package lua

import (
	"encoding/json"
	"os"
	"sort"
)

// Access overrides are OPERATOR policy, not plugin data. They live in their own
// file rather than in each plugin's state because:
//
//   - they describe the deployment, not the plugin, so a plugin upgrade that
//     replaces its .state.json must not silently widen access again;
//   - they must survive a restart. An in-memory map made "restrict billing to
//     admin" look like it worked right up to the next deploy, at which point the
//     restriction evaporated with nothing in the logs to say why;
//   - the plugin_dir is the one place an operator already looks when asking
//     "what does this plugin actually get to see", so the answer lives beside it.
//
// The file is a flat map of "name" (whole plugin) or "name#path" (one endpoint)
// to an access spec, which is the same shape the in-memory store uses, so load
// and save cannot disagree about what a key means.

const accessFileName = ".access.json"

func (ps *Plugins) accessFile() string {
	if ps.dir == "" {
		return ""
	}
	return ps.dir + string(os.PathSeparator) + accessFileName
}

// LoadAccessOverrides reads the persisted overrides into memory. A missing file
// is not an error: no operator has restricted anything yet, which is the
// default state of a fresh install.
//
// A corrupt file is also not fatal. Losing a restriction is bad, but refusing to
// start the gateway is worse, and an empty map plus a logged error leaves the
// operator with something to fix.
func (ps *Plugins) LoadAccessOverrides() error {
	path := ps.accessFile()
	if path == "" {
		return nil
	}
	b, err := os.ReadFile(path)
	if os.IsNotExist(err) {
		return nil
	}
	if err != nil {
		return err
	}
	m := map[string]string{}
	if err := json.Unmarshal(b, &m); err != nil {
		return err
	}
	ps.mu.Lock()
	defer ps.mu.Unlock()
	if ps.visibility == nil {
		ps.visibility = visibilityOverrides{}
	}
	for k, v := range m {
		ps.visibility[k] = v
	}
	return nil
}

// saveAccessOverridesLocked flushes the whole override map. It is called on
// every change, and unlike plugin state the map is tiny and changes only when an
// operator clicks Save — so a synchronous write costs nothing that matters, and
// it means the change is durable the moment the API returns 200.
func (ps *Plugins) saveAccessOverridesLocked() {
	path := ps.accessFile()
	if path == "" {
		return
	}
	out := make(map[string]string, len(ps.visibility))
	for k, v := range ps.visibility {
		if v != "" {
			out[k] = v
		}
	}
	if len(out) == 0 {
		// Leave no empty file behind: its absence is the honest encoding of
		// "nothing is overridden".
		_ = os.Remove(path)
		return
	}
	writeJSONAtomic(path, out)
}

// AccessOverrides returns a copy of every override in force, for the UI.
func (ps *Plugins) accessOverridesSnapshot() map[string]string {
	ps.mu.RLock()
	defer ps.mu.RUnlock()
	if len(ps.visibility) == 0 {
		return nil
	}
	out := make(map[string]string, len(ps.visibility))
	for k, v := range ps.visibility {
		out[k] = v
	}
	return out
}

// sortedOverrideKeys exists only so a debug dump is stable; map iteration order
// would otherwise make two identical states look different.
func (ps *Plugins) sortedOverrideKeys() []string {
	m := ps.accessOverridesSnapshot()
	keys := make([]string, 0, len(m))
	for k := range m {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	return keys
}