// Package archive optionally saves a local copy of each run's fetched data
// and analysis, for debugging prompt/parsing issues without reproducing a
// live run.
package archive

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"strings"
	"time"

	"github.com/ytshih/stonks/internal/config"
	"github.com/ytshih/stonks/internal/fetch"
	"github.com/ytshih/stonks/internal/report"
)

const defaultDir = "~/.local/state/stonks/runs"

// Run holds everything one pipeline run produced, for archiving.
type Run struct {
	Result      fetch.Result
	Prompt      string // final prompt sent to the analyzer, including any advisor section
	RawResponse string // analyzer's raw, unparsed response
	Report      report.Report
}

// Save writes Run's artifacts to a new timestamped subdirectory under
// cfg.Dir (or defaultDir if cfg.Dir is empty) and returns that directory's
// path. Callers should treat a non-nil error as non-fatal — archiving is a
// debugging aid, not part of the report pipeline.
func Save(cfg config.ArchiveConfig, run Run, now time.Time) (string, error) {
	base := cfg.Dir
	if base == "" {
		base = defaultDir
	}
	base, err := expandHome(base)
	if err != nil {
		return "", fmt.Errorf("archive: %w", err)
	}

	dir := filepath.Join(base, now.UTC().Format("20060102T150405Z"))
	if err := os.MkdirAll(dir, 0o755); err != nil {
		return "", fmt.Errorf("archive: create %q: %w", dir, err)
	}

	fetchedJSON, err := json.MarshalIndent(run.Result, "", "  ")
	if err != nil {
		return "", fmt.Errorf("archive: marshal fetched data: %w", err)
	}
	recsJSON, err := json.MarshalIndent(run.Report.Recommendations, "", "  ")
	if err != nil {
		return "", fmt.Errorf("archive: marshal recommendations: %w", err)
	}

	files := map[string][]byte{
		"fetched.json":         fetchedJSON,
		"prompt.txt":           []byte(run.Prompt),
		"analysis_raw.md":      []byte(run.RawResponse),
		"report.md":            []byte(run.Report.Text),
		"recommendations.json": recsJSON,
	}
	for name, data := range files {
		if err := os.WriteFile(filepath.Join(dir, name), data, 0o644); err != nil {
			return dir, fmt.Errorf("archive: write %q: %w", name, err)
		}
	}

	return dir, nil
}

// expandHome replaces a leading "~" with the current user's home directory.
func expandHome(path string) (string, error) {
	if path != "~" && !strings.HasPrefix(path, "~/") {
		return path, nil
	}
	home, err := os.UserHomeDir()
	if err != nil {
		return "", fmt.Errorf("resolve home directory: %w", err)
	}
	if path == "~" {
		return home, nil
	}
	return filepath.Join(home, path[2:]), nil
}