package vcs

import (
	"fmt"

	"github.com/go-git/go-git/v5/plumbing"
	"tangled.org/core/knotserver/git"
	"tangled.org/core/knotserver/pijul"
)

// Open opens a repository at path with the given ref (branch/tag/hash).
// It auto-detects the VCS type and returns the appropriate adapter.
// For git, ref is resolved as a revision; for pijul, ref is the channel name.
func Open(path, ref string) (ReadRepo, error) {
	vcsType, err := DetectVCS(path)
	if err != nil {
		return nil, err
	}

	switch vcsType {
	case "git":
		g, err := git.Open(path, ref)
		if err != nil {
			return nil, err
		}
		return newGitReadAdapter(g), nil
	case "pijul":
		p, err := pijul.Open(path, ref)
		if err != nil {
			return nil, err
		}
		return newPijulReadAdapter(p), nil
	default:
		return nil, fmt.Errorf("unsupported VCS type: %s", vcsType)
	}
}

// PlainOpen opens a repository at path without setting a specific ref.
// Returns a MutableRepo since no ref is pinned.
func PlainOpen(path string) (MutableRepo, error) {
	vcsType, err := DetectVCS(path)
	if err != nil {
		return nil, err
	}

	switch vcsType {
	case "git":
		g, err := git.PlainOpen(path)
		if err != nil {
			return nil, err
		}
		return newGitMutableAdapter(g), nil
	case "pijul":
		p, err := pijul.PlainOpen(path)
		if err != nil {
			return nil, err
		}
		return newPijulMutableAdapter(p), nil
	default:
		return nil, fmt.Errorf("unsupported VCS type: %s", vcsType)
	}
}

// AsGit returns the underlying *git.GitRepo if repo is a git adapter, or nil.
// Use this for git-specific operations that don't belong in the VCS interface.
func AsGit(repo ReadRepo) *git.GitRepo {
	switch r := repo.(type) {
	case *gitReadAdapter:
		return r.Git()
	case *gitMutableAdapter:
		return r.Git()
	}
	return nil
}

// AsPijul returns the underlying *pijul.PijulRepo if repo is a pijul adapter, or nil.
// Use this for pijul-specific operations that don't belong in the VCS interface.
func AsPijul(repo ReadRepo) *pijul.PijulRepo {
	switch r := repo.(type) {
	case *pijulReadAdapter:
		return r.Pijul()
	case *pijulMutableAdapter:
		return r.Pijul()
	}
	return nil
}

// gitHash converts a hex string to a plumbing.Hash.
func gitHash(s string) plumbing.Hash {
	return plumbing.NewHash(s)
}