package workitem

import (
	"context"
	"encoding/json"
	"errors"
	"strings"
)

var ErrInvalidRef = errors.New("invalid workitem ref")

type ProviderID string

type Capability string

const (
	CapabilityLookup           Capability = "lookup"
	CapabilityComment          Capability = "comment"
	CapabilityStatusProjection Capability = "status_projection"
	CapabilityLabelProjection  Capability = "label_projection"
)

type Capabilities map[Capability]bool

func (c Capabilities) Supports(capability Capability) bool {
	return c[capability]
}

type Provider interface {
	ProviderID() ProviderID
	Capabilities() Capabilities
}

type Reader interface {
	FetchWorkItem(ctx context.Context, ref Ref) (WorkItem, error)
}

type Commenter interface {
	AppendComment(ctx context.Context, input CommentInput) error
}

type StatusProjector interface {
	ProjectStatus(ctx context.Context, input StatusProjection) error
}

type LabelProjector interface {
	ProjectLabels(ctx context.Context, input LabelProjection) error
}

type Ref struct {
	Provider ProviderID      `json:"provider"`
	Tenant   string          `json:"tenant"`
	Project  string          `json:"project"`
	ID       string          `json:"id"`
	URL      string          `json:"url,omitempty"`
	Metadata json.RawMessage `json:"metadata,omitempty"`
}

type WorkItem struct {
	Ref             Ref             `json:"ref"`
	Title           string          `json:"title"`
	DescriptionText string          `json:"description_text,omitempty"`
	DescriptionHTML string          `json:"description_html,omitempty"`
	State           string          `json:"state,omitempty"`
	AssigneeIDs     []string        `json:"assignee_ids,omitempty"`
	Labels          []string        `json:"labels,omitempty"`
	Metadata        json.RawMessage `json:"metadata,omitempty"`
}

type CommentFormat string

const (
	CommentFormatText     CommentFormat = "text"
	CommentFormatMarkdown CommentFormat = "markdown"
	CommentFormatHTML     CommentFormat = "html"
)

type CommentInput struct {
	Ref            Ref           `json:"ref"`
	Body           string        `json:"body"`
	Format         CommentFormat `json:"format"`
	ExternalSource string        `json:"external_source,omitempty"`
	ExternalID     string        `json:"external_id,omitempty"`
	Visibility     string        `json:"visibility,omitempty"`
}

type StatusProjection struct {
	Ref            Ref    `json:"ref"`
	CanonicalState string `json:"canonical_state"`
	ProviderState  string `json:"provider_state"`
}

type LabelTarget struct {
	Canonical string `json:"canonical"`
	Provider  string `json:"provider"`
}

type LabelProjection struct {
	Ref    Ref           `json:"ref"`
	Add    []LabelTarget `json:"add,omitempty"`
	Remove []LabelTarget `json:"remove,omitempty"`
}

type Mapping struct {
	States map[string]string `json:"states,omitempty"`
	Labels map[string]string `json:"labels,omitempty"`
}

func (m Mapping) StateTarget(canonical string) (string, bool) {
	target := strings.TrimSpace(m.States[strings.TrimSpace(canonical)])
	return target, target != ""
}

func (m Mapping) LabelTarget(canonical string) (string, bool) {
	target := strings.TrimSpace(m.Labels[strings.TrimSpace(canonical)])
	return target, target != ""
}

func NormalizeRef(ref Ref) (Ref, error) {
	provider := ProviderID(strings.TrimSpace(string(ref.Provider)))
	id := strings.TrimSpace(ref.ID)
	if provider == "" || id == "" {
		return Ref{}, ErrInvalidRef
	}

	meta := ref.Metadata
	if len(meta) == 0 {
		meta = json.RawMessage("{}")
	} else if !json.Valid(meta) {
		return Ref{}, ErrInvalidRef
	}

	return Ref{
		Provider: provider,
		Tenant:   strings.TrimSpace(ref.Tenant),
		Project:  strings.TrimSpace(ref.Project),
		ID:       id,
		URL:      strings.TrimSpace(ref.URL),
		Metadata: meta,
	}, nil
}