// Copyright (C) 2026 Petr Mironychev
// SPDX-License-Identifier: GPL-3.0-or-later
// Additional attribution terms under GPLv3 §7(b) apply — see LICENSE

#include "session/HistoryProjection.hpp"

#include <optional>
#include <utility>

#if defined(Q_CC_MSVC)
#pragma warning(error : 4062)
#else
#pragma GCC diagnostic error "-Wswitch"
#endif

namespace QodeAssist::Session {

namespace {

QString signatureSuffix(const QString &signature)
{
    return QString("\n[Signature: %1...]").arg(signature.left(40));
}

QString redactedThinkingText()
{
    return QStringLiteral("[Thinking content redacted by safety systems]");
}

QString thinkingDisplayText(const ThinkingBlock &block)
{
    const QString text = block.redacted && block.text.isEmpty() ? redactedThinkingText()
                                                                : block.text;
    return block.signature.isEmpty() ? text : text + signatureSuffix(block.signature);
}

QString thinkingTextOf(const MessageRow &row)
{
    QString text = row.content;
    if (!row.signature.isEmpty()) {
        const QString suffix = signatureSuffix(row.signature);
        if (text.endsWith(suffix))
            text.chop(suffix.size());
    }

    if (row.redacted && text == redactedThinkingText())
        return {};

    return text;
}

QString toolDisplayText(const ToolCallBlock &block)
{
    if (block.name.isEmpty())
        return block.result;
    return block.result.isEmpty() ? block.name : block.name + "\n" + block.result;
}

ToolCallBlock toolCallOf(const MessageRow &row)
{
    ToolCallBlock block{
        row.id,
        row.toolName,
        row.toolArguments,
        row.toolResult,
        row.toolKind,
        restoredToolStatus(row.toolStatus),
        row.toolDetails,
        row.kind == RowKind::AgentTool};
    if (block.name.isEmpty() && block.result.isEmpty())
        block.result = row.content;
    return block;
}

RowKind textRowKind(MessageRole role)
{
    switch (role) {
    case MessageRole::System:
        return RowKind::System;
    case MessageRole::User:
        return RowKind::User;
    case MessageRole::Assistant:
        return RowKind::Assistant;
    }
    return RowKind::Assistant;
}

} // namespace

bool isTerminalToolStatus(const QString &status)
{
    return status.isEmpty() || status == QLatin1String("completed")
           || status == QLatin1String("failed") || status == QLatin1String("interrupted");
}

QString restoredToolStatus(QString status)
{
    if (!isTerminalToolStatus(status))
        return QStringLiteral("interrupted");
    return status;
}

bool isTranscriptOnlyRow(RowKind kind)
{
    switch (kind) {
    case RowKind::AgentTool:
    case RowKind::FileEdit:
    case RowKind::Permission:
    case RowKind::Plan:
        return true;
    case RowKind::User:
    case RowKind::Assistant:
    case RowKind::System:
    case RowKind::Tool:
    case RowKind::Thinking:
        return false;
    }
    return false;
}

RowTreatment rowTreatmentFor(RowAudience audience, RowKind kind)
{
    switch (audience) {
    case RowAudience::Prompt:
        switch (kind) {
        case RowKind::User:
            return RowTreatment::UserText;
        case RowKind::Assistant:
        case RowKind::System:
            return RowTreatment::AssistantText;
        case RowKind::Thinking:
            return RowTreatment::AssistantThinking;
        case RowKind::Tool:
            return RowTreatment::ToolExchange;
        case RowKind::AgentTool:
        case RowKind::FileEdit:
        case RowKind::Permission:
        case RowKind::Plan:
            return RowTreatment::Omit;
        }
        break;
    case RowAudience::Compression:
        switch (kind) {
        case RowKind::User:
            return RowTreatment::UserText;
        case RowKind::Assistant:
        case RowKind::System:
            return RowTreatment::AssistantText;
        case RowKind::Thinking:
        case RowKind::Tool:
        case RowKind::AgentTool:
        case RowKind::FileEdit:
        case RowKind::Permission:
        case RowKind::Plan:
            return RowTreatment::Omit;
        }
        break;
    case RowAudience::TokenCount:
        return rowTreatmentFor(RowAudience::Prompt, kind);
    }
    return RowTreatment::Omit;
}

std::optional<MessageRow> projectBlockToRow(const Message &message, const ContentBlock &block)
{
    static_assert(
        std::variant_size_v<ContentBlock> == 8,
        "ContentBlock gained an alternative; extend the projection below or the block lives in the "
        "history without ever rendering");

    if (const auto *text = std::get_if<TextBlock>(&block)) {
        MessageRow row;
        row.kind = textRowKind(message.role);
        row.id = message.id;
        row.content = text->text;
        return row;
    }

    if (const auto *thinking = std::get_if<ThinkingBlock>(&block)) {
        MessageRow row;
        row.kind = RowKind::Thinking;
        row.id = message.id;
        row.content = thinkingDisplayText(*thinking);
        row.redacted = thinking->redacted;
        row.signature = thinking->signature;
        return row;
    }

    if (const auto *tool = std::get_if<ToolCallBlock>(&block)) {
        MessageRow row;
        row.kind = tool->fromAgent ? RowKind::AgentTool : RowKind::Tool;
        row.id = tool->id;
        row.content = toolDisplayText(*tool);
        row.toolName = tool->name;
        row.toolArguments = tool->arguments;
        row.toolResult = tool->result;
        row.toolKind = tool->kind;
        row.toolStatus = tool->status;
        row.toolDetails = tool->details;
        return row;
    }

    if (const auto *edit = std::get_if<FileEditBlock>(&block)) {
        MessageRow row;
        row.kind = RowKind::FileEdit;
        row.id = edit->id;
        row.content = edit->payload;
        return row;
    }

    if (const auto *permission = std::get_if<PermissionBlock>(&block)) {
        MessageRow row;
        row.kind = RowKind::Permission;
        row.id = permission->requestId;
        row.content = encodePermissionBlock(*permission);
        return row;
    }

    if (const auto *plan = std::get_if<PlanBlock>(&block)) {
        MessageRow row;
        row.kind = RowKind::Plan;
        row.id = message.id;
        row.content = encodePlanBlock(*plan);
        return row;
    }

    return std::nullopt;
}

QList<MessageRow> projectMessageToRows(const Message &message)
{
    QList<MessageRow> rows;

    bool usageAssigned = message.usage.isEmpty();
    qsizetype textRowIndex = -1;

    auto appendRow = [&](MessageRow row) {
        if (!usageAssigned && row.id == message.id && !isTranscriptOnlyRow(row.kind)) {
            row.usage = message.usage;
            usageAssigned = true;
        }
        rows.append(std::move(row));
        return rows.size() - 1;
    };

    auto ensureTextRow = [&] {
        if (textRowIndex < 0) {
            MessageRow row;
            row.kind = textRowKind(message.role);
            row.id = message.id;
            textRowIndex = appendRow(row);
        }
        return textRowIndex;
    };

    for (const ContentBlock &block : message.blocks) {
        if (auto row = projectBlockToRow(message, block)) {
            const qsizetype index = appendRow(std::move(*row));
            if (std::holds_alternative<TextBlock>(block))
                textRowIndex = index;
        } else if (const auto *attachment = std::get_if<AttachmentBlock>(&block)) {
            rows[ensureTextRow()].attachments.append(*attachment);
        } else if (const auto *image = std::get_if<ImageBlock>(&block)) {
            rows[ensureTextRow()].images.append(*image);
        }
    }

    return rows;
}

QList<MessageRow> projectToRows(const ConversationHistory &history)
{
    QList<MessageRow> rows;

    for (const Message &message : history.messages())
        rows.append(projectMessageToRows(message));

    return rows;
}

ConversationHistory buildFromRows(const QList<MessageRow> &rows)
{
    ConversationHistory history;
    std::optional<Message> assistant;

    auto flush = [&] {
        if (assistant) {
            history.append(*assistant);
            assistant.reset();
        }
    };

    auto openAssistant = [&]() -> Message & {
        if (!assistant) {
            Message message;
            message.role = MessageRole::Assistant;
            assistant = message;
        }
        return *assistant;
    };

    for (const MessageRow &row : rows) {
        switch (row.kind) {
        case RowKind::User:
        case RowKind::System: {
            flush();
            Message message;
            message.role = row.kind == RowKind::User ? MessageRole::User : MessageRole::System;
            message.id = row.id;
            message.usage = row.usage;
            message.blocks.append(TextBlock{row.content});
            for (const AttachmentBlock &attachment : row.attachments)
                message.blocks.append(attachment);
            for (const ImageBlock &image : row.images)
                message.blocks.append(image);
            history.append(message);
            break;
        }
        case RowKind::Assistant:
        case RowKind::Thinking: {
            if (assistant && !row.id.isEmpty() && !assistant->id.isEmpty()
                && assistant->id != row.id) {
                flush();
            }
            Message &message = openAssistant();
            if (message.id.isEmpty())
                message.id = row.id;
            if (row.kind == RowKind::Assistant) {
                message.blocks.append(TextBlock{row.content});
            } else {
                message.blocks.append(
                    ThinkingBlock{thinkingTextOf(row), row.signature, row.redacted});
            }
            if (!row.usage.isEmpty())
                message.usage = row.usage;
            break;
        }
        case RowKind::Tool:
        case RowKind::AgentTool: {
            Message &message = openAssistant();
            message.blocks.append(toolCallOf(row));
            break;
        }
        case RowKind::FileEdit: {
            Message &message = openAssistant();
            message.blocks.append(FileEditBlock{row.id, row.content});
            break;
        }
        case RowKind::Permission: {
            Message &message = openAssistant();
            if (auto permission = decodePermissionBlock(row.content))
                message.blocks.append(restoredPermissionBlock(*permission));
            else
                message.blocks.append(TextBlock{row.content});
            break;
        }
        case RowKind::Plan: {
            Message &message = openAssistant();
            if (message.id.isEmpty())
                message.id = row.id;
            if (!row.usage.isEmpty())
                message.usage = row.usage;
            if (auto plan = decodePlanBlock(row.content))
                message.blocks.append(*plan);
            else
                message.blocks.append(TextBlock{row.content});
            break;
        }
        }
    }

    flush();

    return history;
}

} // namespace QodeAssist::Session