package cli

import (
	"encoding/json"
	"fmt"
	"net/http"
	"os"
	"os/exec"
	"path/filepath"
	"strings"
	"time"
)

// GitHubRelease is the subset of the GitHub releases API response we need.
type GitHubRelease struct {
	TagName string `json:"tag_name"`
	HTMLURL string `json:"html_url"`
}

// FetchLatestRelease fetches the latest release tag from the multica GitHub repo.
func FetchLatestRelease() (*GitHubRelease, error) {
	client := &http.Client{Timeout: 10 * time.Second}
	req, err := http.NewRequest(http.MethodGet, "https://api.github.com/repos/multica-ai/multica/releases/latest", nil)
	if err != nil {
		return nil, err
	}
	req.Header.Set("Accept", "application/vnd.github+json")

	resp, err := client.Do(req)
	if err != nil {
		return nil, err
	}
	defer resp.Body.Close()

	if resp.StatusCode != http.StatusOK {
		return nil, fmt.Errorf("GitHub API returned %d", resp.StatusCode)
	}

	var release GitHubRelease
	if err := json.NewDecoder(resp.Body).Decode(&release); err != nil {
		return nil, err
	}
	return &release, nil
}

// IsBrewInstall checks whether the running multica binary was installed via Homebrew.
func IsBrewInstall() bool {
	exePath, err := os.Executable()
	if err != nil {
		return false
	}
	resolved, err := filepath.EvalSymlinks(exePath)
	if err != nil {
		resolved = exePath
	}

	brewPrefix := GetBrewPrefix()
	if brewPrefix != "" && strings.HasPrefix(resolved, brewPrefix) {
		return true
	}

	for _, prefix := range []string{"/opt/homebrew", "/usr/local", "/home/linuxbrew/.linuxbrew"} {
		if strings.HasPrefix(resolved, prefix+"/Cellar/") {
			return true
		}
	}
	return false
}

// GetBrewPrefix returns the Homebrew prefix by running `brew --prefix`, or empty string.
func GetBrewPrefix() string {
	out, err := exec.Command("brew", "--prefix").Output()
	if err != nil {
		return ""
	}
	return strings.TrimSpace(string(out))
}

// UpdateViaBrew runs `brew upgrade multica-ai/tap/multica`.
// Returns the combined output and any error.
func UpdateViaBrew() (string, error) {
	cmd := exec.Command("brew", "upgrade", "multica-ai/tap/multica")
	out, err := cmd.CombinedOutput()
	if err != nil {
		return string(out), fmt.Errorf("brew upgrade failed: %w", err)
	}
	return string(out), nil
}

// DetectNewBinaryPath returns the path to the multica binary after an update.
// It uses exec.LookPath to find the binary in PATH, which will resolve to the
// updated version after a brew upgrade.
func DetectNewBinaryPath() (string, error) {
	return exec.LookPath("multica")
}