// Package routing holds the per-user routing profile (可配置分流): the rule
// model, persistence (Store), and — in later tasks — validation and sing-box
// config rendering.
package routing

import (
	"net"
	"strings"
)

// Rule is a single user-authored routing rule (domain/IP/geosite match →
// proxy/direct action). Validation of Type/Action/Value lives in Task 2.
type Rule struct {
	Type    string `json:"type"`
	Value   string `json:"value"`
	Action  string `json:"action"`
	Note    string `json:"note,omitempty"`
	Enabled bool   `json:"enabled"`
}

// Builtin toggles the built-in routing behaviors that previously were
// hardcoded into the server's sing-box config rendering.
type Builtin struct {
	ChinaDirect      bool `json:"china_direct"`
	LanDirect        bool `json:"lan_direct"`
	PrivateViaTunnel bool `json:"private_via_tunnel"`
}

// Profile is a user's full routing configuration, persisted as JSON in
// routing_profiles.profile_json.
type Profile struct {
	Mode    string  `json:"mode"` // rule | global | direct
	Builtin Builtin `json:"builtin"`
	Rules   []Rule  `json:"rules"`
	Final   string  `json:"final"` // proxy | direct
}

// Default is the fail-safe fallback profile, equivalent to today's hardcoded
// behavior (smart routing + China direct + no user rules).
func Default() *Profile {
	return &Profile{
		Mode:    "rule",
		Builtin: Builtin{ChinaDirect: true, LanDirect: true, PrivateViaTunnel: true},
		Rules:   []Rule{},
		Final:   "proxy",
	}
}

// FieldError describes a single validation failure. Index is the offending
// rule's position in Profile.Rules, or -1 for profile-level fields
// (mode/final/rules count).
type FieldError struct {
	Index  int    `json:"index"`
	Field  string `json:"field"`
	Reason string `json:"reason"`
}

// MaxRules is the upper bound on the number of rules a profile may hold.
const MaxRules = 200

var validType = map[string]bool{"domain": true, "domain_suffix": true, "domain_keyword": true, "ip_cidr": true, "geoip": true, "geosite": true}
var validAction = map[string]bool{"direct": true, "proxy": true, "reject": true}
var geoWhitelist = map[string]bool{"cn": true} // geoip/geosite 仅自托管 cn

// Validate checks the profile against the type/action whitelist, CIDR
// syntax, the geo set whitelist, and the rule count cap. It returns an empty
// (nil) slice when the profile is valid; every violation is reported
// independently (no short-circuiting) so callers can surface all errors at
// once.
func (p *Profile) Validate() []FieldError {
	var errs []FieldError
	if p.Mode != "rule" && p.Mode != "global" && p.Mode != "direct" {
		errs = append(errs, FieldError{-1, "mode", "must be rule|global|direct"})
	}
	if p.Final != "proxy" && p.Final != "direct" {
		errs = append(errs, FieldError{-1, "final", "must be proxy|direct"})
	}
	if len(p.Rules) > MaxRules {
		errs = append(errs, FieldError{-1, "rules", "exceeds max 200"})
	}
	for i, r := range p.Rules {
		if !validType[r.Type] {
			errs = append(errs, FieldError{i, "type", "invalid type"})
		}
		if !validAction[r.Action] {
			errs = append(errs, FieldError{i, "action", "invalid action"})
		}
		if r.Value == "" {
			errs = append(errs, FieldError{i, "value", "empty"})
		}
		switch r.Type {
		case "ip_cidr":
			if _, _, err := net.ParseCIDR(r.Value); err != nil {
				errs = append(errs, FieldError{i, "value", "invalid CIDR"})
			}
		case "geoip", "geosite":
			if !geoWhitelist[strings.ToLower(r.Value)] {
				errs = append(errs, FieldError{i, "value", "geo set not in whitelist (cn only)"})
			}
		}
	}
	return errs
}

// Normalize trims rule values and de-duplicates rules by (type, value,
// action), keeping the first occurrence's position (and its Note/Enabled).
func (p *Profile) Normalize() {
	seen := map[string]bool{}
	out := p.Rules[:0]
	for _, r := range p.Rules {
		r.Value = strings.TrimSpace(r.Value)
		k := r.Type + "|" + r.Value + "|" + r.Action
		if seen[k] {
			continue
		}
		seen[k] = true
		out = append(out, r)
	}
	p.Rules = out
}