#ifndef OLLIE_CHAT_RENDERER_H
#define OLLIE_CHAT_RENDERER_H

#include <QString>
#include <QList>
#include <QStringList>
#include <QTextEdit>
#include <QRegularExpression>

namespace KSyntaxHighlighting {
    class Repository;
}

// Parsed chat block
struct ChatBlock {
    enum Type {
        User,
        Assistant,
        Reasoning,
        Call,
        Tool,
        Error,
        Info
    };

    Type type;
    QString name;    // tool/call name
    QString content; // raw text content
};

// Sub-block within a message (prose, code fence, diff)
struct SubBlock {
    enum Type { Prose, Code, Diff, Interrupt };

    Type type;
    QString language;
    QString fenceMeta; // extra text after language on the fence line (e.g., "/path:10-20")
    QString content;
};

/**
 * ChatRenderer parses ollie chat output into structured blocks
 * and renders them as styled HTML in a QTextEdit.
 *
 * To avoid performance degradation on long conversations, only a
 * tail window of blocks is eagerly rendered. Earlier blocks are
 * loaded on demand when the user scrolls up.
 */
class ChatRenderer
{
public:
    ChatRenderer();
    ~ChatRenderer();

    /// Set external diff storage. When set, diffs are stored here and
    /// rendered as clickable links rather than inline.
    void setDiffStorage(QStringList *storage) { m_diffStorage = storage; }

    /// Storage for apply-able code blocks. Each entry is the code content.
    /// Rendered with a clickable "Apply" link.
    struct ApplyBlock {
        QString filePath;
        QString code;
        int startLine = -1; // 1-indexed, inclusive. -1 = insert at cursor
        int endLine = -1;   // 1-indexed, inclusive. -1 = insert at cursor
    };
    void setApplyStorage(QList<ApplyBlock> *storage) { m_applyStorage = storage; }

    /// Maximum number of blocks to render eagerly (tail window).
    static constexpr int DefaultWindowSize = 40;
    void setWindowSize(int n) { m_windowSize = n; }
    int windowSize() const { return m_windowSize; }

    /// Parse raw chat text into blocks
    QList<ChatBlock> parseBlocks(const QString &text) const;

    /// Parse a block's content into sub-blocks (prose, code, diff)
    QList<SubBlock> parseSubBlocks(const QString &content) const;

    /// Render the tail window of blocks into the QTextEdit.
    /// Parses all blocks but only generates HTML for the last windowSize().
    void render(QTextEdit *view, const QString &rawText);

    /// Render incrementally: assumes rawText is the full text and only
    /// the tail has changed since last render. Returns true if it did
    /// an incremental update, false if it did a full re-render.
    bool renderIncremental(QTextEdit *view, const QString &rawText);

    /// Prepend older blocks into the view. Returns the number of
    /// blocks actually prepended (0 if all blocks are already shown).
    int prependOlder(QTextEdit *view, int count);

    /// True if there are older blocks not yet rendered.
    bool hasOlderBlocks() const { return m_renderStart > 0; }

    /// Total number of parsed blocks.
    int totalBlocks() const { return m_allBlocks.size(); }

    /// Number of blocks currently rendered.
    int renderedBlocks() const { return m_allBlocks.size() - m_renderStart; }

private:
    QString blockToHtml(const ChatBlock &block) const;
    QString subBlockToHtml(const SubBlock &sub, bool preserveWhitespace = false) const;
    QString highlightCode(const QString &code, const QString &language) const;
    QString renderDiff(const QString &diff) const;
    QString renderProse(const QString &prose) const;
    QString escapeHtml(const QString &text) const;

    KSyntaxHighlighting::Repository *m_repo;
    QStringList *m_diffStorage = nullptr;
    QList<ApplyBlock> *m_applyStorage = nullptr;
    QString m_lastRawText; // for incremental rendering
    int m_lastBlockCount = 0;

    // Windowed rendering state
    QList<ChatBlock> m_allBlocks; // all parsed blocks
    int m_renderStart = 0;        // index of first rendered block
    int m_windowSize = DefaultWindowSize;

    // Colors (derived from palette)
    mutable bool m_dark = false;
    void detectTheme() const;
};

#endif // OLLIE_CHAT_RENDERER_H