// Package themes installs archduino theme files into ~/.config/archduino/themes.
package themes

import (
	"bytes"
	"context"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"

	"gitlab.hive-brain.de/MDietermann/Archduino/internal/config"
	"gitlab.hive-brain.de/MDietermann/Archduino/internal/module"
)

type Module struct{ cfg config.ThemesConfig }

func New(cfg config.ThemesConfig) Module { return Module{cfg: cfg} }

type filePair struct{ src, dst string }
type state struct{ Missing []filePair }

func (Module) Meta() module.Meta {
	return module.Meta{ID: "themes", Name: "Colorscheme themes", Description: "Install archduino themes."}
}

func destRoot() (string, error) {
	h, err := os.UserHomeDir()
	if err != nil {
		return "", err
	}
	return filepath.Join(h, ".config", "archduino", "themes"), nil
}

func (m Module) Detect(ctx context.Context) (module.State, error) {
	dst, err := destRoot()
	if err != nil {
		return nil, err
	}
	var missing []filePair
	err = filepath.WalkDir(m.cfg.Source, func(p string, d fs.DirEntry, werr error) error {
		if werr != nil {
			return werr
		}
		if d.IsDir() {
			return nil
		}
		rel, _ := filepath.Rel(m.cfg.Source, p)
		target := filepath.Join(dst, rel)
		a, errA := os.ReadFile(p)
		if errA != nil {
			return errA
		}
		b, errB := os.ReadFile(target)
		if errB != nil || !bytes.Equal(a, b) {
			missing = append(missing, filePair{src: p, dst: target})
		}
		return nil
	})
	if err != nil {
		if os.IsNotExist(err) {
			return state{}, nil
		}
		return nil, err
	}
	return state{Missing: missing}, nil
}

func (m Module) Plan(ctx context.Context, cur module.State) (module.Plan, error) {
	s, _ := cur.(state)
	if len(s.Missing) == 0 {
		return module.Plan{}, nil
	}
	pairs := append([]filePair{}, s.Missing...)
	return module.Plan{Actions: []module.Action{{
		Description: fmt.Sprintf("copy %d theme files", len(pairs)),
		Kind:        module.ActionFileWrite,
		Exec: func(ctx context.Context) error {
			for _, fp := range pairs {
				if err := os.MkdirAll(filepath.Dir(fp.dst), 0o755); err != nil {
					return err
				}
				data, err := os.ReadFile(fp.src)
				if err != nil {
					return err
				}
				if err := os.WriteFile(fp.dst, data, 0o644); err != nil {
					return err
				}
			}
			return nil
		},
	}}}, nil
}

func (m Module) Apply(ctx context.Context, p module.Plan, r module.Reporter) error {
	for i, a := range p.Actions {
		r.Progress(m.Meta().ID, i+1, len(p.Actions), a.Description)
		if err := a.Exec(ctx); err != nil {
			return err
		}
	}
	return nil
}

func (m Module) Verify(ctx context.Context) error {
	st, err := m.Detect(ctx)
	if err != nil {
		return err
	}
	if miss := st.(state).Missing; len(miss) > 0 {
		return fmt.Errorf("themes still missing: %d files", len(miss))
	}
	return nil
}