package config

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

	"github.com/BurntSushi/toml"
)

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

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

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

// AuthConfig wires Pete's web UI to an OIDC provider (our Authentik instance).
// When enabled, signed-in users get their preferences stored server-side keyed
// by the OIDC subject; anonymous visitors keep using browser localStorage.
type AuthConfig struct {
	Enabled       bool   `toml:"enabled"`
	Issuer        string `toml:"issuer"` // e.g. https://authentik.parodia.dev/application/o/pete/
	ClientID      string `toml:"client_id"`
	ClientSecret  string `toml:"client_secret"`
	RedirectURL   string `toml:"redirect_url"`   // e.g. https://news.parodia.dev/auth/callback
	SessionSecret string `toml:"session_secret"` // HMAC key for signing the session cookie
}

type MatrixConfig struct {
	Homeserver  string            `toml:"homeserver"`
	UserID      string            `toml:"user_id"`
	Password    string            `toml:"password"`
	PickleKey   string            `toml:"pickle_key"`
	DisplayName string            `toml:"display_name"`
	DataDir     string            `toml:"data_dir"`
	AdminRoom   string            `toml:"admin_room"`
	Channels    map[string]string `toml:"channels"`
	// Admins is the allowlist of Matrix user IDs permitted to run in-room
	// commands like !post. Empty means commands are disabled — the channel
	// rooms are public, so an empty list must NOT mean "anyone".
	Admins []string `toml:"admins"`
}

type PostingConfig struct {
	MinIntervalSeconds    int `toml:"min_interval_seconds"`
	BurstCapCount         int `toml:"burst_cap_count"`
	BurstCapWindowSeconds int `toml:"burst_cap_window_seconds"`
	DedupCooldownHours    int `toml:"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              `toml:"daily_cap_total"`
	RoundRobin    RoundRobinConfig `toml:"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 `toml:"enabled"`
	IntervalHours int  `toml:"interval_hours"`
}

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

type SourceConfig struct {
	Name                string `toml:"name"`
	FeedURL             string `toml:"feed_url"`
	Tier                int    `toml:"tier"`
	PollIntervalMinutes int    `toml:"poll_interval_minutes"`
	DirectRoute         string `toml:"direct_route"`
	Enabled             bool   `toml:"enabled"`
	// Language, when set, drops feed items whose per-item language tag is
	// present and does not match (prefix). Useful for multilingual feeds
	// like Politico Europe that publish English + French side-by-side.
	Language string `toml:"language"`
	// UserAgent overrides the User-Agent sent when fetching this feed. Empty
	// uses Pete's honest default bot UA. Set a browser-like string only for
	// sources whose WAF (e.g. AWS WAF on The Portugal News) blocks bot UAs.
	UserAgent string `toml:"user_agent"`
}

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 := toml.Decode(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")
	}
	// pickle_key encrypts the E2EE crypto store (olm/megolm + cross-signing
	// keys) at rest. Never fall back to a hardcoded default: a key baked into
	// the source is no protection if crypto.db ever leaks.
	if len(c.Matrix.PickleKey) < 16 {
		return fmt.Errorf("matrix.pickle_key must be set to a strong secret (>=16 chars); it encrypts the E2EE crypto store at rest")
	}
	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")
	}

	if c.Web.Auth.Enabled {
		a := c.Web.Auth
		if a.Issuer == "" || a.ClientID == "" || a.ClientSecret == "" || a.RedirectURL == "" {
			return fmt.Errorf("web.auth requires issuer, client_id, client_secret, and redirect_url when enabled")
		}
		if len(a.SessionSecret) < 16 {
			return fmt.Errorf("web.auth.session_secret must be at least 16 characters")
		}
	}

	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 {
			// Not a Matrix channel — treated as web-only (stories visible in the
			// UI but never posted). Warn so typos still surface.
			slog.Warn("source routes to non-Matrix channel (web-only)",
				"source", s.Name, "direct_route", 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.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
		}
	}
}