// Package validate runs startup integrity checks across all data files:
// duplicate IDs, referential integrity (rooms, mobs, objects, items, drops,
// courses, techs), and world wiring (orphan rooms). It depends only on the
// data packages (world, object, item, behavior), never on the game
// orchestrator, so it can be reused and tested in isolation.
package validate

import (
	"bytes"
	"fmt"
	"os"
	"path/filepath"
	"sort"
	"strconv"
	"strings"

	"gopkg.in/yaml.v3"

	"thehouseoficarus/internal/behavior"
	"thehouseoficarus/internal/cardart"
	"thehouseoficarus/internal/item"
	"thehouseoficarus/internal/object"
	"thehouseoficarus/internal/world"
)

// Issue is a single validation finding.
type Issue struct {
	Level   string // "ERROR" or "WARN"
	Type    string // "duplicate", "reference", "integrity"
	Message string
}

// CourseView is the subset of a course definition needed for validation.
type CourseView struct {
	ID            string
	StartRoom     int
	ObstacleRooms []int
}

// TechView is the subset of a tech definition needed for validation.
type TechView struct {
	ID        string
	Name      string
	DrainRate float64
}

// Source bundles everything the validator reads. The game package builds this
// from its stores and passes it to Run.
type Source struct {
	DataDir           string
	Items             *item.ItemStore
	Objects           *object.ObjectStore
	Mobs              *world.MobStore
	World             *world.World
	Courses           []CourseView
	Techs             []TechView
	TechIDs           map[string]bool
	RootRooms         []int
	IgnoreUnreachable []int
}

// Run executes all checks and returns the collected issues.
func Run(s Source) []Issue {
	var issues []Issue

	for _, dir := range []struct{ sub, label string }{
		{"items", "item"}, {"rooms", "room"}, {"mobs", "mob"},
		{"objects", "object"}, {"drops", "drop table"}, {"courses", "course"},
		{"modules", "module"}, {"techs", "tech"}, {"help", "help topic"},
		{"triggers", "trigger"},
	} {
		issues = append(issues, validateIDs(s.DataDir, dir.sub, dir.label)...)
	}

	issues = append(issues, validateKnownFields(s.DataDir)...)
	issues = append(issues, validateRoomFilenames(s.DataDir)...)

	issues = append(issues, validateRooms(s)...)
	issues = append(issues, validateMobs(s)...)
	issues = append(issues, validateHazards(s)...)
	issues = append(issues, validateObjects(s)...)
	issues = append(issues, validateItems(s)...)
	issues = append(issues, validateCraftBlocks(s)...)
	issues = append(issues, validateDropTables(s)...)
	issues = append(issues, validateCourses(s)...)
	issues = append(issues, validateRoomTriggers(s)...)
	issues = append(issues, validateTechs(s)...)
	issues = append(issues, validateRoomWiring(s)...)
	issues = append(issues, validateRoomGrid(s)...)
	issues = append(issues, validateExitReciprocity(s)...)

	return issues
}

// validateRoomFilenames flags room files whose name is not a plain integer:
// the room index only accepts numeric stems, so a file like
// "1001_copy.yaml" would otherwise be silently ignored (and, before the
// strconv fix, could shadow the real room 1001).
func validateRoomFilenames(dataDir string) []Issue {
	dir := filepath.Join(dataDir, "rooms")
	var issues []Issue
	_ = behavior.WalkYAMLDir(dir, func(path, id string, data []byte) error {
		if _, err := strconv.Atoi(id); err != nil {
			rel := strings.TrimPrefix(path, dataDir+"/")
			issues = append(issues, Issue{
				Level:   "ERROR",
				Type:    "integrity",
				Message: fmt.Sprintf("room %s: filename is not a numeric room ID and the file is ignored", rel),
			})
		}
		return nil
	})
	return issues
}

// validateKnownFields decodes every authored data file with KnownFields(true)
// so a misspelled or stale YAML key is a startup ERROR instead of being
// silently discarded by yaml.Unmarshal. Only package-owned content types are
// covered (world/object/item/behavior); game-owned definitions are checked by
// their own loaders.
func validateKnownFields(dataDir string) []Issue {
	targets := []struct {
		subDir string
		label  string
		newDef func() any
	}{
		{"rooms", "room", func() any { return new(world.Room) }},
		{"mobs", "mob", func() any { return new(world.MobDef) }},
		{"objects", "object", func() any { return new(object.ObjectDef) }},
		{"items", "item", func() any { return new(item.ItemDef) }},
		{"drops", "drop table", func() any { return new(behavior.DropTableDef) }},
		{"hazards", "hazard", func() any { return new(world.HazardDef) }},
	}
	var issues []Issue
	for _, t := range targets {
		dir := filepath.Join(dataDir, t.subDir)
		_ = behavior.WalkYAMLDir(dir, func(path, id string, data []byte) error {
			dec := yaml.NewDecoder(bytes.NewReader(data))
			dec.KnownFields(true)
			if err := dec.Decode(t.newDef()); err != nil {
				rel := strings.TrimPrefix(path, dataDir+"/")
				issues = append(issues, Issue{
					Level:   "ERROR",
					Type:    "unknown-field",
					Message: fmt.Sprintf("%s %s: %v", t.label, rel, err),
				})
			}
			return nil
		})
	}
	// cards.yaml lives at the data root rather than a subdirectory.
	if data, err := os.ReadFile(filepath.Join(dataDir, "cards.yaml")); err == nil {
		dec := yaml.NewDecoder(bytes.NewReader(data))
		dec.KnownFields(true)
		if err := dec.Decode(new(cardart.Store)); err != nil {
			issues = append(issues, Issue{
				Level:   "ERROR",
				Type:    "unknown-field",
				Message: fmt.Sprintf("cards.yaml: %v", err),
			})
		}
	}
	return issues
}

func validateIDs(dataDir, subDir, label string) []Issue {
	dir := filepath.Join(dataDir, subDir)
	dups := behavior.CheckDuplicateIDs(dir)
	var issues []Issue
	for _, d := range dups {
		short := make([]string, len(d.Paths))
		for i, p := range d.Paths {
			short[i] = strings.TrimPrefix(p, dir+"/")
		}
		issues = append(issues, Issue{
			Level: "ERROR",
			Type:  "duplicate",
			Message: fmt.Sprintf("Duplicate %s ID %q found in: %s",
				label, d.ID, strings.Join(short, ", ")),
		})
	}
	return issues
}

func dropTableIDSet(dataDir string) map[string]bool {
	dir := filepath.Join(dataDir, "drops")
	ids := make(map[string]bool)
	behavior.WalkYAMLDir(dir, func(path, id string, data []byte) error {
		ids[id] = true
		return nil
	})
	return ids
}

// LogIssues prints validation results to stderr, sorted with errors first.
func LogIssues(issues []Issue) {
	if len(issues) == 0 {
		fmt.Fprintf(os.Stderr, "Startup validation: OK\n")
		return
	}

	errors := 0
	warns := 0
	for _, issue := range issues {
		if issue.Level == "ERROR" {
			errors++
		} else {
			warns++
		}
	}

	fmt.Fprintf(os.Stderr, "\n=== Startup Validation: %d error(s), %d warning(s) ===\n\n", errors, warns)

	sort.Slice(issues, func(i, j int) bool {
		if issues[i].Level != issues[j].Level {
			return issues[i].Level == "ERROR"
		}
		return issues[i].Message < issues[j].Message
	})

	for _, issue := range issues {
		tag := fmt.Sprintf("[%s]", issue.Level)
		fmt.Fprintf(os.Stderr, "  %-7s %s\n", tag, issue.Message)
	}
	fmt.Fprintln(os.Stderr)

	if errors > 0 {
		fmt.Fprintf(os.Stderr, "*** %d startup errors detected. The server may behave unexpectedly. ***\n", errors)
	}
}

// reservedTechIDs are tech IDs whose semantics are coupled to code logic and
// must exist in YAML (damage protection mapping + death retribution).
var reservedTechIDs = map[string]bool{
	"protect_melee":   true,
	"protect_ranged":  true,
	"protect_science": true,
	"retribution":     true,
}