#pragma once

#include <cstddef>
#include <cstdint>
#include <memory>
#include <stdexcept>
#include <string>
#include <vector>

struct ikv_node_t;

namespace ikv {

/// Runtime value types exposed by iKv.
enum ValueType {
    nullValue = 0,
    stringValue,
    intValue,
    realValue,
    booleanValue,
    objectValue,
    arrayValue
};

/// On-disk iKv format versions supported for explicit writes.
enum class Version : unsigned { v1 = 1, v2 = 2 };

/// Error raised for invalid types, unsupported operations, parse failures,
/// and I/O failures.
class Error : public std::runtime_error {
public:
    using std::runtime_error::runtime_error;
};

/// RAII handle to an iKv root or a node owned by an iKv tree.
///
/// Copies share ownership of the same tree. Child handles remain valid while their
/// node exists, but should be reacquired after replacing that node or refreshing the root.
class Value {
public:
    using ArrayIndex = std::uint32_t;

    /// Creates an object or array root. Scalar roots are not supported by iKv.
    explicit Value(ValueType type = objectValue, std::string root_name = "root");
    Value(const Value&) = default;

    /// Structural assignment is unavailable because iKv cannot clone arbitrary subtrees.
    Value& operator=(const Value&) = delete;

    /// Parses auto-detected iKv1 or iKv2 text.
    static Value parse(const std::string& text);

    /// Loads an auto-detected iKv1 or iKv2 text file.
    static Value load(const std::string& path);

    /// Parses an iKv binary buffer. The resulting tree owns any required data.
    static Value fromBinary(const void* data, std::size_t size);

    /// Loads an auto-detected binary iKv file.
    static Value loadBinary(const std::string& path);

    /// Returns the node's runtime type, or nullValue for a missing member.
    ValueType type() const noexcept;
    bool isNull() const noexcept;
    bool isString() const noexcept;
    bool isInt() const noexcept;
    bool isDouble() const noexcept;
    bool isBool() const noexcept;
    bool isObject() const noexcept;
    bool isArray() const noexcept;
    bool empty() const;
    std::size_t size() const;
    std::string name() const;

    bool isMember(const std::string& key) const;

    /// Looks up an object member. A missing non-const member returns an assignable null Value.
    Value operator[](const std::string& key);
    Value operator[](const char* key);
    Value operator[](const std::string& key) const;
    Value operator[](const char* key) const;
    Value operator[](ArrayIndex index);
    Value operator[](int index);
    Value operator[](ArrayIndex index) const;
    Value operator[](int index) const;

    /// Returns an object member or a shared copy of fallback when the key is absent.
    Value get(const std::string& key, const Value& fallback) const;

    /// Assigns a scalar to an object member returned by operator[].
    Value& operator=(const std::string& value);
    Value& operator=(const char* value);
    Value& operator=(std::int64_t value);
    Value& operator=(int value);
    Value& operator=(double value);
    Value& operator=(bool value);

    /// Adds or replaces an object member and returns a handle to it.
    Value makeObject(const std::string& key);

    /// Adds an array member. nullValue creates an untyped array.
    Value makeArray(const std::string& key, ValueType element_type = nullValue);

    /// Appends to an array. Typed arrays reject incompatible values with Error.
    Value append(const std::string& value);
    Value append(const char* value);
    Value append(std::int64_t value);
    Value append(int value);
    Value append(double value);
    Value append(bool value);
    Value appendObject();

    std::string asString() const;
    std::int64_t asInt64() const;
    int asInt() const;
    double asDouble() const;
    bool asBool() const;

    /// Writes text or binary output, using iKv2 unless a version is specified.
    void write(const std::string& path, Version version = Version::v2) const;
    void writeBinary(const std::string& path, Version version = Version::v2) const;
    std::vector<std::uint8_t> toBinary(Version version = Version::v2) const;

    /// Replaces this root in place from a text or binary path while preserving shared handles.
    /// Only mutable root Values can be refreshed; failure leaves the existing tree unchanged.
    void refresh(const std::string& path);

private:
    struct Deleter { void operator()(ikv_node_t* node) const noexcept; };
    using Owner = std::shared_ptr<ikv_node_t>;

    Value(Owner owner, ikv_node_t* node, ikv_node_t* parent, std::string key, bool read_only = false);
    static Value adopt(ikv_node_t* node);
    void require(ValueType expected, const char* operation) const;
    void requireMutable(const char* operation) const;
    void requireObjectParent(const char* operation) const;
    Value appended(std::size_t old_size);

    Owner owner_;
    ikv_node_t* node_ = nullptr;
    ikv_node_t* parent_ = nullptr;
    std::string key_;
    bool read_only_ = false;
};

} // namespace ikv