// Copyright (c) 2026 Petr Balvín <opensource@petrbalvin.org> (https://petrbalvin.org)
// SPDX-License-Identifier: MIT

//go:build linux || freebsd

package storage

import (
	"encoding/json"
	"fmt"
	"os"
	"path/filepath"
	"sync"
	"time"
)

// Submission is one archived form submission, one JSON object per line.
// Newsletter forms do not write here: they persist through the double
// opt-in subscriber log instead.
type Submission struct {
	Form      string    `json:"form"`
	Name      string    `json:"name,omitempty"`
	Email     string    `json:"email"`
	Service   string    `json:"service,omitempty"`
	Message   string    `json:"message"`
	IP        string    `json:"ip,omitempty"`
	CreatedAt time.Time `json:"created_at"`
}

// ArchiveStore is a file-based append-only log of submissions. All methods
// are safe for concurrent use. The file and its parent directory are
// created lazily on first Append, so a form that archives nothing writes
// nothing.
type ArchiveStore struct {
	path string
	mu   sync.Mutex
}

// NewArchiveStore returns a store that appends to path.
func NewArchiveStore(path string) *ArchiveStore {
	return &ArchiveStore{path: path}
}

// Path returns the file path this store writes to.
func (s *ArchiveStore) Path() string {
	return s.path
}

// Append writes sub as a single JSON line to the log.
func (s *ArchiveStore) Append(sub Submission) error {
	if sub.CreatedAt.IsZero() {
		sub.CreatedAt = time.Now().UTC()
	}
	line, err := json.Marshal(sub)
	if err != nil {
		return fmt.Errorf("marshal submission: %w", err)
	}
	line = append(line, '\n')

	s.mu.Lock()
	defer s.mu.Unlock()
	return appendLine(s.path, line)
}

// appendLine writes one marshalled JSON line to an append-only log,
// creating the file and its parent directory on first use. The caller
// holds the store's lock.
func appendLine(path string, line []byte) (err error) {
	if err := os.MkdirAll(filepath.Dir(path), 0755); err != nil {
		return fmt.Errorf("mkdir %s: %w", filepath.Dir(path), err)
	}
	f, err := os.OpenFile(path, os.O_APPEND|os.O_CREATE|os.O_WRONLY, 0644)
	if err != nil {
		return fmt.Errorf("open %s: %w", path, err)
	}
	defer func() {
		if cerr := f.Close(); cerr != nil && err == nil {
			err = fmt.Errorf("close %s: %w", path, cerr)
		}
	}()
	if _, err := f.Write(line); err != nil {
		return fmt.Errorf("write %s: %w", path, err)
	}
	return nil
}