package config

import (
	"fmt"
	"log/slog"
	"os"
	"regexp"

	"gopkg.in/yaml.v3"
)

// envBracketRe matches only ${VAR} style env references, not bare $VAR.
var envBracketRe = regexp.MustCompile(`\$\{([^}]+)\}`)

type Config struct {
	Matrix  MatrixConfig   `yaml:"matrix"`
	Posting PostingConfig  `yaml:"posting"`
	Storage StorageConfig  `yaml:"storage"`
	Web     WebConfig      `yaml:"web"`
	Sources []SourceConfig `yaml:"sources"`
}

// WebConfig controls the read-only HTTP interface (news.parodia.dev style).
type WebConfig struct {
	Enabled    bool   `yaml:"enabled"`
	ListenAddr string `yaml:"listen_addr"` // e.g. ":8080" or "127.0.0.1:8080"
	SiteTitle  string `yaml:"site_title"`  // display name in the header
	BaseURL    string `yaml:"base_url"`    // public URL (used in metadata only)
}

type MatrixConfig struct {
	Homeserver  string            `yaml:"homeserver"`
	UserID      string            `yaml:"user_id"`
	Password    string            `yaml:"password"`
	PickleKey   string            `yaml:"pickle_key"`
	DisplayName string            `yaml:"display_name"`
	DataDir     string            `yaml:"data_dir"`
	AdminRoom   string            `yaml:"admin_room"`
	Channels    map[string]string `yaml:"channels"`
}

type PostingConfig struct {
	MinIntervalSeconds    int `yaml:"min_interval_seconds"`
	BurstCapCount         int `yaml:"burst_cap_count"`
	BurstCapWindowSeconds int `yaml:"burst_cap_window_seconds"`
	DedupCooldownHours    int `yaml:"dedup_cooldown_hours"`
	// DailyCapTotal is the hard global cap on posts across ALL channels in a
	// rolling 24-hour window. 0 disables the cap.
	DailyCapTotal int              `yaml:"daily_cap_total"`
	RoundRobin    RoundRobinConfig `yaml:"round_robin"`
}

// RoundRobinConfig switches Pete from immediate-on-classify posting to a
// paced rotation: one story per IntervalHours, picking the next channel in
// rotation order that has a postable story (skip-and-advance, newest-first).
type RoundRobinConfig struct {
	Enabled       bool `yaml:"enabled"`
	IntervalHours int  `yaml:"interval_hours"`
}

type StorageConfig struct {
	DBPath            string `yaml:"db_path"`
	RecentWindowHours int    `yaml:"recent_window_hours"`
}

type SourceConfig struct {
	Name                string `yaml:"name"`
	FeedURL             string `yaml:"feed_url"`
	Tier                int    `yaml:"tier"`
	PollIntervalMinutes int    `yaml:"poll_interval_minutes"`
	DirectRoute         string `yaml:"direct_route"`
	Enabled             bool   `yaml:"enabled"`
}

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

	// Expand only ${VAR} style env references, not bare $VAR
	// (bare $ in passwords like "pa$$word" must not be mangled)
	expanded := envBracketRe.ReplaceAllStringFunc(string(data), func(match string) string {
		varName := match[2 : len(match)-1] // strip ${ and }
		val := os.Getenv(varName)
		if val == "" {
			slog.Warn("config: env var referenced but not set", "var", varName)
		}
		return val
	})

	var cfg Config
	if err := yaml.Unmarshal([]byte(expanded), &cfg); err != nil {
		return nil, fmt.Errorf("parse config: %w", err)
	}

	cfg.applyDefaults()

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

	return &cfg, nil
}

func (c *Config) validate() error {
	if c.Matrix.Homeserver == "" {
		return fmt.Errorf("matrix.homeserver is required")
	}
	if c.Matrix.UserID == "" {
		return fmt.Errorf("matrix.user_id is required")
	}
	if c.Matrix.Password == "" {
		return fmt.Errorf("matrix.password is required")
	}
	if len(c.Matrix.Channels) == 0 {
		return fmt.Errorf("matrix.channels must have at least one entry")
	}
	if c.Storage.DBPath == "" {
		return fmt.Errorf("storage.db_path is required")
	}

	for i, s := range c.Sources {
		if s.Name == "" {
			return fmt.Errorf("sources[%d].name is required", i)
		}
		if s.FeedURL == "" {
			return fmt.Errorf("sources[%d].feed_url is required", i)
		}
		if s.Tier < 1 || s.Tier > 3 {
			return fmt.Errorf("sources[%d].tier must be 1-3", i)
		}
		if s.PollIntervalMinutes <= 0 {
			return fmt.Errorf("sources[%d].poll_interval_minutes must be > 0", i)
		}
		if !s.Enabled {
			continue
		}
		if s.DirectRoute == "" {
			return fmt.Errorf("sources[%d] (%s): direct_route is required for enabled sources", i, s.Name)
		}
		if _, ok := c.Matrix.Channels[s.DirectRoute]; !ok {
			return fmt.Errorf("sources[%d] (%s): direct_route %q is not a configured matrix.channels key", i, s.Name, s.DirectRoute)
		}
	}

	return nil
}

func (c *Config) applyDefaults() {
	if c.Matrix.DataDir == "" {
		c.Matrix.DataDir = "./data"
	}
	if c.Matrix.DisplayName == "" {
		c.Matrix.DisplayName = "Pete"
	}
	if c.Matrix.PickleKey == "" {
		c.Matrix.PickleKey = "pete_pickle_key"
	}
	if c.Posting.MinIntervalSeconds == 0 {
		c.Posting.MinIntervalSeconds = 300
	}
	if c.Posting.BurstCapCount == 0 {
		c.Posting.BurstCapCount = 3
	}
	if c.Posting.BurstCapWindowSeconds == 0 {
		c.Posting.BurstCapWindowSeconds = 1800
	}
	if c.Posting.DedupCooldownHours == 0 {
		c.Posting.DedupCooldownHours = 48
	}
	if c.Posting.RoundRobin.IntervalHours == 0 {
		c.Posting.RoundRobin.IntervalHours = 4
	}
	if c.Storage.RecentWindowHours == 0 {
		c.Storage.RecentWindowHours = 24
	}
	if c.Web.ListenAddr == "" {
		c.Web.ListenAddr = ":8080"
	}
	if c.Web.SiteTitle == "" {
		c.Web.SiteTitle = "Pete"
	}
	for i := range c.Sources {
		if c.Sources[i].PollIntervalMinutes == 0 {
			c.Sources[i].PollIntervalMinutes = 20
		}
	}
}