// Package archive saves a local copy of each run's fetched data and
// analysis. It doubles as the source of the previous run's report, which
// the prompt uses to dedup successive briefings against each other.
package archive

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

	"gitea.konchin.com/service/stonks/internal/config"
	"gitea.konchin.com/service/stonks/internal/fetch"
	"gitea.konchin.com/service/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, err := resolveDir(cfg)
	if err != nil {
		return "", 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)
	}
	portfolioJSON, err := json.MarshalIndent(run.Report.Portfolio, "", "  ")
	if err != nil {
		return "", fmt.Errorf("archive: marshal portfolio snapshot: %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,
		"portfolio.json":       portfolioJSON,
		"memory.md":            []byte(run.Report.Memory),
	}
	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
}

// RecentRun is one previously-archived run's timestamp and report text, as
// returned by LoadRecent.
type RecentRun struct {
	When   time.Time
	Report string
}

// runDirLayout is the timestamp format run directories are named with (see
// Save), used by LoadRecent to recover each run's time.
const runDirLayout = "20060102T150405Z"

// LoadRecent reads back up to the last n previously-archived runs' report.md
// contents, oldest first, for the prompt to dedup the next briefing against
// a rolling window of recent history. Returns (nil, nil) if no prior run
// exists yet (e.g. first-ever run) — callers should treat that as "no
// previous reports" rather than an error. Runs whose report.md is missing or
// unreadable are skipped rather than failing the whole call.
func LoadRecent(cfg config.ArchiveConfig, n int) ([]RecentRun, error) {
	base, err := resolveDir(cfg)
	if err != nil {
		return nil, err
	}

	entries, err := os.ReadDir(base)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, fmt.Errorf("archive: list %q: %w", base, err)
	}

	var runDirs []string
	for _, e := range entries {
		if e.IsDir() {
			runDirs = append(runDirs, e.Name())
		}
	}
	if len(runDirs) == 0 {
		return nil, nil
	}
	sort.Strings(runDirs) // timestamp-named dirs sort chronologically

	if len(runDirs) > n {
		runDirs = runDirs[len(runDirs)-n:]
	}

	var runs []RecentRun
	for _, name := range runDirs {
		when, err := time.Parse(runDirLayout, name)
		if err != nil {
			continue
		}
		data, err := os.ReadFile(filepath.Join(base, name, "report.md"))
		if err != nil {
			continue
		}
		runs = append(runs, RecentRun{When: when.UTC(), Report: string(data)})
	}
	return runs, nil
}

// resolveDir returns cfg.Dir (or defaultDir if empty) with "~" expanded.
func resolveDir(cfg config.ArchiveConfig) (string, error) {
	base := cfg.Dir
	if base == "" {
		base = defaultDir
	}
	base, err := expandHome(base)
	if err != nil {
		return "", fmt.Errorf("archive: %w", err)
	}
	return base, 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
}