1 files changed, 105 insertions, 0 deletions

diff --git a/internal/detect/detect.go b/internal/detect/detect.go
new file mode 100644
index 0000000..f3efd22
--- /dev/null
+++ b/internal/detect/detect.go
@@ -0,0 +1,105 @@
+// Package detect provides auto-detection of project types.
+package detect
+
+import (
+        "os"
+        "path/filepath"
+
+        "github.com/bdw/ship/internal/output"
+)
+
+// ProjectType represents the detected deployment type
+type ProjectType string
+
+const (
+        TypeStatic ProjectType = "static"
+        TypeDocker ProjectType = "docker"
+        TypeBinary ProjectType = "binary"
+)
+
+// Result is the detection outcome
+type Result struct {
+        Type    ProjectType
+        Path    string // Absolute path to deploy
+        Error   *output.ErrorResponse
+}
+
+// Detect examines a path and determines how to deploy it.
+// Follows the logic from SPEC.md:
+//   - File: must be executable → binary
+//   - Directory with Dockerfile → docker
+//   - Directory with index.html → static
+//   - Go/Node without Dockerfile → error with guidance
+//   - Empty or unknown → error
+func Detect(path string) Result {
+        absPath, err := filepath.Abs(path)
+        if err != nil {
+                return Result{Error: output.Err(output.ErrInvalidPath, "cannot resolve path: "+err.Error())}
+        }
+
+        info, err := os.Stat(absPath)
+        if err != nil {
+                if os.IsNotExist(err) {
+                        return Result{Error: output.Err(output.ErrInvalidPath, "path does not exist: "+path)}
+                }
+                return Result{Error: output.Err(output.ErrInvalidPath, "cannot access path: "+err.Error())}
+        }
+
+        // File: must be executable binary
+        if !info.IsDir() {
+                return detectFile(absPath, info)
+        }
+
+        // Directory: check contents
+        return detectDirectory(absPath)
+}
+
+func detectFile(path string, info os.FileInfo) Result {
+        // Check if executable
+        if info.Mode()&0111 == 0 {
+                return Result{Error: output.Err(output.ErrUnknownProjectType, "file is not executable")}
+        }
+        return Result{Type: TypeBinary, Path: path}
+}
+
+func detectDirectory(path string) Result {
+        // Check for Dockerfile first (highest priority)
+        if hasFile(path, "Dockerfile") {
+                return Result{Type: TypeDocker, Path: path}
+        }
+
+        // Check for static site
+        if hasFile(path, "index.html") || hasFile(path, "index.htm") {
+                return Result{Type: TypeStatic, Path: path}
+        }
+
+        // Check for Go project without Dockerfile
+        if hasFile(path, "go.mod") {
+                return Result{Error: output.Err(output.ErrUnknownProjectType,
+                        "Go project without Dockerfile. Add a Dockerfile or build a binary first.")}
+        }
+
+        // Check for Node project without Dockerfile
+        if hasFile(path, "package.json") {
+                return Result{Error: output.Err(output.ErrUnknownProjectType,
+                        "Node project without Dockerfile. Add a Dockerfile.")}
+        }
+
+        // Check if empty
+        entries, err := os.ReadDir(path)
+        if err != nil {
+                return Result{Error: output.Err(output.ErrInvalidPath, "cannot read directory: "+err.Error())}
+        }
+        if len(entries) == 0 {
+                return Result{Error: output.Err(output.ErrInvalidPath, "directory is empty")}
+        }
+
+        // Unknown
+        return Result{Error: output.Err(output.ErrUnknownProjectType,
+                "cannot detect project type. Add a Dockerfile or index.html.")}
+}
+
+func hasFile(dir, name string) bool {
+        _, err := os.Stat(filepath.Join(dir, name))
+        return err == nil
+}