package agent

import (
	"os"
	"path/filepath"
)

// Cache persists the last known-good rendered config to disk so the agent can
// keep applying it when the control plane is unreachable (never fail closed).
type Cache struct {
	Path string
}

// Write atomically stores the raw config bytes.
func (c Cache) Write(raw []byte) error {
	if err := os.MkdirAll(filepath.Dir(c.Path), 0o755); err != nil {
		return err
	}
	tmp := c.Path + ".tmp"
	if err := os.WriteFile(tmp, raw, 0o600); err != nil {
		return err
	}
	return os.Rename(tmp, c.Path)
}

// Read returns the cached config, or (nil, nil) when no cache exists yet.
func (c Cache) Read() (*RenderedConfig, error) {
	raw, err := os.ReadFile(c.Path)
	if os.IsNotExist(err) {
		return nil, nil
	}
	if err != nil {
		return nil, err
	}
	return ParseRendered(raw)
}