// Package git is a thin wrapper around the git binary. It runs porcelain
// commands via os/exec with a per-command timeout so a scan can never hang
// on a broken or unresponsive repository.
package git

import (
	"bytes"
	"context"
	"fmt"
	"os"
	"os/exec"
	"strings"
	"time"
)

// DefaultTimeout bounds every git invocation. A single hung git call would
// otherwise stall the whole scan.
const DefaultTimeout = 10 * time.Second

// Executor runs git commands against a repository working directory.
type Executor struct {
	bin     string
	timeout time.Duration
	env     []string
}

// Option configures an Executor (functional options pattern).
type Option func(*Executor)

// WithBinary overrides the git executable path (default "git").
func WithBinary(bin string) Option {
	return func(e *Executor) { e.bin = bin }
}

// WithTimeout overrides the per-command timeout (default 10s).
func WithTimeout(d time.Duration) Option {
	return func(e *Executor) { e.timeout = d }
}

// WithEnv appends extra environment variables to every command.
func WithEnv(env ...string) Option {
	return func(e *Executor) { e.env = append(e.env, env...) }
}

// NewExecutor builds an Executor with sensible defaults.
func NewExecutor(opts ...Option) *Executor {
	e := &Executor{bin: "git", timeout: DefaultTimeout}
	for _, opt := range opts {
		opt(e)
	}
	return e
}

// Run executes git <args...> in dir with a context timeout and returns the
// trimmed stdout. Context cancellation is honoured; the configured timeout
// guards against a hanging repository.
func (e *Executor) Run(ctx context.Context, dir string, args ...string) (string, error) {
	ctx, cancel := context.WithTimeout(ctx, e.timeout)
	defer cancel()

	cmd := exec.CommandContext(ctx, e.bin, args...)
	cmd.Dir = dir
	cmd.Env = append(os.Environ(), e.env...)

	var stdout, stderr bytes.Buffer
	cmd.Stdout = &stdout
	cmd.Stderr = &stderr

	if err := cmd.Run(); err != nil {
		if ctx.Err() != nil {
			return "", fmt.Errorf("git %s: timed out after %s", strings.Join(args, " "), e.timeout)
		}
		msg := strings.TrimSpace(stderr.String())
		if msg == "" {
			msg = err.Error()
		}
		return "", fmt.Errorf("git %s: %s", strings.Join(args, " "), msg)
	}
	return strings.TrimSpace(stdout.String()), nil
}