}
		++offset;
		if (offset < m_text.size() && IsLowSurrogate(m_text[offset]) && IsHighSurrogate(m_text[offset - 1]))
		{
			++offset;
		}
		return offset;
	}

	bool TextEdit::ReplaceSelection(const std::wstring& replacement)
	{
		const bool hadSelection = HasSelection();
		const std::size_t begin = SelectionBegin();
		const std::size_t end = SelectionEnd();

		std::wstring merged = m_text.substr(0, begin) + replacement + m_text.substr(end);
		if (m_maxLength > 0 && merged.size() > m_maxLength)
		{
			merged.resize(m_maxLength);
		}

		const bool changed = (merged != m_text) || hadSelection;
		m_text = std::move(merged);
		m_caret = ClampOffset(begin + replacement.size());
		m_anchor = m_caret;
		m_fresh = false;
		return changed;
	}

	bool TextEdit::Insert(wchar_t character)
	{
		if (!m_active || character == 0)
		{
			return false;
		}
		if (!AcceptsCharacter(m_filter, character))
		{
			// ⚠️ 必须返回 false（= 内容未变化）：调用方会把返回值当作「是否已变化」用于重绘与回写，
			// 返回 true 会让被过滤器拒绝的按键显示成“已输入”。
			return false;
		}
		return ReplaceSelection(std::wstring(1, character));
	}

	bool TextEdit::Backspace()
	{
		if (!m_active)
		{
			return false;
		}
		if (HasSelection())
		{
			// 存在选区时退格清除整个选区。
			return ReplaceSelection(std::wstring());
		}
		if (m_caret == 0)
		{
			m_fresh = false;
			return false;
		}

		const std::size_t previous = StepLeft(m_caret);
		const std::size_t removed = m_caret - previous;
		m_text.erase(previous, removed);
		m_caret = previous;
		m_anchor = previous;
		m_fresh = false;
		return true;
	}

	bool TextEdit::DeleteForward()
	{
		if (!m_active)
		{
			return false;
		}
		if (HasSelection())
		{
			// 存在选区时删除键清除整个选区。
			return ReplaceSelection(std::wstring());
		}
		if (m_caret >= m_text.size())
		{
			m_fresh = false;
			return false;
		}

		const std::size_t next = StepRight(m_caret);
		m_text.erase(m_caret, next - m_caret);
		m_anchor = m_caret;
		m_fresh = false;
		return true;
	}

	bool TextEdit::MoveCaret(int delta, bool extendSelection)
	{
		if (!m_active || delta == 0)
		{
			return false;
		}

		// 未按 Shift 且存在选区时，左右键先「收拢」到选区的对应边缘（常规输入框行为）：
		// 左键跳到选区左端、右键跳到选区右端，而不是在光标处再移动一格。
		if (!extendSelection && HasSelection())
		{
			const std::size_t target = (delta < 0) ? SelectionBegin() : SelectionEnd();
			m_caret = target;
			m_anchor = target;
			m_fresh = false;
			return true;
		}

		std::size_t offset = m_caret;
		const int steps = (delta > 0) ? delta : -delta;
		for (int index = 0; index < steps; ++index)
		{
			offset = (delta > 0) ? StepRight(offset) : StepLeft(offset);
		}
		offset = ClampOffset(offset);

		if (offset == m_caret)
		{
			return false;
		}

		m_caret = offset;
		if (!extendSelection)
		{
			m_anchor = offset;
		}
		m_fresh = false;
		return true;
	}

	bool TextEdit::MoveHome(bool extendSelection)
	{
		if (!m_active)
		{
			return false;
		}

		// 未按 Shift 时 Home 必须收拢已有选区（例如整段选中后按 Home 应取消全选）。
		if (!extendSelection)
		{
			const bool changed = HasSelection() || (m_caret != 0);
			m_caret = 0;
			m_anchor = 0;
			m_fresh = false;
			return changed;
		}

		if (m_caret == 0)
		{
			return false;
		}
		m_caret = 0;
		m_fresh = false;
		return true;
	}

	bool TextEdit::MoveEnd(bool extendSelection)
	{
		if (!m_active)
		{
			return false;
		}

		// 同上：End 在未按 Shift 时收拢到行尾。
		if (!extendSelection)
		{
			const bool changed = HasSelection() || (m_caret != m_text.size());
			m_caret = m_text.size();
			m_anchor = m_caret;
			m_fresh = false;
			return changed;
		}

		if (m_caret == m_text.size())
		{
			return false;
		}
		m_caret = m_text.size();
		m_fresh = false;
		return true;
	}

	void TextEdit::SelectAll()
	{
		m_anchor = 0;
		m_caret = m_text.size();
		m_fresh = !m_text.empty();
	}

	bool TextEdit::DeselectToEnd()
	{
		if (!m_active)
		{
			return false;
		}

		const bool changed = HasSelection() || (m_caret != m_text.size());
		m_caret = m_text.size();
		m_anchor = m_caret;
		m_fresh = false;
		return changed;
	}

	void TextEdit::BeginDrag(std::size_t offset)
	{
		if (!m_active)
		{
			return;
		}
		const std::size_t target = ClampOffset(offset);
		m_caret = target;
		m_anchor = target;
		m_fresh = false;
		m_dragging = true;
	}

	bool TextEdit::UpdateDrag(std::size_t offset)
	{
		if (!m_active || !m_dragging)
		{
			return false;
		}
		const std::size_t target = ClampOffset(offset);
		if (target == m_caret)
		{
			return false;
		}
		m_caret = target;
		m_fresh = false;
		return true;
	}

	bool TextEdit::CopyToClipboard(HWND owner) const
	{
		if (m_text.empty())
		{
			return false;
		}
		const std::wstring payload =
		    HasSelection() ? m_text.substr(SelectionBegin(), SelectionEnd() - SelectionBegin()) : m_text;
		return CopyTextToClipboard(owner, payload);
	}

	bool TextEdit::CutToClipboard(HWND owner)
	{
		if (m_text.empty())
		{
			return false;
		}
		const bool copied = CopyToClipboard(owner);
		if (!copied)
		{
			return false;
		}
		if (HasSelection())
		{
			return ReplaceSelection(std::wstring());
		}
		// ⚠️ 没有选区时 Ctrl+X 只复制、**不清空**：与常规输入框一致。
		// 旧实现会 `m_text.clear()` ⇒ 用户想复制一个阈值/色号却把整个值删掉了。
		return false;
	}

	bool TextEdit::PasteFromClipboard(HWND owner)
	{
		if (!m_active)
		{
			return false;
		}

		std::wstring pasted;
		if (!PasteTextFromClipboard(owner, pasted))
		{
			return false;
		}

		// 按当前过滤策略清洗粘贴内容，避免数值框被灌入非法字符。
		std::wstring cleaned;
		cleaned.reserve(pasted.size());
		for (const wchar_t c : pasted)
		{
			if (AcceptsCharacter(m_filter, c))
			{
				cleaned.push_back(c);
			}
		}
		if (cleaned.empty())
		{
			return false;
		}
		return ReplaceSelection(cleaned);
	}

} // namespace jdi