// Package changelog manages the infrastructure changelog log.
package changelog

import (
	"encoding/json"
	"fmt"
	"os"
	"sort"
	"time"
)

// Categories available for changelog entries.
var Categories = []string{"hardware", "network", "software", "migration"}

// Entry is a single changelog entry.
type Entry struct {
	ID          string `json:"id"`
	Date        string `json:"date"`        // YYYY-MM-DD
	Title       string `json:"title"`
	Description string `json:"description"`
	Category    string `json:"category"` // hardware, network, software, migration
}

// Log holds all changelog entries.
type Log struct {
	Entries []Entry `json:"entries"`
}

// Load reads the changelog from path. Returns an empty log if the file does not exist.
func Load(path string) (*Log, error) {
	raw, err := os.ReadFile(path)
	if err != nil {
		if os.IsNotExist(err) {
			return &Log{}, nil
		}
		return nil, err
	}
	var l Log
	if err := json.Unmarshal(raw, &l); err != nil {
		return nil, err
	}
	sort.Slice(l.Entries, func(i, j int) bool {
		return l.Entries[i].Date > l.Entries[j].Date
	})
	return &l, nil
}

// save writes the log to path without sorting (internal use).
func save(path string, l *Log) error {
	raw, err := json.MarshalIndent(l, "", "  ")
	if err != nil {
		return err
	}
	return os.WriteFile(path, raw, 0644)
}

// Add appends a new entry and saves.
func Add(path string, e Entry) error {
	l, err := Load(path)
	if err != nil {
		return err
	}
	e.ID = fmt.Sprintf("%d", time.Now().UnixNano())
	l.Entries = append(l.Entries, e)
	return save(path, l)
}

// Update replaces an entry by ID and saves.
func Update(path string, e Entry) error {
	l, err := Load(path)
	if err != nil {
		return err
	}
	for i, entry := range l.Entries {
		if entry.ID == e.ID {
			l.Entries[i] = e
			return save(path, l)
		}
	}
	return fmt.Errorf("entry %s not found", e.ID)
}

// Delete removes an entry by ID and saves.
func Delete(path string, id string) error {
	l, err := Load(path)
	if err != nil {
		return err
	}
	kept := l.Entries[:0]
	for _, e := range l.Entries {
		if e.ID != id {
			kept = append(kept, e)
		}
	}
	l.Entries = kept
	return save(path, l)
}

// Get returns a single entry by ID.
func Get(path string, id string) (*Entry, error) {
	l, err := Load(path)
	if err != nil {
		return nil, err
	}
	for _, e := range l.Entries {
		if e.ID == id {
			return &e, nil
		}
	}
	return nil, fmt.Errorf("entry %s not found", id)
}