package daemon

import (
	"context"
	"crypto/rand"
	"encoding/json"
	"errors"
	"fmt"
	"io"
	"net/http"
	"reflect"
	"time"

	"albedo/cli/internal/daemon/protocol"
)

// OperationHandle freezes the chosen resource ID and exact admission payload.
// Retries always use this same input or session resource.
type OperationHandle struct {
	id        string
	operation operation
	kind      string
	sessionID string
}

func (handle *OperationHandle) ID() string       { return handle.id }
func (handle *OperationHandle) IsCreation() bool { return handle.kind == "creation" }

func operationID() (string, error) {
	var id [16]byte
	if _, err := rand.Read(id[:]); err != nil {
		return "", fmt.Errorf("create resource ID: %w", err)
	}
	stamp := uint64(time.Now().UnixMilli())
	for i := 5; i >= 0; i-- {
		id[i] = byte(stamp)
		stamp >>= 8
	}
	id[6] = id[6]&0x0f | 0x70
	id[8] = id[8]&0x3f | 0x80
	return fmt.Sprintf("%x-%x-%x-%x-%x", id[:4], id[4:6], id[6:8], id[8:10], id[10:]), nil
}

func NewSubmission(session string, fields SubmissionRequest) (*OperationHandle, error) {
	id := fields.SubmissionID
	if id == "" {
		var err error
		id, err = operationID()
		if err != nil {
			return nil, err
		}
	}
	kind := fields.Type
	if kind == "" || kind == "user" {
		kind = "message"
	}
	var body any
	switch kind {
	case "message":
		if fields.Content == nil {
			return nil, errors.New("message input requires text")
		}
		uploaded := make([]protocol.ImageUpload, len(fields.Images))
		for i, image := range fields.Images {
			uploaded[i] = protocol.ImageUpload{MimeType: string(image.MimeType), Data: image.Data}
		}
		body = protocol.MessageInputRequest{Kind: kind, Text: *fields.Content, Images: uploaded, Pastes: fields.Pastes, ClientID: optionalText(fields.ClientID)}
	case "continue":
		body = protocol.ContinueInputRequest{Kind: kind, ClientID: optionalText(fields.ClientID)}
	case "skill":
		body = protocol.SkillInputRequest{Kind: kind, CandidateID: fields.Name, CatalogRevision: fields.CatalogRevision, Arguments: fields.Arguments, ClientID: optionalText(fields.ClientID)}
	case "command":
		body = protocol.CommandInputRequest{Kind: kind, CommandID: fields.Name, Arguments: fields.CommandArguments, ClientID: optionalText(fields.ClientID)}
	default:
		return nil, fmt.Errorf("unknown input kind %q", kind)
	}
	payload, err := json.Marshal(body)
	if err != nil {
		return nil, err
	}
	handle := &OperationHandle{id: id, kind: kind, sessionID: session}
	handle.operation = operation{Name: "admit input", BuildRequest: func(base string, body io.Reader) (*http.Request, error) {
		return protocol.NewPutInputRequestWithBody(base, session, id, "application/json", body)
	}, Body: json.RawMessage(payload), Policy: receiptRecovery, Handle: handle}
	return handle, nil
}

func NewCreation(fields CreateSessionRequest) (*OperationHandle, error) {
	kind := fields.Kind
	if kind == "" {
		kind = "new"
	}
	var body any
	switch kind {
	case "new":
		body = protocol.NewSessionRequest{Kind: kind, Workspace: fields.Workspace, Name: optionalText(fields.Name), ProviderProfile: optionalText(fields.Provider), Model: optionalText(fields.Model), Effort: optionalText(fields.Effort)}
	case "fork":
		body = protocol.ForkSessionRequest{Kind: kind, SourceSessionID: fields.SourceSessionID, CheckpointID: fields.CheckpointID, Name: optionalText(fields.Name)}
	case "child":
		inputID, err := operationID()
		if err != nil {
			return nil, err
		}
		body = protocol.ChildSessionRequest{Kind: kind, ParentID: fields.ParentID, Address: fields.Address, Name: fields.Name, InitialInputID: inputID, Task: fields.Task, Model: optionalText(fields.Model), Effort: optionalText(fields.Effort)}
	default:
		return nil, fmt.Errorf("unknown creation kind %q", kind)
	}
	payload, err := json.Marshal(body)
	if err != nil {
		return nil, err
	}
	id, err := operationID()
	if err != nil {
		return nil, err
	}
	handle := &OperationHandle{id: id, kind: "creation", sessionID: id}
	handle.operation = operation{Name: "create session", BuildRequest: func(base string, body io.Reader) (*http.Request, error) {
		return protocol.NewCreateSessionRequestWithBody(base, id, &protocol.CreateSessionParams{IfNoneMatch: "*"}, "application/json", body)
	}, Body: json.RawMessage(payload), Headers: http.Header{"If-None-Match": {"*"}}, Policy: receiptRecovery, Handle: handle}
	return handle, nil
}

type InputReceipt protocol.Input

func (receipt InputReceipt) Rejection() error {
	if receipt.Admission != "rejected" {
		return nil
	}
	err := &APIError{StatusCode: int(receipt.HTTPStatus)}
	if receipt.Problem != nil {
		err.Code, err.Message = receipt.Problem.Code, receipt.Problem.Detail
		if err.Message == "" {
			err.Message = receipt.Problem.Title
		}
	}
	return err
}

func (receipt InputReceipt) Pending() bool { return value(receipt.Delivery) == "pending" }

func (receipt InputReceipt) Settled() bool {
	return value(receipt.Delivery) == "committed" || value(receipt.Delivery) == "cancelled"
}

func (receipt InputReceipt) InputOrder() int64 { return value(receipt.AcceptanceOrder) }

func (receipt InputReceipt) BlockingDetail() string {
	if receipt.BlockingReason != nil {
		return receipt.BlockingReason.Detail
	}
	return ""
}

func GetInput(ctx context.Context, conn *Connection, session, id string) (InputReceipt, error) {
	var input protocol.Input
	err := executeRead(ctx, conn, operation{Name: "read input", BuildRequest: func(base string, body io.Reader) (*http.Request, error) {
		return protocol.NewGetInputRequest(base, session, id)
	}, Policy: readRecovery}, func(data []byte) error {
		if err := decodeRequired(data, &input); err != nil {
			return err
		}
		if input.ID != id || input.SessionID != session {
			return fieldError("input identity")
		}
		return validInput(input)
	})
	if err != nil {
		return InputReceipt{}, err
	}
	return InputReceipt(input), nil
}
func validInput(input protocol.Input) error {
	if input.ID == "" || input.SessionID == "" {
		return fieldError("input identity")
	}
	switch input.Kind {
	case "message", "continue", "skill", "command":
	default:
		return fieldError("input kind")
	}
	if input.Admission == "accepted" {
		if input.HTTPStatus != 202 || input.AcceptedAt == nil || input.AcceptanceOrder == nil || *input.AcceptanceOrder < 1 || input.Problem != nil {
			return fieldError("input admission")
		}
		switch value(input.Delivery) {
		case "pending", "committed", "cancelled":
			return nil
		}
	} else if input.Admission == "rejected" && input.HTTPStatus >= 400 && input.HTTPStatus <= 599 && input.Problem != nil && input.Delivery == nil && input.AcceptedAt == nil && input.AcceptanceOrder == nil && input.Turn == nil {
		return nil
	}
	return fieldError("input admission")
}
func ResolveOperation(ctx context.Context, conn *Connection, handle *OperationHandle) (InputReceipt, error) {
	return GetInput(ctx, conn, handle.sessionID, handle.id)
}

// A found outcome is authoritative even when it rejects the input. A failed
// lookup leaves admission uncertain and may permit replay of the frozen request.
func executeReceipt[T any](ctx context.Context, conn *Connection, handle *OperationHandle, statuses []int, decode func([]byte, int) (T, error), resolve func(context.Context) (T, bool, error)) (T, error) {
	var result T
	if ctx == nil {
		ctx = context.Background()
	}
	ctx, cancel := context.WithTimeout(ctx, 20*time.Second)
	defer cancel()
	for attempt := range 2 {
		err := executeMutation(ctx, conn, handle.operation, statuses, func(body []byte, status int) error {
			var decodeErr error
			result, decodeErr = decode(body, status)
			return decodeErr
		})
		if err == nil {
			return result, nil
		}
		var uncertain *UncertainOutcomeError
		collision := false
		if api, ok := errors.AsType[*APIError](err); ok {
			collision = handle.kind == "creation" && api.StatusCode == 412
		}
		if !errors.As(err, &uncertain) && !collision {
			return result, err
		}
		if ctx.Err() != nil {
			return result, uncertainOperation(handle.operation, err)
		}
		resolved, found, lookupErr := resolve(ctx)
		if found {
			return resolved, lookupErr
		}
		if IsOperationExpired(lookupErr) {
			return result, uncertainOperation(handle.operation, lookupErr)
		}
		if handle.kind == "creation" {
			if api, ok := errors.AsType[*APIError](lookupErr); ok {
				if api.Code == "creation_conflict" {
					return result, lookupErr
				}
				if len(api.Decision) > 0 && api.StatusCode >= 400 && api.StatusCode < 500 && api.StatusCode != 404 {
					return result, lookupErr
				}
			}
		}
		if attempt == 1 {
			return result, uncertainOperation(handle.operation, err)
		}
	}
	panic("unreachable admission retry budget")
}
func ResolveCreation(ctx context.Context, conn *Connection, handle *OperationHandle) (Session, error) {
	session, err := GetSession(ctx, conn, handle.id)
	if err != nil {
		if api, ok := errors.AsType[*APIError](err); ok && len(api.Decision) > 0 {
			var decision protocol.CreationDecision
			if parseErr := decodeRequired(api.Decision, &decision); parseErr != nil {
				return Session{}, &ProtocolError{Code: "invalid_response", Operation: "read creation decision", Cause: parseErr}
			}
			if decision.Kind != "creation" || decision.SessionID != handle.ID() {
				return Session{}, fieldError("creation decision identity")
			}
			if decision.Creation != nil && !sameCreationIntent(handle.operation.Body.(json.RawMessage), decision.Creation.Submitted) {
				return Session{}, &APIError{StatusCode: 409, Code: "creation_conflict", Message: "the session ID belongs to another creation intent"}
			}
		}
		return Session{}, err
	}
	if session.wire.Creation == nil {
		return Session{}, fieldError("creation")
	}
	if !sameCreationIntent(handle.operation.Body.(json.RawMessage), session.wire.Creation.Submitted) {
		return Session{}, &APIError{StatusCode: 409, Code: "creation_conflict", Message: "the session ID belongs to another creation intent"}
	}

	return session, nil
}
func IsOperationExpired(err error) bool {
	api, ok := errors.AsType[*APIError](err)
	return ok && api.StatusCode == http.StatusGone
}

func sameCreationIntent(expected, stored json.RawMessage) bool {
	var left, right map[string]any
	if json.Unmarshal(expected, &left) != nil || json.Unmarshal(stored, &right) != nil {
		return false
	}
	var optional []string
	switch left["kind"] {
	case "new":
		optional = []string{"name", "provider_profile", "model", "effort"}
	case "fork":
		optional = []string{"name"}
	case "child":
		optional = []string{"model", "effort"}
	}
	for _, key := range optional {
		if _, ok := left[key]; !ok {
			left[key] = nil
		}
	}
	return reflect.DeepEqual(left, right)
}