// Package config is the synchronization configuration given to the engine:
// the primary cluster, the targets with their mappings and policies, the
// replicated kinds and the object selection. It is built from the database of
// the web UI (internal/store); credentials are decrypted only in memory.
package config

import (
	"errors"
	"fmt"
	"net"
	"net/url"
	"path"
	"strings"
	"time"

	"pve-confsync/internal/adapter"
	"pve-confsync/internal/model"
	"pve-confsync/internal/pve"
	"pve-confsync/internal/sshx"
)

// Cluster is the connection to one PVE cluster: the API with the root@pam
// credentials and SSH as root on one node for what the API does not cover.
type Cluster struct {
	Name        string
	URL         string
	User        string // API user, root@pam
	Password    string // decrypted, never logged
	Fingerprint string // pinned TLS certificate (SHA-256)
	CAPEM       string // CA bundle, PEM
	Insecure    bool
	Timeout     string
	SSHHost     string // empty: the host of URL
	SSHPort     int
	SSHHostKey  string // pinned host key (authorized_keys format)
}

// Client is a target cluster with its mapping (kind -> id -> field -> value)
// and its own policy overrides.
type Client struct {
	Cluster
	Mapping  map[model.Kind]map[string]map[string]any
	Policies map[model.Kind]map[string]adapter.Policy
}

// Selection filters the objects of a kind with glob patterns on their id.
type Selection struct {
	Include []string `json:"include,omitempty"`
	Exclude []string `json:"exclude,omitempty"`
}

// Config is the whole synchronization: Reference is the primary cluster.
type Config struct {
	Reference Cluster
	Clients   []Client
	Kinds     []model.Kind
	Objects   map[model.Kind]Selection
	Policies  map[model.Kind]map[string]adapter.Policy
	Prune     bool
}

// Validate checks a configuration built elsewhere (web UI database, YAML import).
func (c *Config) Validate() error { return c.validate() }

func (c *Config) validate() error {
	var errs []error
	seen := map[string]bool{}
	all := append([]Cluster{c.Reference}, clusters(c.Clients)...)
	for i, cl := range all {
		if cl.Name == "" {
			errs = append(errs, fmt.Errorf("cluster #%d: name is required", i))
		}
		if seen[cl.Name] {
			errs = append(errs, fmt.Errorf("cluster %s: duplicate name", cl.Name))
		}
		seen[cl.Name] = true
	}
	for _, k := range c.Kinds {
		if _, err := adapter.ByKind(k); err != nil {
			errs = append(errs, err)
		}
		for _, d := range adapter.KindDeps[k] {
			if !c.HasKind(d) {
				errs = append(errs, fmt.Errorf("%s needs %s", k, d))
			}
		}
	}
	check := func(where string, p map[model.Kind]map[string]adapter.Policy) {
		for k, fields := range p {
			a, err := adapter.ByKind(k)
			if err != nil {
				errs = append(errs, fmt.Errorf("%s: %w", where, err))
				continue
			}
			for f, pol := range fields {
				switch pol {
				case adapter.Sync, adapter.Ignore, adapter.Override:
				default:
					errs = append(errs, fmt.Errorf("%s: %s.%s: unknown policy %q", where, k, f, pol))
				}
				if pol == adapter.Sync && a.Forbidden(f) {
					errs = append(errs, fmt.Errorf("%s: %s.%s cannot be synchronized", where, k, f))
				}
			}
		}
	}
	check("policies", c.Policies)
	for _, cl := range c.Clients {
		check("client "+cl.Name, cl.Policies)
		for k := range cl.Mapping {
			if _, err := adapter.ByKind(k); err != nil {
				errs = append(errs, fmt.Errorf("client %s mapping: %w", cl.Name, err))
			}
		}
	}
	return errors.Join(errs...)
}

func clusters(cs []Client) []Cluster {
	out := make([]Cluster, len(cs))
	for i, c := range cs {
		out[i] = c.Cluster
	}
	return out
}

// Client returns the client with this name.
func (c *Config) Client(name string) (*Client, bool) {
	for i := range c.Clients {
		if c.Clients[i].Name == name {
			return &c.Clients[i], true
		}
	}
	return nil, false
}

// PVE builds the API client of a cluster, with its SSH access when the host
// key is recorded.
func (cl Cluster) PVE() (*pve.Client, error) {
	var timeout time.Duration
	var err error
	if cl.Timeout != "" {
		if timeout, err = time.ParseDuration(cl.Timeout); err != nil {
			return nil, fmt.Errorf("cluster %s: timeout: %w", cl.Name, err)
		}
	}
	o := pve.Options{
		Name: cl.Name, BaseURL: cl.URL, User: cl.User, Password: cl.Password,
		CAPEM: []byte(cl.CAPEM), Fingerprint: cl.Fingerprint, Insecure: cl.Insecure, Timeout: timeout,
	}
	if cl.SSHHostKey != "" {
		sh, err := sshx.New(cl.SSHOptions())
		if err != nil {
			return nil, fmt.Errorf("cluster %s: %w", cl.Name, err)
		}
		o.Shell = sh
	}
	return pve.New(o)
}

// SSHOptions is the SSH access of the cluster: root on SSHHost, or on the host of the API URL.
func (cl Cluster) SSHOptions() sshx.Options {
	host := cl.SSHHost
	if host == "" {
		if u, err := url.Parse(cl.URL); err == nil {
			host = u.Hostname()
		}
	}
	return sshx.Options{Host: host, Port: cl.SSHPort, User: "root", Password: cl.Password, HostKey: cl.SSHHostKey}
}

// Policy resolves the policy of a field for a client: client policy, then
// global policy, then the adapter default. Forbidden fields are always ignored.
func (c *Config) Policy(cl *Client, a adapter.Adapter, field string) adapter.Policy {
	if a.Forbidden(field) {
		return adapter.Ignore
	}
	if cl != nil {
		if p, ok := cl.Policies[a.Kind()][field]; ok {
			return p
		}
	}
	if p, ok := c.Policies[a.Kind()][field]; ok {
		return p
	}
	return a.DefaultPolicy(field)
}

// Selected tells whether an object id is part of the synchronization.
func (c *Config) Selected(k model.Kind, id string) bool {
	s, ok := c.Objects[k]
	if !ok {
		return true
	}
	in := len(s.Include) == 0
	for _, p := range s.Include {
		if m, _ := path.Match(p, id); m {
			in = true
			break
		}
	}
	for _, p := range s.Exclude {
		if m, _ := path.Match(p, id); m {
			return false
		}
	}
	return in
}

// HasKind tells whether a kind is synchronized.
func (c *Config) HasKind(k model.Kind) bool {
	for _, x := range c.Kinds {
		if x == k {
			return true
		}
	}
	return false
}

// NormalizeURL trims the URL of a cluster and adds the PVE port (8006) when
// none is given: https://pve1 becomes https://pve1:8006.
func NormalizeURL(raw string) string {
	s := strings.TrimRight(strings.TrimSpace(raw), "/")
	u, err := url.Parse(s)
	if err != nil || u.Host == "" || u.Port() != "" {
		return s
	}
	u.Host = net.JoinHostPort(u.Hostname(), "8006")
	return u.String()
}