// Package memory persists Claude's own freeform notes between runs — its
// running thesis on positions, why past calls were made, and anything else
// it wants available as context for future decisions. It is intentionally
// just a flat text file: Claude rewrites it each run (Load hands back the
// previous content, Save overwrites with the new content extracted from the
// response), so summarization and pruning are Claude's job, not Go's.
package memory

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

	"gitea.konchin.com/service/stonks/internal/config"
)

const fileName = "memory.md"

// Load reads back the memory file from cfg.Dir. Returns "" with no error if
// it doesn't exist yet (e.g. first-ever run).
func Load(cfg config.PortfolioConfig) (string, error) {
	dir, err := resolveDir(cfg.Dir)
	if err != nil {
		return "", err
	}

	data, err := os.ReadFile(filepath.Join(dir, fileName))
	if err != nil {
		if os.IsNotExist(err) {
			return "", nil
		}
		return "", fmt.Errorf("memory: read: %w", err)
	}
	return string(data), nil
}

// Save overwrites the memory file under cfg.Dir with content. A blank
// content is a no-op — it leaves whatever was there alone, rather than
// wiping out prior notes if Claude's response happened to omit the section.
func Save(cfg config.PortfolioConfig, content string) error {
	content = strings.TrimSpace(content)
	if content == "" {
		return nil
	}

	dir, err := resolveDir(cfg.Dir)
	if err != nil {
		return err
	}
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return fmt.Errorf("memory: create %q: %w", dir, err)
	}
	if err := os.WriteFile(filepath.Join(dir, fileName), []byte(content+"\n"), 0o644); err != nil {
		return fmt.Errorf("memory: write: %w", err)
	}
	return nil
}

func resolveDir(dir string) (string, error) {
	if dir == "" {
		dir = "~/.local/state/stonks"
	}
	if dir != "~" && !strings.HasPrefix(dir, "~/") {
		return dir, nil
	}
	home, err := os.UserHomeDir()
	if err != nil {
		return "", fmt.Errorf("memory: resolve home directory: %w", err)
	}
	if dir == "~" {
		return home, nil
	}
	return filepath.Join(home, dir[2:]), nil
}