package main

import (
	"bytes"
	"encoding/json"
	"errors"
	"flag"
	"fmt"
	"os"
	"path/filepath"
	"regexp"
	"sort"
	"strings"

	"github.com/santhosh-tekuri/jsonschema/v6"
	"gopkg.in/yaml.v3"
)

var (
	// Config keys whose default value must never be a real credential.
	sensitiveKey = regexp.MustCompile(`(?i)(pass(word)?|secret|token|api[_-]?key|rcon)`)
	// A value made only of panel placeholders, e.g. "{saved:RCON_PASSWORD}".
	placeholderOnly = regexp.MustCompile(`^(\{[A-Za-z0-9_:.-]+\})+$`)
	// RFC 1918 addresses: home-lab and VPC details have no place in a public repo.
	privateIP = regexp.MustCompile(`\b(10\.\d{1,3}\.\d{1,3}\.\d{1,3}|192\.168\.\d{1,3}\.\d{1,3}|172\.(1[6-9]|2\d|3[01])\.\d{1,3}\.\d{1,3})\b`)
)

func runValidate(args []string) error {
	fs := flag.NewFlagSet("validate", flag.ExitOnError)
	gamesDir := fs.String("games", "games", "directory holding one folder per game")
	schemaDir := fs.String("schemas", "schema", "directory holding game.schema.json and test.schema.json")
	fs.Parse(args)

	gameSchema, err := compileSchema(filepath.Join(*schemaDir, "game.schema.json"))
	if err != nil {
		return err
	}
	testSchema, err := compileSchema(filepath.Join(*schemaDir, "test.schema.json"))
	if err != nil {
		return err
	}

	entries, err := os.ReadDir(*gamesDir)
	if err != nil {
		return err
	}
	failed, checked := 0, 0
	for _, e := range entries {
		if !e.IsDir() {
			continue
		}
		checked++
		problems := validateGame(filepath.Join(*gamesDir, e.Name()), e.Name(), gameSchema, testSchema)
		if len(problems) == 0 {
			fmt.Printf("ok    %s\n", e.Name())
			continue
		}
		failed++
		fmt.Printf("FAIL  %s\n", e.Name())
		for _, p := range problems {
			fmt.Printf("        - %s\n", p)
		}
	}
	if checked == 0 {
		return fmt.Errorf("no games found in %s", *gamesDir)
	}
	if failed > 0 {
		return fmt.Errorf("%d of %d games failed validation", failed, checked)
	}
	fmt.Printf("\nall %d games valid\n", checked)
	return nil
}

func validateGame(dir, folder string, gameSchema, testSchema *jsonschema.Schema) []string {
	var problems []string
	add := func(format string, a ...any) { problems = append(problems, fmt.Sprintf(format, a...)) }

	raw, err := os.ReadFile(filepath.Join(dir, "game.yaml"))
	if err != nil {
		return []string{"missing game.yaml"}
	}
	game, err := loadYAML(raw)
	if err != nil {
		return []string{"game.yaml: " + err.Error()}
	}
	if err := gameSchema.Validate(game); err != nil {
		add("game.yaml does not match schema:\n%s", indent(schemaErrors(err)))
		return problems // later checks assume the basic shape is right
	}
	g := game.(map[string]any)

	if g["id"] != folder {
		add("id %q must match folder name %q", g["id"], folder)
	}
	scanPrivateIPs(raw, "game.yaml", add)

	// Go's regexp is a subset of Java's, which the node-agent uses; anything that compiles here works there
	patterns, _ := g["failPatterns"].([]any)
	if p, ok := g["readyPattern"].(string); ok {
		patterns = append(patterns, p)
	}
	for _, p := range patterns {
		if _, err := regexp.Compile(fmt.Sprint(p)); err != nil {
			add("pattern %q does not compile: %v", p, err)
		}
	}

	defaults, _ := g["defaultConfig"].(map[string]any)
	props := schemaProperties(g)
	known := map[string]bool{}
	for k := range defaults {
		known[k] = true
	}
	for k := range props {
		known[k] = true
	}

	// publicIpConfigKey and maxPlayersConfigKey are injected by the panel, so only the map key must already exist.
	if key, ok := g["mapConfigKey"].(string); ok && key != "" && !known[key] {
		add("mapConfigKey %q is not in defaultConfig or configSchema", key)
	}

	for _, key := range sortedKeys(defaults) {
		if sensitiveKey.MatchString(key) && isCredential(defaults[key]) {
			add("defaultConfig.%s looks like a credential; leave it empty or use a placeholder like {saved:%s}", key, key)
		}
	}
	for _, key := range sortedKeys(props) {
		prop, _ := props[key].(map[string]any)
		if sensitiveKey.MatchString(key) && isCredential(prop["default"]) {
			add("configSchema.properties.%s.default looks like a credential; leave it empty", key)
		}
	}

	for _, key := range sortedKeys(props) {
		prop, _ := props[key].(map[string]any)
		if c, ok := prop["x-consent"]; !ok || c == false {
			continue
		}
		if truthy(prop["default"]) || truthy(defaults[key]) {
			add("consent %q must not default to true: users have to accept it themselves", key)
		}
	}

	testRaw, err := os.ReadFile(filepath.Join(dir, "test.yaml"))
	if errors.Is(err, os.ErrNotExist) {
		return problems
	}
	if err != nil {
		add("test.yaml: %v", err)
		return problems
	}
	test, err := loadYAML(testRaw)
	if err != nil {
		add("test.yaml: %v", err)
		return problems
	}
	if err := testSchema.Validate(test); err != nil {
		add("test.yaml does not match schema:\n%s", indent(schemaErrors(err)))
		return problems
	}
	scanPrivateIPs(testRaw, "test.yaml", add)
	t := test.(map[string]any)
	cfg, _ := t["config"].(map[string]any)
	secrets, _ := t["secrets"].(map[string]any)
	for _, key := range sortedKeys(cfg) {
		if !known[key] {
			add("test.yaml config.%s is not a key of this game", key)
		}
		if sensitiveKey.MatchString(key) {
			add("test.yaml config.%s looks like a credential; remove it (boot tests fill password settings with a throwaway "+
				"value), or, only if the server can't start without a real one, map it under 'secrets' to a CI secret", key)
		}
	}
	for _, key := range sortedKeys(secrets) {
		if !known[key] {
			add("test.yaml secrets.%s is not a key of this game", key)
		}
	}
	if example, ok := t["readyExample"].(string); ok {
		pattern, _ := g["readyPattern"].(string)
		if re, err := regexp.Compile(pattern); pattern == "" || err != nil {
			add("test.yaml has a readyExample but the game has no valid readyPattern")
		} else if !re.MatchString(example) {
			add("readyPattern %q does not match test.yaml readyExample %q", pattern, example)
		}
	}
	return problems
}

func compileSchema(path string) (*jsonschema.Schema, error) {
	raw, err := os.ReadFile(path)
	if err != nil {
		return nil, err
	}
	doc, err := jsonschema.UnmarshalJSON(bytes.NewReader(raw))
	if err != nil {
		return nil, fmt.Errorf("%s: %w", path, err)
	}
	id, _ := doc.(map[string]any)["$id"].(string)
	if id == "" {
		return nil, fmt.Errorf("%s: missing $id", path)
	}
	c := jsonschema.NewCompiler()
	if err := c.AddResource(id, doc); err != nil {
		return nil, err
	}
	return c.Compile(id)
}

// loadYAML decodes YAML into the JSON data model the schema validator expects.
func loadYAML(raw []byte) (any, error) {
	var v any
	if err := yaml.Unmarshal(raw, &v); err != nil {
		return nil, err
	}
	if v == nil {
		return nil, errors.New("file is empty")
	}
	j, err := json.Marshal(v)
	if err != nil {
		return nil, err
	}
	return jsonschema.UnmarshalJSON(bytes.NewReader(j))
}

func schemaProperties(g map[string]any) map[string]any {
	s, _ := g["configSchema"].(map[string]any)
	p, _ := s["properties"].(map[string]any)
	return p
}

func scanPrivateIPs(raw []byte, file string, add func(string, ...any)) {
	for i, line := range strings.Split(string(raw), "\n") {
		if ip := privateIP.FindString(line); ip != "" {
			add("%s line %d contains private address %s", file, i+1, ip)
		}
	}
}

func schemaErrors(err error) string {
	var ve *jsonschema.ValidationError
	if errors.As(err, &ve) {
		return fmt.Sprintf("%v", ve)
	}
	return err.Error()
}

func indent(s string) string {
	return "          " + strings.ReplaceAll(strings.TrimSpace(s), "\n", "\n          ")
}

func isCredential(v any) bool {
	s, ok := v.(string)
	return ok && s != "" && !placeholderOnly.MatchString(s)
}

func truthy(v any) bool {
	switch x := v.(type) {
	case bool:
		return x
	case string:
		return strings.EqualFold(strings.TrimSpace(x), "true")
	}
	return false
}

func sortedKeys(m map[string]any) []string {
	keys := make([]string, 0, len(m))
	for k := range m {
		keys = append(keys, k)
	}
	sort.Strings(keys)
	return keys
}