package config

import (
	"bytes"
	"fmt"
	"math"
	"sort"
	"strings"
	"unicode"

	configkit "gitea.maximumdirect.net/eric/ConfigKit"
	"gitea.maximumdirect.net/eric/narratio/internal/artifactpolicy"
	"gopkg.in/yaml.v3"
)

const (
	// PartySchemaVersion identifies the canonical campaign party document.
	PartySchemaVersion = "narratio.party.v1"
	// PlayersSchemaVersion identifies the derived players-only document.
	PlayersSchemaVersion = "narratio.players.v1"
)

// CanonicalParty is the normalized domain value for narratio.party.v1. Raw is
// retained independently so later preparation can copy the authored party file
// byte-for-byte rather than serializing normalized values.
type CanonicalParty struct {
	Raw        []byte
	Characters []PartyCharacter
}

// PartyCharacter is one ordered character declaration from a canonical party.
type PartyCharacter struct {
	ID        string
	Player    PartyPlayer
	Character PartyCharacterDetails
}

// PartyPlayer identifies the player controlling a character.
type PartyPlayer struct {
	Name string
}

// PartyCharacterDetails contains the player-facing character details.
type PartyCharacterDetails struct {
	Name    string
	Aliases []string
	Classes []PartyClass
}

// PartyClass represents one declared class. A missing Level is distinct from
// an explicitly supplied level.
type PartyClass struct {
	Name  string
	Level *int
}

type partyDocument struct {
	SchemaVersion string                    `yaml:"schema_version"`
	Characters    map[string]partyCharacter `yaml:"characters"`
}

type partyCharacter struct {
	Player    partyPlayer           `yaml:"player"`
	Character partyCharacterDetails `yaml:"character"`
}

type partyPlayer struct {
	Name string `yaml:"name"`
}

type partyCharacterDetails struct {
	Name    string       `yaml:"name"`
	Aliases []string     `yaml:"alias"`
	Classes []partyClass `yaml:"classes"`
}

type partyClass struct {
	Name  string `yaml:"name"`
	Level *int   `yaml:"level"`
}

type partyDomainError struct {
	path    configkit.Path
	message string
}

// ParseParty strictly parses one supported party document through ConfigKit.
func ParseParty(data []byte) (*CanonicalParty, error) {
	if int64(len(data)) > maxConfigDocumentBytes {
		return nil, fmt.Errorf("parse party config: party document exceeds %d-byte limit", maxConfigDocumentBytes)
	}
	definition := configkit.Definition[partyDocument]{
		Version: &configkit.VersionRule{
			Path:  configkit.Keys("schema_version"),
			Check: validatePartyVersion,
		},
		Validate: validatePartyDocument,
	}
	result, err := configkit.Load(configkit.Bytes("party.yml", data), configkit.Options[partyDocument]{Definition: definition})
	if err != nil {
		return nil, describeConfigKitLoadError("party", err)
	}
	return canonicalPartyFromResult(result, data), nil
}

func validatePartyVersion(version configkit.Version, validation *configkit.Validation) error {
	path := configkit.Keys("schema_version")
	if !version.Present || version.Null || version.Text == "" {
		validation.Error(path, fmt.Sprintf("schema_version is required; supported schema_version is %q", PartySchemaVersion))
	} else if version.Text != PartySchemaVersion {
		validation.Error(path, fmt.Sprintf("schema_version is unsupported; supported schema_version is %q", PartySchemaVersion))
	}
	return nil
}

func validatePartyDocument(document *partyDocument, validation *configkit.Validation) {
	if problem := firstPartyDomainError(document); problem != nil {
		validation.Error(problem.path, problem.message)
	}
}

func firstPartyDomainError(document *partyDocument) *partyDomainError {
	charactersPath := configkit.Keys("characters")
	if document == nil || len(document.Characters) == 0 {
		return &partyDomainError{path: charactersPath, message: "characters must be non-empty"}
	}
	ids := make([]string, 0, len(document.Characters))
	for id := range document.Characters {
		ids = append(ids, id)
	}
	sort.Strings(ids)
	seenNames := make([]string, 0, len(ids)*2)
	for _, id := range ids {
		path := charactersPath.Key(id)
		character := document.Characters[id]
		if id != strings.TrimSpace(id) || !artifactpolicy.IsConfiguredKey(id) {
			return &partyDomainError{path: path, message: "invalid character id"}
		}
		if err := validatePartyDisplayName(character.Player.Name); err != "" {
			return &partyDomainError{path: path.Key("player").Key("name"), message: err}
		}
		if err := validatePartyDisplayName(character.Character.Name); err != "" {
			return &partyDomainError{path: path.Key("character").Key("name"), message: err}
		}
		if partyNameAmbiguous(character.Character.Name, seenNames) {
			return &partyDomainError{path: path.Key("character").Key("name"), message: "name or alias is ambiguous"}
		}
		visibleNames := append(append([]string(nil), seenNames...), character.Character.Name)
		for index, alias := range character.Character.Aliases {
			aliasPath := path.Key("character").Key("alias").Index(index)
			if err := validatePartyDisplayName(alias); err != "" {
				return &partyDomainError{path: aliasPath, message: err}
			}
			if partyNameAmbiguous(alias, visibleNames) {
				return &partyDomainError{path: aliasPath, message: "name or alias is ambiguous"}
			}
			visibleNames = append(visibleNames, alias)
		}
		classesPath := path.Key("character").Key("classes")
		if len(character.Character.Classes) == 0 {
			return &partyDomainError{path: classesPath, message: "classes must be a non-empty list"}
		}
		classNames := make([]string, 0, len(character.Character.Classes))
		for index, class := range character.Character.Classes {
			classPath := classesPath.Index(index)
			if err := validatePartyDisplayName(class.Name); err != "" {
				return &partyDomainError{path: classPath.Key("name"), message: err}
			}
			if partyNameAmbiguous(class.Name, classNames) {
				return &partyDomainError{path: classPath.Key("name"), message: "duplicate class"}
			}
			classNames = append(classNames, class.Name)
			if class.Level != nil && *class.Level <= 0 {
				return &partyDomainError{path: classPath.Key("level"), message: "level must be a positive integer"}
			}
		}
		seenNames = visibleNames
	}
	return nil
}

func validatePartyDisplayName(value string) string {
	if value == "" || strings.TrimSpace(value) != value {
		return "display name must be non-empty and trimmed"
	}
	for _, runeValue := range value {
		if unicode.IsControl(runeValue) {
			return "display name must not contain control characters"
		}
	}
	return ""
}

func partyNameAmbiguous(name string, existing []string) bool {
	for _, candidate := range existing {
		if strings.EqualFold(name, candidate) {
			return true
		}
	}
	return false
}

func canonicalPartyFromResult(result *configkit.Result[partyDocument], raw []byte) *CanonicalParty {
	type orderedCharacter struct {
		id       string
		location configkit.Location
	}
	metadata := result.Metadata()
	ordered := make([]orderedCharacter, 0, len(result.Config.Characters))
	for id := range result.Config.Characters {
		entry := orderedCharacter{id: id, location: configkit.Location{Line: math.MaxInt}}
		if info, ok := metadata.Lookup(configkit.Keys("characters", id)); ok && len(info.Origin.Locations) != 0 {
			entry.location = info.Origin.Locations[0]
		}
		ordered = append(ordered, entry)
	}
	sort.Slice(ordered, func(left, right int) bool {
		if ordered[left].location.Line != ordered[right].location.Line {
			return ordered[left].location.Line < ordered[right].location.Line
		}
		if ordered[left].location.Column != ordered[right].location.Column {
			return ordered[left].location.Column < ordered[right].location.Column
		}
		return ordered[left].id < ordered[right].id
	})
	party := &CanonicalParty{Raw: bytes.Clone(raw), Characters: make([]PartyCharacter, 0, len(ordered))}
	for _, orderedCharacter := range ordered {
		input := result.Config.Characters[orderedCharacter.id]
		classes := make([]PartyClass, len(input.Character.Classes))
		for index, class := range input.Character.Classes {
			classes[index] = PartyClass{Name: class.Name, Level: class.Level}
		}
		party.Characters = append(party.Characters, PartyCharacter{
			ID:     orderedCharacter.id,
			Player: PartyPlayer{Name: input.Player.Name},
			Character: PartyCharacterDetails{
				Name: input.Character.Name, Aliases: append([]string(nil), input.Character.Aliases...), Classes: classes,
			},
		})
	}
	return party
}

// ClassSummary preserves the declaration order required by the party contract.
func (c PartyCharacter) ClassSummary() string {
	parts := make([]string, 0, len(c.Character.Classes))
	for _, class := range c.Character.Classes {
		entry := class.Name
		if class.Level != nil {
			entry += fmt.Sprintf(" %d", *class.Level)
		}
		parts = append(parts, entry)
	}
	return strings.Join(parts, " / ")
}

// AliasSummary preserves the declaration order required by the party contract.
func (c PartyCharacter) AliasSummary() string {
	return strings.Join(c.Character.Aliases, ", ")
}

// PlayersYAML renders the deterministic players-only projection of a
// canonical party. It returns one final newline, as produced by yaml.Marshal.
func (p *CanonicalParty) PlayersYAML() ([]byte, error) {
	if p == nil {
		return nil, fmt.Errorf("canonical party is required")
	}
	characters := append([]PartyCharacter(nil), p.Characters...)
	sort.Slice(characters, func(left, right int) bool {
		return characters[left].ID < characters[right].ID
	})
	type projectionCharacter struct {
		ID      string   `yaml:"id"`
		Name    string   `yaml:"name"`
		Aliases []string `yaml:"alias,omitempty"`
	}
	type projectionPlayer struct {
		Name      string              `yaml:"name"`
		Character projectionCharacter `yaml:"character"`
	}
	projection := struct {
		SchemaVersion string             `yaml:"schema_version"`
		Players       []projectionPlayer `yaml:"players"`
	}{SchemaVersion: PlayersSchemaVersion, Players: make([]projectionPlayer, 0, len(characters))}
	for _, character := range characters {
		projection.Players = append(projection.Players, projectionPlayer{
			Name: character.Player.Name,
			Character: projectionCharacter{
				ID: character.ID, Name: character.Character.Name,
				Aliases: append([]string(nil), character.Character.Aliases...),
			},
		})
	}
	encoded, err := yaml.Marshal(projection)
	if err != nil {
		return nil, fmt.Errorf("render players projection: %w", err)
	}
	return encoded, nil
}