/*
History — Persistent deployment history for Volt.

Stores deployment records as YAML in /var/lib/volt/deployments/.
Each target gets its own history file to keep lookups fast.

Copyright (c) Armored Gates LLC. All rights reserved.
*/
package deploy

import (
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strings"
	"sync"
	"time"

	"gopkg.in/yaml.v3"
)

// ── Constants ────────────────────────────────────────────────────────────────

const (
	// DefaultHistoryDir is where deployment history files are stored.
	DefaultHistoryDir = "/var/lib/volt/deployments"
)

// ── History Entry ────────────────────────────────────────────────────────────

// HistoryEntry records a single deployment operation.
type HistoryEntry struct {
	ID               string    `yaml:"id" json:"id"`
	Target           string    `yaml:"target" json:"target"`
	Strategy         string    `yaml:"strategy" json:"strategy"`
	OldRef           string    `yaml:"old_ref" json:"old_ref"`
	NewRef           string    `yaml:"new_ref" json:"new_ref"`
	Status           string    `yaml:"status" json:"status"` // "complete", "failed", "rolling-back"
	StartedAt        time.Time `yaml:"started_at" json:"started_at"`
	CompletedAt      time.Time `yaml:"completed_at" json:"completed_at"`
	InstancesUpdated int       `yaml:"instances_updated" json:"instances_updated"`
	Message          string    `yaml:"message,omitempty" json:"message,omitempty"`
}

// ── History Store ────────────────────────────────────────────────────────────

// HistoryStore manages deployment history on disk.
type HistoryStore struct {
	dir string
	mu  sync.Mutex
}

// NewHistoryStore creates a history store at the given directory.
func NewHistoryStore(dir string) *HistoryStore {
	if dir == "" {
		dir = DefaultHistoryDir
	}
	return &HistoryStore{dir: dir}
}

// Dir returns the history directory path.
func (h *HistoryStore) Dir() string {
	return h.dir
}

// historyFile returns the path to the history file for a target.
func (h *HistoryStore) historyFile(target string) string {
	// Sanitize the target name for use as a filename.
	safe := strings.Map(func(r rune) rune {
		if (r >= 'a' && r <= 'z') || (r >= 'A' && r <= 'Z') ||
			(r >= '0' && r <= '9') || r == '-' || r == '_' {
			return r
		}
		return '_'
	}, target)
	return filepath.Join(h.dir, safe+".yaml")
}

// Append adds a deployment entry to the target's history file.
func (h *HistoryStore) Append(entry HistoryEntry) error {
	h.mu.Lock()
	defer h.mu.Unlock()

	if err := os.MkdirAll(h.dir, 0755); err != nil {
		return fmt.Errorf("history: create dir: %w", err)
	}

	// Load existing entries.
	entries, _ := h.readEntries(entry.Target) // ignore error on first write

	// Append and write.
	entries = append(entries, entry)

	return h.writeEntries(entry.Target, entries)
}

// ListByTarget returns all deployment history for a target, most recent first.
func (h *HistoryStore) ListByTarget(target string) ([]HistoryEntry, error) {
	h.mu.Lock()
	defer h.mu.Unlock()

	entries, err := h.readEntries(target)
	if err != nil {
		return nil, err
	}

	// Sort by StartedAt descending (most recent first).
	sort.Slice(entries, func(i, j int) bool {
		return entries[i].StartedAt.After(entries[j].StartedAt)
	})

	return entries, nil
}

// ListAll returns all deployment history across all targets, most recent first.
func (h *HistoryStore) ListAll() ([]HistoryEntry, error) {
	h.mu.Lock()
	defer h.mu.Unlock()

	files, err := filepath.Glob(filepath.Join(h.dir, "*.yaml"))
	if err != nil {
		return nil, fmt.Errorf("history: glob: %w", err)
	}

	var all []HistoryEntry
	for _, f := range files {
		data, err := os.ReadFile(f)
		if err != nil {
			continue
		}
		var entries []HistoryEntry
		if err := yaml.Unmarshal(data, &entries); err != nil {
			continue
		}
		all = append(all, entries...)
	}

	sort.Slice(all, func(i, j int) bool {
		return all[i].StartedAt.After(all[j].StartedAt)
	})

	return all, nil
}

// readEntries loads entries from the history file for a target.
// Returns empty slice (not error) if file doesn't exist.
func (h *HistoryStore) readEntries(target string) ([]HistoryEntry, error) {
	filePath := h.historyFile(target)
	data, err := os.ReadFile(filePath)
	if err != nil {
		if os.IsNotExist(err) {
			return nil, nil
		}
		return nil, fmt.Errorf("history: read %s: %w", filePath, err)
	}

	var entries []HistoryEntry
	if err := yaml.Unmarshal(data, &entries); err != nil {
		return nil, fmt.Errorf("history: parse %s: %w", filePath, err)
	}

	return entries, nil
}

// writeEntries writes entries to the history file for a target.
func (h *HistoryStore) writeEntries(target string, entries []HistoryEntry) error {
	filePath := h.historyFile(target)

	data, err := yaml.Marshal(entries)
	if err != nil {
		return fmt.Errorf("history: marshal: %w", err)
	}

	// Atomic write: tmp + rename.
	tmpPath := filePath + ".tmp"
	if err := os.WriteFile(tmpPath, data, 0644); err != nil {
		return fmt.Errorf("history: write %s: %w", tmpPath, err)
	}
	if err := os.Rename(tmpPath, filePath); err != nil {
		os.Remove(tmpPath)
		return fmt.Errorf("history: rename %s: %w", filePath, err)
	}

	return nil
}