package config

import (
	"fmt"
	"os"
	"regexp"

	"github.com/BurntSushi/toml"
)

var timeFormatRe = regexp.MustCompile(`^\d{2}:\d{2}$`)

type Config struct {
	Memos    MemosConfig    `toml:"memos"`
	Database DatabaseConfig `toml:"database"`
	Search   SearchConfig   `toml:"search"`
	Telegram TelegramConfig `toml:"telegram"`
	Web      WebConfig      `toml:"web"`
	General  GeneralConfig  `toml:"general"`
}

type MemosConfig struct {
	URL       string `toml:"url"`
	Token     string `toml:"token"`
	PublicURL string `toml:"public_url"`
}

type DatabaseConfig struct {
	Path string `toml:"path"`
}

type SearchConfig struct {
	CooldownDays        int         `toml:"cooldown_days"`
	RelaxedCooldownDays int         `toml:"relaxed_cooldown_days"`
	PageSize            int         `toml:"page_size"`
	MaxYearsBack        int         `toml:"max_years_back"`
	PreferOlder         bool        `toml:"prefer_older"`
	TierWeights         TierWeights `toml:"tier_weights"`
}

type TierWeights struct {
	Tier1 int `toml:"tier1"`
	Tier2 int `toml:"tier2"`
	Tier3 int `toml:"tier3"`
	Tier4 int `toml:"tier4"`
	Tier5 int `toml:"tier5"`
	Tier6 int `toml:"tier6"`
	Tier7 int `toml:"tier7"`
}

func (tw TierWeights) Sum() int {
	return tw.Tier1 + tw.Tier2 + tw.Tier3 + tw.Tier4 + tw.Tier5 + tw.Tier6 + tw.Tier7
}

func (tw TierWeights) AsSlice() [7]int {
	return [7]int{tw.Tier1, tw.Tier2, tw.Tier3, tw.Tier4, tw.Tier5, tw.Tier6, tw.Tier7}
}

type TelegramConfig struct {
	Enabled bool   `toml:"enabled"`
	Token   string `toml:"token"`
	ChatID  int64  `toml:"chat_id"`
	SendAt  string `toml:"send_at"`
}

type WebConfig struct {
	Listen string `toml:"listen"`
}

type GeneralConfig struct {
	Timezone      string `toml:"timezone"`
	LogLevel      string `toml:"log_level"`
	AllowLoadMore bool   `toml:"allow_load_more"`
}

func Load(path string) (*Config, error) {
	data, err := os.ReadFile(path)
	if err != nil {
		return nil, fmt.Errorf("read config: %w", err)
	}

	var cfg Config
	if err := toml.Unmarshal(data, &cfg); err != nil {
		return nil, fmt.Errorf("parse config: %w", err)
	}

	setDefaults(&cfg)

	if err := validate(&cfg); err != nil {
		return nil, fmt.Errorf("validate config: %w", err)
	}

	return &cfg, nil
}

func setDefaults(cfg *Config) {
	if cfg.Database.Path == "" {
		cfg.Database.Path = "remembos.db"
	}
	if cfg.Search.CooldownDays == 0 {
		cfg.Search.CooldownDays = 90
	}
	if cfg.Search.RelaxedCooldownDays == 0 {
		cfg.Search.RelaxedCooldownDays = 30
	}
	if cfg.Search.PageSize == 0 {
		cfg.Search.PageSize = 50
	}
	if cfg.Search.MaxYearsBack == 0 {
		cfg.Search.MaxYearsBack = 10
	}
	if cfg.Search.TierWeights.Sum() == 0 {
		cfg.Search.TierWeights = TierWeights{
			Tier1: 35, Tier2: 15, Tier3: 15,
			Tier4: 12, Tier5: 10, Tier6: 5, Tier7: 8,
		}
	}
	if cfg.Web.Listen == "" {
		cfg.Web.Listen = "127.0.0.1:8080"
	}
	if cfg.General.Timezone == "" {
		cfg.General.Timezone = "Europe/Moscow"
	}
	if cfg.General.LogLevel == "" {
		cfg.General.LogLevel = "info"
	}
	if cfg.Telegram.SendAt == "" {
		cfg.Telegram.SendAt = "09:00"
	}
}

func validate(cfg *Config) error {
	if cfg.Memos.URL == "" {
		return fmt.Errorf("memos.url is required")
	}
	if cfg.Memos.Token == "" {
		return fmt.Errorf("memos.token is required")
	}
	if sum := cfg.Search.TierWeights.Sum(); sum != 100 {
		return fmt.Errorf("search.tier_weights must sum to 100, got %d", sum)
	}
	if cfg.Telegram.Enabled {
		if cfg.Telegram.Token == "" {
			return fmt.Errorf("telegram.token is required when telegram.enabled = true")
		}
		if cfg.Telegram.ChatID == 0 {
			return fmt.Errorf("telegram.chat_id is required when telegram.enabled = true")
		}
		if !timeFormatRe.MatchString(cfg.Telegram.SendAt) {
			return fmt.Errorf("telegram.send_at must be in HH:MM format, got %q", cfg.Telegram.SendAt)
		}
	}
	return nil
}