package pkg

import (
	"encoding/json"
	"fmt"
	"io"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
)

// Manifest is the agent-native.json discovered in a package.
type Manifest struct {
	Name       string            `json:"name"`
	Extensions []string          `json:"extensions,omitempty"`
	Config     map[string]string `json:"config,omitempty"`
}

// Manager installs packages under Dir.
type Manager struct {
	Dir string
}

func (m Manager) root() string {
	if m.Dir != "" {
		return m.Dir
	}
	home, _ := os.UserHomeDir()
	return filepath.Join(home, ".agent-native", "packages")
}

// Install copies a local directory, clones a git URL, or runs npm pack
// when src starts with "npm:". The package name comes from its manifest.
func (m Manager) Install(src string) (Manifest, error) {
	dir, err := os.MkdirTemp("", "agent-native-pkg-*")
	if err != nil {
		return Manifest{}, err
	}
	defer os.RemoveAll(dir)
	switch {
	case strings.HasPrefix(src, "npm:"):
		if _, err := exec.LookPath("npm"); err != nil {
			return Manifest{}, fmt.Errorf("pkg: npm is not installed")
		}
		cmd := exec.Command("npm", "pack", strings.TrimPrefix(src, "npm:"))
		cmd.Dir = dir
		if out, err := cmd.CombinedOutput(); err != nil {
			return Manifest{}, fmt.Errorf("pkg: npm pack: %s", out)
		}
	case strings.HasPrefix(src, "git+") || strings.HasSuffix(src, ".git") || strings.Contains(src, "://"):
		cmd := exec.Command("git", "clone", "--depth", "1", src, filepath.Join(dir, "src"))
		if out, err := cmd.CombinedOutput(); err != nil {
			return Manifest{}, fmt.Errorf("pkg: git clone: %s", out)
		}
		dir = filepath.Join(dir, "src")
	default:
		if err := copyDir(src, filepath.Join(dir, "src")); err != nil {
			return Manifest{}, err
		}
		dir = filepath.Join(dir, "src")
	}
	manifest, err := ReadManifest(dir)
	if err != nil {
		return Manifest{}, err
	}
	dest := filepath.Join(m.root(), manifest.Name)
	if err := os.RemoveAll(dest); err != nil {
		return Manifest{}, err
	}
	if err := copyDir(dir, dest); err != nil {
		return Manifest{}, err
	}
	return manifest, nil
}

// Remove deletes an installed package.
func (m Manager) Remove(name string) error {
	return os.RemoveAll(filepath.Join(m.root(), name))
}

// Update reinstalls from the recorded source when present, otherwise no-ops.
func (m Manager) Update(name string) (Manifest, error) {
	manifest, err := ReadManifest(filepath.Join(m.root(), name))
	if err != nil {
		return Manifest{}, err
	}
	src := manifest.Config["source"]
	if src == "" {
		return manifest, nil
	}
	return m.Install(src)
}

// List returns installed manifests.
func (m Manager) List() ([]Manifest, error) {
	entries, err := os.ReadDir(m.root())
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, err
	}
	var out []Manifest
	for _, ent := range entries {
		if !ent.IsDir() {
			continue
		}
		manifest, err := ReadManifest(filepath.Join(m.root(), ent.Name()))
		if err != nil {
			continue
		}
		out = append(out, manifest)
	}
	return out, nil
}

// Config sets one package config key.
func (m Manager) Config(name, key, value string) error {
	path := filepath.Join(m.root(), name)
	manifest, err := ReadManifest(path)
	if err != nil {
		return err
	}
	if manifest.Config == nil {
		manifest.Config = map[string]string{}
	}
	manifest.Config[key] = value
	raw, err := json.MarshalIndent(manifest, "", "  ")
	if err != nil {
		return err
	}
	return os.WriteFile(filepath.Join(path, "agent-native.json"), raw, 0o644)
}

// ReadManifest loads agent-native.json from a directory.
func ReadManifest(dir string) (Manifest, error) {
	raw, err := os.ReadFile(filepath.Join(dir, "agent-native.json"))
	if err != nil {
		return Manifest{}, err
	}
	var manifest Manifest
	if err := json.Unmarshal(raw, &manifest); err != nil {
		return Manifest{}, err
	}
	if manifest.Name == "" {
		return Manifest{}, fmt.Errorf("pkg: manifest name is empty")
	}
	return manifest, nil
}

func copyDir(src, dst string) error {
	return filepath.Walk(src, func(path string, info os.FileInfo, err error) error {
		if err != nil {
			return err
		}
		rel, err := filepath.Rel(src, path)
		if err != nil {
			return err
		}
		target := filepath.Join(dst, rel)
		if info.IsDir() {
			return os.MkdirAll(target, 0o755)
		}
		if err := os.MkdirAll(filepath.Dir(target), 0o755); err != nil {
			return err
		}
		in, err := os.Open(path)
		if err != nil {
			return err
		}
		defer in.Close()
		out, err := os.OpenFile(target, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, info.Mode())
		if err != nil {
			return err
		}
		defer out.Close()
		_, err = io.Copy(out, in)
		return err
	})
}