// ClawGo - Ultra-lightweight personal AI agent
// Inspired by and based on nanobot: https://github.com/HKUDS/nanobot
// License: MIT
//
// Copyright (c) 2026 ClawGo contributors

package agent

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

	"clawgo/pkg/config"
	"clawgo/pkg/logger"
)

// MemoryStore manages persistent memory for the agent.
// - Long-term memory: memory/MEMORY.md
// - Daily notes: memory/YYYYMM/YYYYMMDD.md
type MemoryStore struct {
	workspace        string
	memoryDir        string
	memoryFile       string
	layered          bool
	recentDays       int
	includeProfile   bool
	includeProject   bool
	includeProcedure bool
}

// NewMemoryStore creates a new MemoryStore with the given workspace path.
// It ensures the memory directory exists.
func NewMemoryStore(workspace string, cfg config.MemoryConfig) *MemoryStore {
	memoryDir := filepath.Join(workspace, "memory")
	memoryFile := filepath.Join(memoryDir, "MEMORY.md")

	// Ensure memory directory exists
	if err := os.MkdirAll(memoryDir, 0755); err != nil {
		logger.ErrorCF("memory", "Failed to create memory directory", map[string]interface{}{
			"memory_dir":      memoryDir,
			logger.FieldError: err.Error(),
		})
	}

	// Ensure MEMORY.md exists for first run (even without onboard).
	if _, err := os.Stat(memoryFile); os.IsNotExist(err) {
		initial := `# Long-term Memory

This file stores important information that should persist across sessions.

## User Information

(Important facts about user)

## Preferences

(User preferences learned over time)

## Important Notes

(Things to remember)
`
		if writeErr := os.WriteFile(memoryFile, []byte(initial), 0644); writeErr != nil {
			logger.ErrorCF("memory", "Failed to initialize MEMORY.md", map[string]interface{}{
				"memory_file":     memoryFile,
				logger.FieldError: writeErr.Error(),
			})
		}
	}

	if cfg.Layered {
		_ = os.MkdirAll(filepath.Join(memoryDir, "layers"), 0755)
		ensureLayerFile(filepath.Join(memoryDir, "layers", "profile.md"), "# User Profile\n\nStable user profile, preferences, identity traits.\n")
		ensureLayerFile(filepath.Join(memoryDir, "layers", "project.md"), "# Project Memory\n\nProject-specific architecture decisions and constraints.\n")
		ensureLayerFile(filepath.Join(memoryDir, "layers", "procedures.md"), "# Procedures Memory\n\nReusable workflows, command recipes, and runbooks.\n")
	}

	recentDays := cfg.RecentDays
	if recentDays <= 0 {
		recentDays = 3
	}

	return &MemoryStore{
		workspace:        workspace,
		memoryDir:        memoryDir,
		memoryFile:       memoryFile,
		layered:          cfg.Layered,
		recentDays:       recentDays,
		includeProfile:   cfg.Layers.Profile,
		includeProject:   cfg.Layers.Project,
		includeProcedure: cfg.Layers.Procedures,
	}
}

func ensureLayerFile(path, initial string) {
	if _, err := os.Stat(path); os.IsNotExist(err) {
		_ = os.WriteFile(path, []byte(initial), 0644)
	}
}

// getTodayFile returns the path to today's daily note file (memory/YYYYMM/YYYYMMDD.md).
func (ms *MemoryStore) getTodayFile() string {
	today := time.Now().Format("20060102") // YYYYMMDD
	monthDir := today[:6]                  // YYYYMM
	filePath := filepath.Join(ms.memoryDir, monthDir, today+".md")
	return filePath
}

// ReadLongTerm reads the long-term memory (MEMORY.md).
// Returns empty string if the file doesn't exist.
func (ms *MemoryStore) ReadLongTerm() string {
	if data, err := os.ReadFile(ms.memoryFile); err == nil {
		return string(data)
	}
	return ""
}

// WriteLongTerm writes content to the long-term memory file (MEMORY.md).
func (ms *MemoryStore) WriteLongTerm(content string) error {
	if err := os.MkdirAll(ms.memoryDir, 0755); err != nil {
		return err
	}
	return os.WriteFile(ms.memoryFile, []byte(content), 0644)
}

// ReadToday reads today's daily note.
// Returns empty string if the file doesn't exist.
func (ms *MemoryStore) ReadToday() string {
	todayFile := ms.getTodayFile()
	if data, err := os.ReadFile(todayFile); err == nil {
		return string(data)
	}
	return ""
}

// AppendToday appends content to today's daily note.
// If the file doesn't exist, it creates a new file with a date header.
func (ms *MemoryStore) AppendToday(content string) error {
	todayFile := ms.getTodayFile()

	// Ensure month directory exists
	monthDir := filepath.Dir(todayFile)
	if err := os.MkdirAll(monthDir, 0755); err != nil {
		return err
	}

	var existingContent string
	if data, err := os.ReadFile(todayFile); err == nil {
		existingContent = string(data)
	}

	var newContent string
	if existingContent == "" {
		// Add header for new day
		header := fmt.Sprintf("# %s\n\n", time.Now().Format("2006-01-02"))
		newContent = header + content
	} else {
		// Append to existing content
		newContent = existingContent + "\n" + content
	}

	return os.WriteFile(todayFile, []byte(newContent), 0644)
}

// GetRecentDailyNotes returns daily notes from the last N days.
// Contents are joined with "---" separator.
func (ms *MemoryStore) GetRecentDailyNotes(days int) string {
	var notes []string

	for i := 0; i < days; i++ {
		date := time.Now().AddDate(0, 0, -i)
		dateStr := date.Format("20060102") // YYYYMMDD
		monthDir := dateStr[:6]            // YYYYMM
		filePath := filepath.Join(ms.memoryDir, monthDir, dateStr+".md")

		if data, err := os.ReadFile(filePath); err == nil {
			notes = append(notes, string(data))
		}
	}

	if len(notes) == 0 {
		return ""
	}

	// Join with separator
	var result string
	for i, note := range notes {
		if i > 0 {
			result += "\n\n---\n\n"
		}
		result += note
	}
	return result
}

// GetMemoryContext returns formatted memory context for the agent prompt.
// Includes long-term memory and recent daily notes.
func (ms *MemoryStore) GetMemoryContext() string {
	var parts []string

	if ms.layered {
		layerParts := ms.getLayeredContext()
		parts = append(parts, layerParts...)
	}

	// Long-term memory
	longTerm := ms.ReadLongTerm()
	if longTerm != "" {
		parts = append(parts, "## Long-term Memory\n\n"+longTerm)
	}

	// Recent daily notes
	recentNotes := ms.GetRecentDailyNotes(ms.recentDays)
	if recentNotes != "" {
		parts = append(parts, "## Recent Daily Notes\n\n"+recentNotes)
	}

	if len(parts) == 0 {
		return ""
	}

	// Join parts with separator
	var result string
	for i, part := range parts {
		if i > 0 {
			result += "\n\n---\n\n"
		}
		result += part
	}
	return fmt.Sprintf("# Memory\n\n%s", result)
}

func (ms *MemoryStore) getLayeredContext() []string {
	parts := []string{}
	readLayer := func(filename, title string) {
		data, err := os.ReadFile(filepath.Join(ms.memoryDir, "layers", filename))
		if err != nil {
			return
		}
		content := string(data)
		if strings.TrimSpace(content) == "" {
			return
		}
		parts = append(parts, fmt.Sprintf("## %s\n\n%s", title, content))
	}

	if ms.includeProfile {
		readLayer("profile.md", "Memory Layer: Profile")
	}
	if ms.includeProject {
		readLayer("project.md", "Memory Layer: Project")
	}
	if ms.includeProcedure {
		readLayer("procedures.md", "Memory Layer: Procedures")
	}
	return parts
}