// GUITheme.h — ImGui theming helpers and background mode
#pragma once

#include <imgui.h>
#include <vector>
#include <memory>
#include <string>
#include <cstddef>
#include <algorithm>
#include <cctype>

#include "themes/ThemeHelpers.h"

namespace kte {
// Background mode selection for light/dark palettes
enum class BackgroundMode { Light, Dark };

// Global background mode; default to Dark to match prior defaults
static inline auto gBackgroundMode = BackgroundMode::Dark;

// Basic theme identifier (kept minimal; some ids are aliases)
enum class ThemeId {
	EInk = 0,
	GruvboxDarkMedium = 1,
	GruvboxLightMedium = 1, // alias to unified gruvbox index
	Nord = 2,
	Plan9 = 3,
	Solarized = 4,
};

// Current theme tracking
static inline auto gCurrentTheme             = ThemeId::Nord;
static inline std::size_t gCurrentThemeIndex = 0;

// Forward declarations for helpers used below
static size_t ThemeIndexFromId(ThemeId id);

static ThemeId ThemeIdFromIndex(size_t idx);

// Helpers to set/query background mode
static void
SetBackgroundMode(const BackgroundMode m)
{
	gBackgroundMode = m;
}


static BackgroundMode
GetBackgroundMode()
{
	return gBackgroundMode;
}


static inline const char *
BackgroundModeName()
{
	return gBackgroundMode == BackgroundMode::Light ? "light" : "dark";
}


// Include individual theme implementations split under ./themes
#include "themes/Nord.h"
#include "themes/Plan9.h"
#include "themes/Solarized.h"
#include "themes/Gruvbox.h"
#include "themes/EInk.h"


// Theme abstraction and registry (generalized theme system)
class Theme {
public:
	virtual ~Theme() = default;

	[[nodiscard]] virtual const char *Name() const = 0; // canonical name (e.g., "nord", "gruvbox-dark")
	virtual void Apply() const = 0; // apply to current ImGui style
	virtual ThemeId Id() = 0; // theme identifier
};

namespace detail {
struct NordTheme final : Theme {
	[[nodiscard]] const char *Name() const override
	{
		return "nord";
	}


	void Apply() const override
	{
		ApplyNordImGuiTheme();
	}


	ThemeId Id() override
	{
		return ThemeId::Nord;
	}
};

struct GruvboxTheme final : Theme {
	[[nodiscard]] const char *Name() const override
	{
		return "gruvbox";
	}


	void Apply() const override
	{
		if (gBackgroundMode == BackgroundMode::Light)
			ApplyGruvboxLightMediumTheme();
		else
			ApplyGruvboxDarkMediumTheme();
	}


	ThemeId Id() override
	{
		// Legacy maps to dark; unified under base id GruvboxDarkMedium
		return ThemeId::GruvboxDarkMedium;
	}
};

struct EInkTheme final : Theme {
	[[nodiscard]] const char *Name() const override
	{
		return "eink";
	}


	void Apply() const override
	{
		if (gBackgroundMode == BackgroundMode::Dark)
			ApplyEInkDarkImGuiTheme();
		else
			ApplyEInkImGuiTheme();
	}


	ThemeId Id() override
	{
		return ThemeId::EInk;
	}
};

struct SolarizedTheme final : Theme {
	[[nodiscard]] const char *Name() const override
	{
		return "solarized";
	}


	void Apply() const override
	{
		if (gBackgroundMode == BackgroundMode::Light)
			ApplySolarizedLightTheme();
		else
			ApplySolarizedDarkTheme();
	}


	ThemeId Id() override
	{
		return ThemeId::Solarized;
	}
};

struct Plan9Theme final : Theme {
	[[nodiscard]] const char *Name() const override
	{
		return "plan9";
	}


	void Apply() const override
	{
		ApplyPlan9Theme();
	}


	ThemeId Id() override
	{
		return ThemeId::Plan9;
	}
};
} // namespace detail

static const std::vector<std::unique_ptr<Theme> > &
ThemeRegistry()
{
	static std::vector<std::unique_ptr<Theme> > reg;
	if (reg.empty()) {
		// Alphabetical by canonical name: eink, gruvbox, nord, plan9, solarized
		reg.emplace_back(std::make_unique<detail::EInkTheme>());
		reg.emplace_back(std::make_unique<detail::GruvboxTheme>());
		reg.emplace_back(std::make_unique<detail::NordTheme>());
		reg.emplace_back(std::make_unique<detail::Plan9Theme>());
		reg.emplace_back(std::make_unique<detail::SolarizedTheme>());
	}
	return reg;
}


// Canonical theme name for a given ThemeId (via registry order)
[[maybe_unused]] static const char *
ThemeName(const ThemeId id)
{
	const auto &reg  = ThemeRegistry();
	const size_t idx = ThemeIndexFromId(id);
	if (idx < reg.size())
		return reg[idx]->Name();
	return "unknown";
}


// Helper to apply a theme by id and update current theme
static void
ApplyTheme(const ThemeId id)
{
	const auto &reg  = ThemeRegistry();
	const size_t idx = ThemeIndexFromId(id);
	if (idx < reg.size()) {
		reg[idx]->Apply();
		gCurrentTheme      = id;
		gCurrentThemeIndex = idx;
	}
}


[[maybe_unused]] static ThemeId
CurrentTheme()
{
	return gCurrentTheme;
}


// Cycle helpers
[[maybe_unused]] static ThemeId
NextTheme()
{
	const auto &reg = ThemeRegistry();
	if (reg.empty()) {
		return gCurrentTheme;
	}

	const size_t nxt = (gCurrentThemeIndex + 1) % reg.size();
	ApplyTheme(ThemeIdFromIndex(nxt));
	return gCurrentTheme;
}


[[maybe_unused]] static ThemeId
PrevTheme()
{
	const auto &reg = ThemeRegistry();
	if (reg.empty()) {
		return gCurrentTheme;
	}

	const size_t prv = (gCurrentThemeIndex + reg.size() - 1) % reg.size();
	ApplyTheme(ThemeIdFromIndex(prv));
	return gCurrentTheme;
}


// Name-based API
[[maybe_unused]] static const Theme *
GetThemeByName(const std::string &name)
{
	const auto &reg = ThemeRegistry();
	for (const auto &t: reg) {
		if (name == t->Name())
			return t.get();
	}

	return nullptr;
}


[[maybe_unused]] static bool
ApplyThemeByName(const std::string &name)
{
	// Handle aliases and background-specific names
	std::string n = name;
	// lowercase copy
	std::transform(n.begin(), n.end(), n.begin(), [](unsigned char c) {
		return static_cast<char>(std::tolower(c));
	});

	if (n == "gruvbox-dark") {
		SetBackgroundMode(BackgroundMode::Dark);
		n = "gruvbox";
	} else if (n == "gruvbox-light") {
		SetBackgroundMode(BackgroundMode::Light);
		n = "gruvbox";
	} else if (n == "solarized-dark") {
		SetBackgroundMode(BackgroundMode::Dark);
		n = "solarized";
	} else if (n == "solarized-light") {
		SetBackgroundMode(BackgroundMode::Light);
		n = "solarized";
	} else if (n == "eink-dark") {
		SetBackgroundMode(BackgroundMode::Dark);
		n = "eink";
	} else if (n == "eink-light") {
		SetBackgroundMode(BackgroundMode::Light);
		n = "eink";
	}

	const auto &reg = ThemeRegistry();
	for (size_t i = 0; i < reg.size(); ++i) {
		if (n == reg[i]->Name()) {
			reg[i]->Apply();
			gCurrentThemeIndex = i;
			gCurrentTheme      = ThemeIdFromIndex(i);
			return true;
		}
	}

	return false;
}


[[maybe_unused]] static const char *
CurrentThemeName()
{
	const auto &reg = ThemeRegistry();
	if (gCurrentThemeIndex < reg.size()) {
		return reg[gCurrentThemeIndex]->Name();
	}

	return "unknown";
}


// Helpers to map between legacy ThemeId and registry index
static size_t
ThemeIndexFromId(const ThemeId id)
{
	switch (id) {
	case ThemeId::EInk:
		return 0;
	case ThemeId::GruvboxDarkMedium:
		return 1;
	case ThemeId::Nord:
		return 2;
	case ThemeId::Plan9:
		return 3;
	case ThemeId::Solarized:
		return 4;
	}
	return 0;
}


static ThemeId
ThemeIdFromIndex(const size_t idx)
{
	switch (idx) {
	default:
	case 0:
		return ThemeId::EInk;
	case 1:
		return ThemeId::GruvboxDarkMedium; // unified gruvbox
	case 2:
		return ThemeId::Nord;
	case 3:
		return ThemeId::Plan9;
	case 4:
		return ThemeId::Solarized;
	}
}


// --- Syntax palette (v1): map TokenKind to ink color per current theme/background ---
[[maybe_unused]] static ImVec4
SyntaxInk(const TokenKind k)
{
	// Basic palettes for dark/light backgrounds; tuned for Nord-ish defaults
	const bool dark = (GetBackgroundMode() == BackgroundMode::Dark);
	// Base text
	const ImVec4 def = dark ? RGBA(0xD8DEE9) : RGBA(0x2E3440);
	switch (k) {
	case TokenKind::Keyword:
		return dark ? RGBA(0x81A1C1) : RGBA(0x5E81AC);
	case TokenKind::Type:
		return dark ? RGBA(0x8FBCBB) : RGBA(0x4C566A);
	case TokenKind::String:
		return dark ? RGBA(0xA3BE8C) : RGBA(0x6C8E5E);
	case TokenKind::Char:
		return dark ? RGBA(0xA3BE8C) : RGBA(0x6C8E5E);
	case TokenKind::Comment:
		return dark ? RGBA(0x616E88) : RGBA(0x7A869A);
	case TokenKind::Number:
		return dark ? RGBA(0xEBCB8B) : RGBA(0xB58900);
	case TokenKind::Preproc:
		return dark ? RGBA(0xD08770) : RGBA(0xAF3A03);
	case TokenKind::Constant:
		return dark ? RGBA(0xB48EAD) : RGBA(0x7B4B7F);
	case TokenKind::Function:
		return dark ? RGBA(0x88C0D0) : RGBA(0x3465A4);
	case TokenKind::Operator:
		return dark ? RGBA(0xECEFF4) : RGBA(0x2E3440);
	case TokenKind::Punctuation:
		return dark ? RGBA(0xECEFF4) : RGBA(0x2E3440);
	case TokenKind::Identifier:
		return def;
	case TokenKind::Whitespace:
		return def;
	case TokenKind::Error:
		return dark ? RGBA(0xBF616A) : RGBA(0xCC0000);
	case TokenKind::Default: default:
		return def;
	}
}
} // namespace kte