feat: Initial support for Compose configs (#116)

pkg/api/config.go

@@ -0,0 +1,125 @@
+// Implementation of Config feature from the Compose spec
+package api
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strconv"
+)
+
+// ConfigSpec defines a configuration object that can be mounted into containers
+type ConfigSpec struct {
+	Name string
+
+	// Content of the config when specified inline
+	Content []byte `json:",omitempty"`
+
+	// Note: NOT IMPLEMENTED
+	// External indicates this config already exists and should not be created
+	// External bool `json:",omitempty"`
+
+	// Note: NOT IMPLEMENTED
+	// Labels for the config
+	// Labels map[string]string `json:",omitempty"`
+
+	// TODO: add support for "environment"
+}
+
+func (c *ConfigSpec) Validate() error {
+	if c.Name == "" {
+		return fmt.Errorf("config name is required")
+	}
+	return nil
+}
+
+// Equals compares two ConfigSpec instances
+func (c *ConfigSpec) Equals(other ConfigSpec) bool {
+	return c.Name == other.Name &&
+		bytes.Equal(c.Content, other.Content)
+}
+
+// ConfigMount defines how a config is mounted into a container
+type ConfigMount struct {
+	// ConfigName references a config defined in ServiceSpec.Configs by its Name field
+	ConfigName string
+	// ContainerPath is the absolute path where the config is mounted in the container
+	ContainerPath string `json:",omitempty"`
+	// Uid for the mounted config file
+	Uid string `json:",omitempty"`
+	// Gid for the mounted config file
+	Gid string `json:",omitempty"`
+	// Mode (file permissions) for the mounted config file
+	Mode *os.FileMode `json:",omitempty"`
+}
+
+func (c *ConfigMount) GetNumericUid() (*uint64, error) {
+	if c.Uid == "" {
+		return nil, nil
+	}
+	uid, err := strconv.ParseUint(c.Uid, 10, 64)
+	if err != nil {
+		return nil, fmt.Errorf("invalid Uid '%s': %w", c.Uid, err)
+	}
+	if int(uid) < 0 {
+		return nil, fmt.Errorf("invalid Uid '%s': value too high", c.Uid)
+	}
+	return &uid, nil
+}
+
+func (c *ConfigMount) GetNumericGid() (*uint64, error) {
+	if c.Gid == "" {
+		return nil, nil
+	}
+	gid, err := strconv.ParseUint(c.Gid, 10, 64)
+	if err != nil {
+		return nil, fmt.Errorf("invalid Gid '%s': %w", c.Gid, err)
+	}
+	if int(gid) < 0 {
+		return nil, fmt.Errorf("invalid Gid '%s': value too high", c.Gid)
+	}
+	return &gid, nil
+}
+
+func (c *ConfigMount) Validate() error {
+	if c.ConfigName == "" {
+		return fmt.Errorf("config mount source is required")
+	}
+	if _, err := c.GetNumericUid(); err != nil {
+		return err
+	}
+	if _, err := c.GetNumericGid(); err != nil {
+		return err
+	}
+	if c.ContainerPath != "" && !filepath.IsAbs(c.ContainerPath) {
+		return fmt.Errorf("container path must be absolute")
+	}
+	return nil
+}
+
+// ValidateConfigsAndMounts takes config specs and config mounts and validates that all mounts refer to existing specs
+func ValidateConfigsAndMounts(configs []ConfigSpec, mounts []ConfigMount) error {
+	configMap := make(map[string]struct{})
+	for _, cfg := range configs {
+		if err := cfg.Validate(); err != nil {
+			return fmt.Errorf("invalid config: %w", err)
+		}
+		if _, ok := configMap[cfg.Name]; ok {
+			return fmt.Errorf("duplicate config name: '%s'", cfg.Name)
+		}
+
+		configMap[cfg.Name] = struct{}{}
+	}
+
+	for _, mount := range mounts {
+		if err := mount.Validate(); err != nil {
+			return fmt.Errorf("invalid config mount: %w", err)
+		}
+		if _, exists := configMap[mount.ConfigName]; !exists {
+			return fmt.Errorf("config mount source '%s' does not refer to any defined config", mount.ConfigName)
+		}
+	}
+
+	return nil
+}