// Package config loads embedded defaults and optionally merges a user
// overlay from ~/.config/archduino/overlay.yaml.
package config

import (
	_ "embed"
	"fmt"
	"os"
	"path/filepath"

	"gopkg.in/yaml.v3"
)

//go:embed defaults.yaml
var defaultsYAML []byte

type Packages struct {
	Base []string `yaml:"base"`
}
type ArduinoCLIConfig struct {
	Version string   `yaml:"version"`
	URL     string   `yaml:"url"`
	Cores   []string `yaml:"cores"`
}
type ZshPlugin struct {
	Name string `yaml:"name"`
	Repo string `yaml:"repo"`
}
type ZshConfig struct {
	OhMyZshRepo string      `yaml:"oh_my_zsh_repo"`
	Plugins     []ZshPlugin `yaml:"plugins"`
}
type ZellijConfig struct {
	ConfigURL string `yaml:"config_url"`
}
type ThemesConfig struct {
	Source string `yaml:"source"`
}
type ShellConfigBlock struct {
	Name    string `yaml:"name"`
	File    string `yaml:"file"`
	Content string `yaml:"content"`
}
type ShellConfigSection struct {
	Blocks []ShellConfigBlock `yaml:"blocks"`
}

type NeovimConfig struct {
	NvChadStarterRepo string `yaml:"nvchad_starter_repo"`
}

type RenodePlatform struct {
	Name     string `yaml:"name"`
	ReplPath string `yaml:"repl_path"`
	Machine  string `yaml:"machine"`
}

type RenodeConfig struct {
	WokwiVersion string           `yaml:"wokwi_version"`
	WokwiURL     string           `yaml:"wokwi_url"`
	Platforms    []RenodePlatform `yaml:"platforms"`
}

type Board struct {
	Name     string `yaml:"name"`
	FQBN     string `yaml:"fqbn"`
	Template string `yaml:"template"`
}

type Scaffolding struct {
	Boards []Board `yaml:"boards"`
}

// Config is the fully-resolved runtime configuration.
type Config struct {
	Version         int                `yaml:"version"`
	ExtraPackages   []string           `yaml:"extra_packages"`
	DisabledModules []string           `yaml:"disabled_modules"`
	ThemeOverrides  map[string]string  `yaml:"theme_overrides"`
	Packages        Packages           `yaml:"packages"`
	Fonts           []string           `yaml:"fonts"`
	ArduinoCLI      ArduinoCLIConfig   `yaml:"arduino_cli"`
	Zsh             ZshConfig          `yaml:"zsh"`
	Zellij          ZellijConfig       `yaml:"zellij"`
	Themes          ThemesConfig       `yaml:"themes"`
	ShellConfig     ShellConfigSection `yaml:"shell_config"`
	Neovim          NeovimConfig       `yaml:"neovim"`
	Renode          RenodeConfig       `yaml:"renode"`
	Scaffolding     Scaffolding        `yaml:"scaffolding"`
}

const currentVersion = 1

// Load returns defaults merged with the overlay at overlayPath (if present).
// If overlayPath is "", the default location (~/.config/archduino/overlay.yaml)
// is used. A missing overlay is not an error.
func Load(overlayPath string) (Config, error) {
	var cfg Config
	if err := yaml.Unmarshal(defaultsYAML, &cfg); err != nil {
		return Config{}, fmt.Errorf("parse embedded defaults: %w", err)
	}

	if overlayPath == "" {
		home, err := os.UserHomeDir()
		if err != nil {
			return cfg, nil
		}
		overlayPath = filepath.Join(home, ".config", "archduino", "overlay.yaml")
	}

	data, err := os.ReadFile(overlayPath)
	if err != nil {
		if os.IsNotExist(err) {
			return cfg, nil
		}
		return Config{}, fmt.Errorf("read overlay %s: %w", overlayPath, err)
	}

	var overlay Config
	if err := yaml.Unmarshal(data, &overlay); err != nil {
		return Config{}, fmt.Errorf("parse overlay %s: %w", overlayPath, err)
	}
	if overlay.Version != 0 && overlay.Version != currentVersion {
		return Config{}, fmt.Errorf("overlay %s: unsupported version %d (want %d)", overlayPath, overlay.Version, currentVersion)
	}

	return merge(cfg, overlay), nil
}

func merge(base, over Config) Config {
	out := base
	if len(over.ExtraPackages) > 0 {
		out.ExtraPackages = append(append([]string{}, base.ExtraPackages...), over.ExtraPackages...)
	}
	if len(over.DisabledModules) > 0 {
		out.DisabledModules = append(append([]string{}, base.DisabledModules...), over.DisabledModules...)
	}
	if len(over.ThemeOverrides) > 0 {
		merged := make(map[string]string, len(base.ThemeOverrides)+len(over.ThemeOverrides))
		for k, v := range base.ThemeOverrides {
			merged[k] = v
		}
		for k, v := range over.ThemeOverrides {
			merged[k] = v
		}
		out.ThemeOverrides = merged
	}
	if len(over.Packages.Base) > 0 {
		out.Packages = over.Packages
	}
	if len(over.Fonts) > 0 {
		out.Fonts = over.Fonts
	}
	if over.ArduinoCLI.Version != "" {
		out.ArduinoCLI = over.ArduinoCLI
	}
	if over.Zsh.OhMyZshRepo != "" {
		out.Zsh = over.Zsh
	}
	if over.Zellij.ConfigURL != "" {
		out.Zellij = over.Zellij
	}
	if over.Themes.Source != "" {
		out.Themes = over.Themes
	}
	if len(over.ShellConfig.Blocks) > 0 {
		out.ShellConfig = over.ShellConfig
	}
	if over.Neovim.NvChadStarterRepo != "" {
		out.Neovim = over.Neovim
	}
	if over.Renode.WokwiVersion != "" || len(over.Renode.Platforms) > 0 {
		out.Renode = over.Renode
	}
	if len(over.Scaffolding.Boards) > 0 {
		out.Scaffolding = over.Scaffolding
	}
	return out
}