package compass

import (
	"fmt"
	"os"
	"path/filepath"
	"strings"

	"github.com/knadh/koanf/parsers/yaml"
	"github.com/knadh/koanf/v2"
)

// Set stores an in-memory override that wins over every file and env layer.
func (c *Config) Set(path string, value any) error {
	if c == nil {
		return fmt.Errorf("compass: config is nil")
	}
	if path == "" {
		return fmt.Errorf("compass: empty config path")
	}
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.runtime == nil {
		c.runtime = koanf.New(".")
	}
	return c.runtime.Set(path, value)
}

// Persist writes runtime overrides to config/env/<env>/overrides.yaml
// using an atomic replace and restrictive file permissions.
func (c *Config) Persist() error {
	if c == nil {
		return fmt.Errorf("compass: config is nil")
	}
	c.mu.Lock()
	defer c.mu.Unlock()
	if c.dir == "" {
		return fmt.Errorf("compass: config directory is empty")
	}
	env, err := sanitizeEnv(c.env)
	if err != nil {
		return err
	}
	destDir, dest, err := overridesPath(c.dir, env)
	if err != nil {
		return err
	}
	if err := os.MkdirAll(destDir, 0o700); err != nil {
		return fmt.Errorf("compass: create overrides dir: %w", err)
	}
	raw := []byte("{}\n")
	if c.runtime != nil {
		body, err := c.runtime.Marshal(yaml.Parser())
		if err != nil {
			return fmt.Errorf("compass: marshal overrides: %w", err)
		}
		raw = body
	}
	tmp := dest + ".tmp"
	if err := os.WriteFile(tmp, raw, 0o600); err != nil {
		return fmt.Errorf("compass: write overrides: %w", err)
	}
	if err := os.Rename(tmp, dest); err != nil {
		_ = os.Remove(tmp)
		return fmt.Errorf("compass: persist overrides: %w", err)
	}
	return nil
}

// Reload rebuilds the tree from disk and plugin sources and clears runtime Set.
func (c *Config) Reload() error {
	if c == nil {
		return fmt.Errorf("compass: config is nil")
	}
	c.mu.Lock()
	defer c.mu.Unlock()
	c.runtime = koanf.New(".")
	if err := c.refreshSources(); err != nil {
		return err
	}
	return c.rebuild()
}

func overridesPath(dir, env string) (destDir, dest string, err error) {
	root, err := filepath.Abs(dir)
	if err != nil {
		return "", "", fmt.Errorf("compass: resolve config dir: %w", err)
	}
	root = filepath.Clean(root)
	destDir = filepath.Clean(filepath.Join(root, "env", env))
	if !within(root, destDir) {
		return "", "", fmt.Errorf("compass: persist path escapes config directory")
	}
	dest = filepath.Clean(filepath.Join(destDir, "overrides.yaml"))
	if !within(destDir, dest) {
		return "", "", fmt.Errorf("compass: persist path escapes config directory")
	}
	return destDir, dest, nil
}

func within(root, path string) bool {
	rel, err := filepath.Rel(root, path)
	if err != nil {
		return false
	}
	return rel == "." || (rel != ".." && !strings.HasPrefix(rel, ".."+string(os.PathSeparator)))
}