package meta

import (
	"encoding/json"
	"errors"
	"fmt"
	"io/fs"
	"os"
	"path/filepath"
	"strings"

	"go.jolheiser.com/eget/disk"
)

type Meta struct {
	Packages map[string]Package `json:"packages"`
}

type Package struct {
	Repo    string `json:"repo"`
	Version string `json:"version"`
}

func Upsert(name, repo, version string) error {
	m, err := Read()
	if err != nil {
		return err
	}
	for n := range m.Packages {
		if strings.EqualFold(n, name) {
			m.Packages[n] = Package{
				Repo:    repo,
				Version: version,
			}
			return save(m)
		}
	}
	m.Packages[name] = Package{
		Repo:    repo,
		Version: version,
	}
	return save(m)
}

func Read() (Meta, error) {
	m := Meta{
		Packages: make(map[string]Package),
	}
	fp := metaPath()
	fi, err := os.Open(fp)
	if err != nil {
		if errors.Is(err, fs.ErrNotExist) {
			return m, json.Unmarshal([]byte(`{}`), &m)
		}
		return m, fmt.Errorf("could not open meta file: %w", err)
	}
	defer fi.Close()

	if err := json.NewDecoder(fi).Decode(&m); err != nil {
		return m, fmt.Errorf("could not decode meta: %w", err)
	}
	return m, nil
}

func Remove(name string) error {
	m, err := Read()
	if err != nil {
		return err
	}
	for n := range m.Packages {
		if strings.EqualFold(n, name) {
			delete(m.Packages, name)
			return save(m)
		}
	}
	return fmt.Errorf("could not find package to remove for %q", name)
}

func metaPath() string {
	home, err := os.UserHomeDir()
	if err != nil {
		home = "."
	}
	return filepath.Join(home, ".eget", "packages.json")
}

func save(m Meta) error {
	fp := metaPath()
	fi, err := os.Create(fp)
	if err != nil {
		return fmt.Errorf("could not create meta file: %w", err)
	}
	if err := json.NewEncoder(fi).Encode(m); err != nil {
		return err
	}
	if err := fi.Close(); err != nil {
		return err
	}

	if err := m.writeShellEnv("nu"); err != nil {
		return err
	}
	if err := m.writeShellEnv("sh"); err != nil {
		return err
	}
	if err := m.writeShellEnv("ps1"); err != nil {
		return err
	}

	return nil
}

func (m Meta) writeShellEnv(shell string) error {
	var tmpl string
	switch shell {
	case "nu":
		tmpl = "let-env Path = ($env.Path | append %q)\n"
	case "sh":
		tmpl = "PATH=$PATH:%s\n"
	case "ps1":
		tmpl = `$env:Path = "$env:Path;%s"` + "\n"
	default:
		return errors.New("shell not recognized")
	}
	home, err := os.UserHomeDir()
	if err != nil {
		home = "."
	}
	fp := filepath.Join(home, ".eget", "eget."+shell)
	fi, err := os.Create(fp)
	if err != nil {
		return err
	}
	defer fi.Close()

	var out strings.Builder
	out.WriteString("# managed by eget; DO NOT EDIT\n\n")
	for name := range m.Packages {
		out.WriteString(fmt.Sprintf(tmpl, disk.Path(name)))
	}
	fi.WriteString(out.String())

	return nil
}