package history

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

const (
	histRelPath = "_history/format-history.json"
	maxEntries  = 20
)

type HistoryEntry struct {
	Slug    string `json:"slug"`
	Formato string `json:"formato"`
	Data    string `json:"data"` // YYYY-MM-DD
}

type FormatHistory struct {
	History []HistoryEntry `json:"history"`
}

// LoadHistory reads _history/format-history.json from workspacePath.
// Returns empty history if file doesn't exist.
func LoadHistory(workspacePath string) (*FormatHistory, error) {
	path := filepath.Join(workspacePath, histRelPath)
	data, err := os.ReadFile(path)
	if os.IsNotExist(err) {
		return &FormatHistory{}, nil
	}
	if err != nil {
		return nil, fmt.Errorf("ler format-history: %w", err)
	}
	var h FormatHistory
	if err := json.Unmarshal(data, &h); err != nil {
		return nil, fmt.Errorf("parsear format-history: %w", err)
	}
	return &h, nil
}

// SaveHistory writes _history/format-history.json atomically.
func SaveHistory(workspacePath string, h *FormatHistory) error {
	dir := filepath.Join(workspacePath, "_history")
	if err := os.MkdirAll(dir, 0755); err != nil {
		return fmt.Errorf("criar _history/: %w", err)
	}

	data, err := json.MarshalIndent(h, "", "  ")
	if err != nil {
		return fmt.Errorf("serializar history: %w", err)
	}

	path := filepath.Join(workspacePath, histRelPath)
	tmp := path + ".tmp"

	if err := os.WriteFile(tmp, data, 0644); err != nil {
		return fmt.Errorf("escrever tmp: %w", err)
	}
	if err := os.Rename(tmp, path); err != nil {
		os.Remove(tmp)
		return fmt.Errorf("rename tmp: %w", err)
	}
	return nil
}

// LastN returns the last n formats used (most recent first).
func (h *FormatHistory) LastN(n int) []string {
	var out []string
	for i, e := range h.History {
		if i >= n {
			break
		}
		out = append(out, e.Formato)
	}
	return out
}

// AddEntry prepends a new entry and trims to maxEntries.
func (h *FormatHistory) AddEntry(slug, formato string) {
	entry := HistoryEntry{
		Slug:    slug,
		Formato: formato,
		Data:    time.Now().Format("2006-01-02"),
	}
	h.History = append([]HistoryEntry{entry}, h.History...)
	if len(h.History) > maxEntries {
		h.History = h.History[:maxEntries]
	}
}