//    Copyright (C) 2020 Jakub Melka
//
//    This file is part of PdfForQt.
//
//    PdfForQt is free software: you can redistribute it and/or modify
//    it under the terms of the GNU Lesser General Public License as published by
//    the Free Software Foundation, either version 3 of the License, or
//    (at your option) any later version.
//
//    PdfForQt is distributed in the hope that it will be useful,
//    but WITHOUT ANY WARRANTY; without even the implied warranty of
//    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
//    GNU Lesser General Public License for more details.
//
//    You should have received a copy of the GNU Lesser General Public License
//    along with PDFForQt. If not, see <https://www.gnu.org/licenses/>.

#ifndef PDFFORM_H
#define PDFFORM_H

#include "pdfobject.h"
#include "pdfannotation.h"

#include <optional>

namespace pdf
{

class PDFObjectStorage;
class PDFFormField;

using PDFFormFieldPointer = QSharedPointer<PDFFormField>;
using PDFFormFields = std::vector<PDFFormFieldPointer>;

/// A simple proxy to the widget annotation
class PDFFormWidget
{
public:
    explicit inline PDFFormWidget() = default;
    explicit inline PDFFormWidget(PDFObjectReference widget, PDFFormField* parentField);

    PDFObjectReference getWidget() const { return m_widget; }
    PDFFormField* getParent() const { return m_parentField; }

    /// Parses form widget from the object reference. If some error occurs
    /// then empty object is returned, no exception is thrown.
    /// \param storage Storage
    /// \param reference Widget reference
    /// \param parentField Parent field
    static PDFFormWidget parse(const PDFObjectStorage* storage, PDFObjectReference reference, PDFFormField* parentField);

private:
    PDFObjectReference m_widget;
    PDFFormField* m_parentField;
};

using PDFFormWidgets = std::vector<PDFFormWidget>;

/// Form field is terminal or non-terminal field (non-terminal fields
/// have children), fields represents various interactive widgets, such as
/// checks, radio buttons, text edits etc., which are editable and user
/// can interact with them.
class PDFFormField
{
public:
    explicit inline PDFFormField() = default;

    enum class FieldType
    {
        Invalid,
        Button,
        Text,
        Choice,
        Signature
    };

    enum NameType
    {
        Partial,            ///< Partial name for this field
        UserCaption,        ///< Name used in GUI (for example, in message boxes)
        FullyQualified,     ///< Fully qualified name (according to the PDF specification 1.7)
        Export,             ///< Name for export
        NameTypeEnd
    };

    using FieldNames = std::array<QString, NameTypeEnd>;

    enum FieldFlag
    {
        None = 0,

        /// Field is read only, it doesn't respond on mouse clicks (if it is a button),
        /// associated widget annotation will not interact with the user. Field can't
        /// change it's value. Mainly used for calculable fields.
        ReadOnly = 1 << 0,

        /// If set, field is required, when submitting form by submit action. If submit
        /// action is triggered, then all fields with this flag must have a value.
        Required = 1 << 1,

        /// If set, field value must not be exported by submit form action.
        NoExport = 1 << 2,

        /// Text fields only. If set, then text can span multiple lines. Otherwise,
        /// text is restricted to single line.
        Multiline = 1 << 12,

        /// Text fields only. If set, field is intended to display text edit, which
        /// can edit passwords. Password characters should not be echoed to the screen
        /// and value of this field should not be stored in PDF file.
        Password = 1 << 13,

        /// Only for radio buttons. If set, at least one radio button is checked.
        /// If user clicks on checked radio button, it is not checked off. Otherwise
        /// user can uncheck checked radio button (so no button is selected).
        NoToggleToOff = 1 << 14,

        /// Valid only for buttons which have PushButton flag unset. If Radio flag is set,
        /// then widget is radio button, otherwise widget is push button.
        Radio = 1 << 15,

        /// Valid only for buttons. If set, button is push button.
        PushButton = 1 << 16,

        /// For choice fields only. If set, choice field is combo box.
        /// If clear, it is a list box.
        Combo = 1 << 17,

        /// For choice fields combo boxes only. If set, combo box is editable,
        /// i.e. user can enter custom text. If this flag is cleared, then combo box
        /// is not editable and user can only select items from the drop down list.
        Edit = 1 << 18,

        /// For choice fields only. If set, the field option's items should be sorted
        /// alphabetically, but not by the viewer application, but by author of the form.
        /// Viewer application should respect Opt array and display items in that order.
        Sort = 1 << 19,

        /// Text fields only. Text field is used to select file path, whose contents
        /// should be submitted as the value of the field.
        FileSelect = 1 << 20,

        /// For choice fields only. If set, then user can select multiple choices
        /// simultaneously, if clear, then only one item should be selected at the time.
        MultiSelect = 1 << 21,

        /// Text fields only. If set, texts entered in this field should not be spell checked.
        DoNotSpellcheck = 1 << 22,

        /// Text fields only. Allow only so much text, which fits field's area. If field's area is filled,
        /// then do not allow the user to store more text in the field.
        DoNotScroll = 1 << 23,

        /// Text fields only. If set, then MaxLen entry and annotation rectangle is used
        /// to divide space equally for each character. Text is laid out into those spaces.
        Comb = 1 << 24,

        /// Valid only for radio buttons. Radio buttons in a group of radio buttons,
        /// which have same value for 'On' state, will turn On and Off in unison, if one
        /// is checked, all are checked. If clear, radio buttons are mutually exclusive.
        RadiosInUnison = 1 << 25,

        /// Text fields only. Value of this field should be a rich text.
        RichText = 1 << 25,

        /// Choice fields only. If set, then when user selects choice by mouse,
        /// data is immediately commited. Otherwise data are commited only, when
        /// widget lose focus.
        CommitOnSelectionChange = 1 << 26
    };

    Q_DECLARE_FLAGS(FieldFlags, FieldFlag)

    PDFObjectReference getSelfReference() const { return m_selfReference; }
    FieldType getFieldType() const { return m_fieldType; }
    const PDFFormField* getParentField() const { return m_parentField; }
    const PDFFormFields& getChildFields() const { return m_childFields; }
    const PDFFormWidgets& getWidgets() const { return m_widgets; }
    const QString& getName(NameType nameType) const { return m_fieldNames.at(nameType); }
    FieldFlags getFlags() const { return m_fieldFlags; }
    const PDFObject& getValue() const { return m_value; }
    const PDFObject& getDefaultValue() const { return m_defaultValue; }

    /// Parses form field from the object reference. If some error occurs
    /// then null pointer is returned, no exception is thrown.
    /// \param storage Storage
    /// \param reference Field reference
    /// \param parentField Parent field (or nullptr, if it is root field)
    static PDFFormFieldPointer parse(const PDFObjectStorage* storage, PDFObjectReference reference, PDFFormField* parentField);

protected:
    PDFObjectReference m_selfReference;
    FieldType m_fieldType = FieldType::Invalid;
    PDFFormField* m_parentField = nullptr;
    PDFFormFields m_childFields;
    PDFFormWidgets m_widgets;
    FieldNames m_fieldNames;
    FieldFlags m_fieldFlags = None;
    PDFObject m_value;
    PDFObject m_defaultValue;
    PDFAnnotationAdditionalActions m_additionalActions;
};

/// Represents pushbutton, checkbox and radio button (which is distinguished
/// by flags).
class PDFFormFieldButton : public PDFFormField
{
public:
    explicit inline PDFFormFieldButton() = default;

    enum class ButtonType
    {
        PushButton,
        RadioButton,
        CheckBox
    };

    /// Determines button type from form field's flags
    ButtonType getButtonType() const;

    const QStringList& getOptions() const { return m_options; }

private:
    friend static PDFFormFieldPointer PDFFormField::parse(const PDFObjectStorage* storage, PDFObjectReference reference, PDFFormField* parentField);

    /// List of names of 'On' state for radio buttons. In widget annotation's appearance
    /// dictionaries, state names are computer generated numbers (for example /1, /3, ...),
    /// which are indices to this string list. This allows to distinguish between
    /// different widget annotations, even if they have same value in m_options array.
    QStringList m_options;
};

class PDFFormFieldText : public PDFFormField
{
public:
    explicit inline PDFFormFieldText() = default;

    PDFInteger getTextMaximalLength() const { return m_maxLength; }

private:
    friend static PDFFormFieldPointer PDFFormField::parse(const PDFObjectStorage* storage, PDFObjectReference reference, PDFFormField* parentField);

    /// Maximal length of text in the field. If zero,
    /// no maximal length is specified.
    PDFInteger m_maxLength = 0;
};

class PDFFormFieldChoice : public PDFFormField
{
public:
    explicit inline PDFFormFieldChoice() = default;

private:
    friend static PDFFormFieldPointer PDFFormField::parse(const PDFObjectStorage* storage, PDFObjectReference reference, PDFFormField* parentField);

};

class PDFFormFieldSignature : public PDFFormField
{
public:
    explicit inline PDFFormFieldSignature() = default;

private:
    friend static PDFFormFieldPointer PDFFormField::parse(const PDFObjectStorage* storage, PDFObjectReference reference, PDFFormField* parentField);

};

/// This class represents interactive form. Interactive form fields can span multiple
/// document pages. So this object represents all interactive form fields in the document.
/// Fields forms tree-like structure, where leafs are usually widgets. Fields include
/// ordinary widgets, such as buttons, check boxes, combo boxes and text fields, and one
/// special - signature field, which represents digital signature.
class PDFForm
{
public:
    explicit inline PDFForm() = default;

    enum class FormType
    {
        None,
        AcroForm,
        XFAForm
    };

    enum SignatureFlag
    {
        None            = 0x0000,
        SignatureExists = 0x0001, ///< If set, at least one signature exists in the document
        AppendOnly      = 0x0002, ///< If set, signature may be invalidated during rewrite
    };
    Q_DECLARE_FLAGS(SignatureFlags, SignatureFlag)

    const PDFFormFields& getFormFields() const { return m_formFields; }
    bool isAppearanceUpdateNeeded() const { return m_needAppearances; }
    SignatureFlags getSignatureFlags() const { return m_signatureFlags; }
    const std::vector<PDFObjectReference>& getCalculationOrder() const { return m_calculationOrder; }
    const PDFObject& getResources() const { return m_resources; }
    const std::optional<QByteArray>& getDefaultAppearance() const { return m_defaultAppearance; }
    const std::optional<PDFInteger>& getQuadding() const { return m_quadding; }
    const PDFObject& getXFA() const { return m_xfa; }

    /// Parses form from the object. If some error occurs
    /// then empty form is returned, no exception is thrown.
    /// \param storage Storage
    /// \param reference Field reference
    static PDFForm parse(const PDFObjectStorage* storage, PDFObject object);

private:
    FormType m_formType = FormType::None;
    PDFFormFields m_formFields;
    bool m_needAppearances = false;
    SignatureFlags m_signatureFlags = None;
    std::vector<PDFObjectReference> m_calculationOrder;
    PDFObject m_resources;
    std::optional<QByteArray> m_defaultAppearance;
    std::optional<PDFInteger> m_quadding;
    PDFObject m_xfa;
};

}   // namespace pdf

#endif // PDFFORM_H