#pragma once

#include <string>
#include <vector>
#include <functional>
#include <optional>
#include <filesystem>
#include <memory>

namespace lumacs {

/// Represents a cursor position in a buffer
struct Position {
    size_t line;
    size_t column;

    auto operator<=>(const Position&) const = default;
};

/// Represents a range in the buffer
struct Range {
    Position start;
    Position end;

    auto operator<=>(const Range&) const = default;
};

/// Buffer events for hooks/callbacks
enum class BufferEvent {
    // Lifecycle events
    Created,        // Buffer was created
    Loaded,         // File was loaded into buffer
    Closed,         // Buffer is being closed

    // Modification events
    BeforeChange,   // About to modify buffer (can be used to save state for undo)
    AfterChange,    // Buffer content was modified
    LineChanged,    // Specific line was modified

    // File operations
    BeforeSave,     // About to save
    AfterSave,      // File was saved

    // Language/mode
    LanguageChanged // Buffer language/mode changed
};

/// Event data passed to callbacks
struct BufferEventData {
    BufferEvent event;
    size_t line = 0;           // Line number for LineChanged events
    std::string language = ""; // For LanguageChanged events
};

/// Text styling attributes for syntax highlighting
struct TextAttribute {
    enum class Style {
        Normal = 0,
        Bold = 1,
        Italic = 2,
        Underline = 4,
        // Can combine with bitwise OR
    };

    // Common semantic colors for syntax highlighting
    enum class ColorType {
        Default,
        Keyword,      // if, for, while, etc.
        String,       // String literals
        Comment,      // Comments
        Function,     // Function names
        Type,         // Type names, classes
        Number,       // Numeric literals
        Operator,     // +, -, *, etc.
        Variable,     // Variable names
        Constant,     // Constants, enums
        Error,        // Error highlighting
    };

    ColorType color = ColorType::Default;
    int style_flags = 0; // Combination of Style flags

    TextAttribute() = default;
    TextAttribute(ColorType c, int s = 0) : color(c), style_flags(s) {}
};

/// A range with associated styling
struct StyledRange {
    Range range;
    TextAttribute attr;

    StyledRange() = default;
    StyledRange(Range r, TextAttribute a) : range(r), attr(a) {}
};

/// Undo/Redo state snapshot
struct UndoState {
    std::vector<std::string> lines;
    Position cursor;

    UndoState() = default;
    UndoState(const std::vector<std::string>& l, Position c) : lines(l), cursor(c) {}
};

/// A text buffer that manages the content of a file or scratch buffer
class Buffer {
public:
    /// Create an empty buffer
    Buffer();

    /// Create a buffer with a name (for scratch buffers)
    explicit Buffer(std::string name);

    /// Create a buffer from a file
    static std::optional<Buffer> from_file(const std::filesystem::path& path);

    // Disable copy, allow move
    Buffer(const Buffer&) = delete;
    Buffer& operator=(const Buffer&) = delete;
    Buffer(Buffer&&) noexcept = default;
    Buffer& operator=(Buffer&&) noexcept = default;

    ~Buffer() = default;

    // === Content Access ===

    /// Get the number of lines in the buffer
    [[nodiscard]] size_t line_count() const noexcept;

    /// Get a line by index (0-based)
    [[nodiscard]] const std::string& line(size_t index) const;

    /// Get all lines
    [[nodiscard]] const std::vector<std::string>& lines() const noexcept;

    /// Get the entire buffer content as a single string
    [[nodiscard]] std::string content() const;

    // === Modification ===

    /// Insert text at a position
    void insert(Position pos, std::string_view text);

    /// Insert a character at a position
    void insert_char(Position pos, char c);

    /// Insert a newline at a position
    void insert_newline(Position pos);

    /// Delete a range of text
    void erase(Range range);

    /// Delete a character at a position (backspace)
    void erase_char(Position pos);

    /// Replace text in a range
    void replace(Range range, std::string_view text);

    /// Find text starting from a position
    [[nodiscard]] std::optional<Range> find(const std::string& query, Position start_pos) const;

    /// Clear the entire buffer
    void clear();

    // === File Operations ===

    /// Save the buffer to its associated file
    bool save();

    /// Save the buffer to a specific file
    bool save_as(const std::filesystem::path& path);

    /// Check if the buffer has been modified since last save
    [[nodiscard]] bool is_modified() const noexcept;

    /// Get the file path associated with this buffer (if any)
    [[nodiscard]] std::optional<std::filesystem::path> file_path() const noexcept;

    // === Buffer Properties ===

    /// Get the buffer name
    [[nodiscard]] const std::string& name() const noexcept;

    /// Set the buffer name
    void set_name(std::string name);

    /// Check if position is valid
    [[nodiscard]] bool is_valid_position(Position pos) const noexcept;

    /// Clamp a position to valid bounds
    [[nodiscard]] Position clamp_position(Position pos) const noexcept;

    // === Syntax Highlighting / Styling ===

    /// Set styling for a range of text
    void set_style(Range range, TextAttribute attr);

    /// Get all styled ranges for a specific line
    [[nodiscard]] const std::vector<StyledRange>& get_line_styles(size_t line) const;

    /// Clear all styling information
    void clear_styles();

    /// Clear styling for a specific line
    void clear_line_styles(size_t line);

    // === Events & Hooks ===

    using BufferEventCallback = std::function<void(const BufferEventData&)>;

    /// Register a callback for buffer events
    void on_buffer_event(BufferEventCallback callback);

    /// Get the language/file type of this buffer
    [[nodiscard]] const std::string& language() const noexcept { return language_; }

    /// Set the language/file type (triggers LanguageChanged event)
    void set_language(std::string lang);

    /// Auto-detect language from file path
    static std::string detect_language(const std::filesystem::path& path);

    // === Undo/Redo ===

    /// Undo the last change
    bool undo(Position& out_cursor);

    /// Redo the last undone change
    bool redo(Position& out_cursor);

    /// Check if undo is available
    [[nodiscard]] bool can_undo() const noexcept { return !undo_stack_.empty(); }

    /// Check if redo is available
    [[nodiscard]] bool can_redo() const noexcept { return !redo_stack_.empty(); }

    /// Save current state to undo stack (called automatically before changes)
    void save_undo_state(Position cursor);

    /// Clear redo stack (called when new change happens)
    void clear_redo_stack();

private:
    std::string name_;
    std::vector<std::string> lines_;
    std::optional<std::filesystem::path> file_path_;
    bool modified_;
    std::string language_;

    // Styling information: one vector of styled ranges per line
    std::vector<std::vector<StyledRange>> line_styles_;

    // Event callbacks
    std::vector<BufferEventCallback> event_callbacks_;

    // Undo/Redo stacks
    std::vector<UndoState> undo_stack_;
    std::vector<UndoState> redo_stack_;
    static constexpr size_t MAX_UNDO_LEVELS = 100;
    bool in_undo_redo_ = false; // Prevent saving state during undo/redo

    /// Ensure the buffer has at least one line
    void ensure_min_lines();

    /// Mark the buffer as modified
    void mark_modified();

    /// Ensure styles vector matches lines vector size
    void ensure_styles_size();

    /// Emit a buffer event to all registered callbacks
    void emit_event(BufferEvent event, size_t line = 0);
};

} // namespace lumacs