package mcp

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"strings"
	"time"

	"github.com/m/projax/store"
)

// RegisterProjaxTools wires every projax-flavoured tool onto an *mcp.Server.
// All tools delegate to *store.Store directly so business logic is shared
// with the web UI — no duplication.
func RegisterProjaxTools(s *Server, st *store.Store) {
	s.Register(Tool{
		Name:        "list_items",
		Description: "List projax items with optional filters (parent_path, tags, management, kind, status, q, has_repo, has_caldav).",
		InputSchema: json.RawMessage(`{
		  "type": "object",
		  "properties": {
		    "parent_path": {"type": "string", "description": "Match items whose paths array contains a path beginning with this prefix"},
		    "tags":        {"type": "array",  "items": {"type": "string"}, "description": "All tags must be present"},
		    "management":  {"type": "array",  "items": {"type": "string"}, "description": "All management modes must be present (e.g. ['mai'])"},
		    "kind":        {"type": "array",  "items": {"type": "string"}, "description": "Any of these kinds matches"},
		    "status":      {"type": "string"},
		    "q":           {"type": "string", "description": "Substring match against title/slug/aliases/content_md"},
		    "has_repo":    {"type": "boolean"},
		    "has_caldav":  {"type": "boolean"},
		    "limit":       {"type": "integer", "minimum": 0}
		  }
		}`),
		Handler: listItemsTool(st),
	})
	s.Register(Tool{
		Name:        "get_item",
		Description: "Fetch a single item by id, dot-path (e.g. 'dev.paliad'), or root slug. Multi-parent items resolve to the same row from any path.",
		InputSchema: json.RawMessage(`{
		  "type": "object",
		  "properties": {
		    "id":      {"type": "string", "description": "uuid"},
		    "path":    {"type": "string", "description": "Dot-path or slug"},
		    "include_links": {"type": "boolean", "description": "Include item_links in the response (default true)"}
		  }
		}`),
		Handler: getItemTool(st),
	})
	s.Register(Tool{
		Name:        "create_item",
		Description: "Create a new projax item. parent_paths is a string[] — pass [] for a root, ['work'] for single-parent, ['work','dev'] for multi-parent.",
		InputSchema: json.RawMessage(`{
		  "type": "object",
		  "required": ["slug", "title"],
		  "properties": {
		    "slug":         {"type": "string"},
		    "title":        {"type": "string"},
		    "parent_paths": {"type": "array", "items": {"type": "string"}},
		    "kind":         {"type": "array", "items": {"type": "string"}},
		    "tags":         {"type": "array", "items": {"type": "string"}},
		    "management":   {"type": "array", "items": {"type": "string"}},
		    "content_md":   {"type": "string"},
		    "status":       {"type": "string"},
		    "metadata":     {"type": "object"}
		  }
		}`),
		Handler: createItemTool(st),
	})
	s.Register(Tool{
		Name:        "update_item",
		Description: "Partial update of an existing item. Pass any subset of title/slug/content_md/status/tags/management/parent_paths/pinned/archived. parent_paths replaces the full parent list.",
		InputSchema: json.RawMessage(`{
		  "type": "object",
		  "properties": {
		    "id":           {"type": "string"},
		    "path":         {"type": "string"},
		    "title":        {"type": "string"},
		    "slug":         {"type": "string"},
		    "parent_paths": {"type": "array", "items": {"type": "string"}},
		    "content_md":   {"type": "string"},
		    "status":       {"type": "string"},
		    "pinned":       {"type": "boolean"},
		    "archived":     {"type": "boolean"},
		    "tags":         {"type": "array", "items": {"type": "string"}},
		    "management":   {"type": "array", "items": {"type": "string"}}
		  }
		}`),
		Handler: updateItemTool(st),
	})
	s.Register(Tool{
		Name:        "delete_item",
		Description: "Soft-delete an item. Refuses on live descendants unless cascade=true.",
		InputSchema: json.RawMessage(`{
		  "type": "object",
		  "properties": {
		    "id":       {"type": "string"},
		    "path":     {"type": "string"},
		    "cascade":  {"type": "boolean", "description": "Soft-delete every descendant too"}
		  }
		}`),
		Handler: deleteItemTool(st),
	})
	s.Register(Tool{
		Name:        "list_links",
		Description: "List item_links attached to one item.",
		InputSchema: json.RawMessage(`{
		  "type": "object",
		  "properties": {
		    "id":       {"type": "string"},
		    "path":     {"type": "string"},
		    "ref_type": {"type": "string", "description": "Optional ref_type filter (e.g. 'gitea-repo')"}
		  }
		}`),
		Handler: listLinksTool(st),
	})
	s.Register(Tool{
		Name:        "add_link",
		Description: "Add an external item_link to an item (caldav-list / gitea-repo / document / note / url / …). Pass event_date=YYYY-MM-DD to anchor a dated artifact (PER day-granular).",
		InputSchema: json.RawMessage(`{
		  "type": "object",
		  "required": ["ref_type", "ref_id"],
		  "properties": {
		    "id":         {"type": "string"},
		    "path":       {"type": "string"},
		    "ref_type":   {"type": "string"},
		    "ref_id":     {"type": "string"},
		    "rel":        {"type": "string", "description": "Relation, default 'contains'"},
		    "note":       {"type": "string"},
		    "event_date": {"type": "string", "description": "YYYY-MM-DD; day-granular anchor for PER-cited artifacts"},
		    "metadata":   {"type": "object"}
		  }
		}`),
		Handler: addLinkTool(st),
	})
	s.Register(Tool{
		Name:        "remove_link",
		Description: "Delete an item_link by id.",
		InputSchema: json.RawMessage(`{
		  "type": "object",
		  "required": ["link_id"],
		  "properties": {"link_id": {"type": "string"}}
		}`),
		Handler: removeLinkTool(st),
	})
	s.Register(Tool{
		Name:        "search",
		Description: "Ranked substring search across title/slug/aliases/content_md. Buckets: exact-slug → title-prefix → title-contains → alias → content.",
		InputSchema: json.RawMessage(`{
		  "type": "object",
		  "required": ["query"],
		  "properties": {
		    "query": {"type": "string"},
		    "limit": {"type": "integer", "minimum": 1, "maximum": 200}
		  }
		}`),
		Handler: searchTool(st),
	})
	s.Register(Tool{
		Name:        "tree",
		Description: "Return a nested tree of items. Multi-parent items appear under each ancestor branch.",
		InputSchema: json.RawMessage(`{
		  "type": "object",
		  "properties": {
		    "root_path": {"type": "string", "description": "Optional subtree root; default returns the whole forest"},
		    "depth":     {"type": "integer", "minimum": 0, "description": "Max depth (0 = unlimited)"}
		  }
		}`),
		Handler: treeTool(st),
	})
}

// itemView is the JSON shape returned to MCP clients. We hand-roll it so the
// field names stay snake_case and the *time.Time / *string nullability
// renders as JSON null instead of being skipped (omitempty would hide them).
type itemView struct {
	ID          string         `json:"id"`
	Kind        []string       `json:"kind"`
	Title       string         `json:"title"`
	Slug        string         `json:"slug"`
	Paths       []string       `json:"paths"`
	ParentIDs   []string       `json:"parent_ids"`
	ContentMD   string         `json:"content_md"`
	Aliases     []string       `json:"aliases"`
	Metadata    map[string]any `json:"metadata"`
	Status      string         `json:"status"`
	Pinned      bool           `json:"pinned"`
	Archived    bool           `json:"archived"`
	StartTime   any            `json:"start_time"`
	EndTime     any            `json:"end_time"`
	Source      string         `json:"source"`
	SourceRefID any            `json:"source_ref_id"`
	Tags        []string       `json:"tags"`
	Management  []string       `json:"management"`
	CreatedAt   string         `json:"created_at"`
	UpdatedAt   string         `json:"updated_at"`
	Links       []linkView     `json:"links,omitempty"`
}

type linkView struct {
	ID        string         `json:"id"`
	ItemID    string         `json:"item_id"`
	RefType   string         `json:"ref_type"`
	RefID     string         `json:"ref_id"`
	Rel       string         `json:"rel"`
	Note      any            `json:"note"`
	Metadata  map[string]any `json:"metadata"`
	CreatedAt string         `json:"created_at"`
	EventDate any            `json:"event_date"`
}

func toItemView(it *store.Item) itemView {
	v := itemView{
		ID:         it.ID,
		Kind:       sliceOr(it.Kind, []string{}),
		Title:      it.Title,
		Slug:       it.Slug,
		Paths:      sliceOr(it.Paths, []string{}),
		ParentIDs:  sliceOr(it.ParentIDs, []string{}),
		ContentMD:  it.ContentMD,
		Aliases:    sliceOr(it.Aliases, []string{}),
		Metadata:   mapOr(it.Metadata),
		Status:     it.Status,
		Pinned:     it.Pinned,
		Archived:   it.Archived,
		Source:     it.Source,
		Tags:       sliceOr(it.Tags, []string{}),
		Management: sliceOr(it.Management, []string{}),
		CreatedAt:  it.CreatedAt.UTC().Format("2006-01-02T15:04:05Z"),
		UpdatedAt:  it.UpdatedAt.UTC().Format("2006-01-02T15:04:05Z"),
	}
	if it.StartTime != nil {
		v.StartTime = it.StartTime.UTC().Format("2006-01-02T15:04:05Z")
	}
	if it.EndTime != nil {
		v.EndTime = it.EndTime.UTC().Format("2006-01-02T15:04:05Z")
	}
	if it.SourceRefID != nil {
		v.SourceRefID = *it.SourceRefID
	}
	return v
}

func toLinkView(l *store.ItemLink) linkView {
	v := linkView{
		ID:        l.ID,
		ItemID:    l.ItemID,
		RefType:   l.RefType,
		RefID:     l.RefID,
		Rel:       l.Rel,
		Metadata:  mapOr(l.Metadata),
		CreatedAt: l.CreatedAt.UTC().Format("2006-01-02T15:04:05Z"),
	}
	if l.Note != nil {
		v.Note = *l.Note
	}
	if l.EventDate != nil {
		v.EventDate = l.EventDate.UTC().Format("2006-01-02")
	}
	return v
}

func sliceOr[T any](v []T, fallback []T) []T {
	if v == nil {
		return fallback
	}
	return v
}
func mapOr(v map[string]any) map[string]any {
	if v == nil {
		return map[string]any{}
	}
	return v
}

// resolveItem turns an id-or-path argument pair into a concrete *store.Item.
func resolveItem(ctx context.Context, st *store.Store, id, path string) (*store.Item, error) {
	id = strings.TrimSpace(id)
	path = strings.TrimSpace(path)
	if id != "" {
		return st.GetByID(ctx, id)
	}
	if path != "" {
		return st.GetByPathOrSlug(ctx, path)
	}
	return nil, errors.New("either id or path is required")
}

func parseInput[T any](raw json.RawMessage, dst *T) error {
	if len(raw) == 0 {
		return nil
	}
	return json.Unmarshal(raw, dst)
}

// --- list_items ---

func listItemsTool(st *store.Store) ToolHandler {
	type input struct {
		ParentPath string   `json:"parent_path"`
		Tags       []string `json:"tags"`
		Management []string `json:"management"`
		Kind       []string `json:"kind"`
		Status     string   `json:"status"`
		Q          string   `json:"q"`
		HasRepo    *bool    `json:"has_repo"`
		HasCalDAV  *bool    `json:"has_caldav"`
		Limit      int      `json:"limit"`
	}
	return func(ctx context.Context, raw json.RawMessage) (any, error) {
		var in input
		if err := parseInput(raw, &in); err != nil {
			return nil, fmt.Errorf("bad params: %w", err)
		}
		items, err := st.ListByFilters(ctx, store.SearchFilters{
			ParentPath: in.ParentPath,
			Tags:       in.Tags,
			Management: in.Management,
			Kind:       in.Kind,
			Status:     in.Status,
			Q:          in.Q,
			HasRepo:    in.HasRepo,
			HasCalDAV:  in.HasCalDAV,
			Limit:      in.Limit,
		})
		if err != nil {
			return nil, err
		}
		views := make([]itemView, 0, len(items))
		for _, it := range items {
			views = append(views, toItemView(it))
		}
		return map[string]any{"items": views, "count": len(views)}, nil
	}
}

// --- get_item ---

func getItemTool(st *store.Store) ToolHandler {
	type input struct {
		ID           string `json:"id"`
		Path         string `json:"path"`
		IncludeLinks *bool  `json:"include_links"`
	}
	return func(ctx context.Context, raw json.RawMessage) (any, error) {
		var in input
		if err := parseInput(raw, &in); err != nil {
			return nil, fmt.Errorf("bad params: %w", err)
		}
		it, err := resolveItem(ctx, st, in.ID, in.Path)
		if err != nil {
			return nil, err
		}
		view := toItemView(it)
		include := true
		if in.IncludeLinks != nil {
			include = *in.IncludeLinks
		}
		if include {
			links, err := st.LinksByType(ctx, it.ID, "") // pass "" → all types
			// LinksByType filters by ref_type — empty would return nothing. So
			// we explicitly list_all by fanning across the known types.
			_ = err
			links = nil
			for _, t := range []string{"caldav-list", "gitea-repo", "mai-project", "mbrian-node", "url", "mai-task"} {
				ll, err := st.LinksByType(ctx, it.ID, t)
				if err != nil {
					continue
				}
				links = append(links, ll...)
			}
			views := make([]linkView, 0, len(links))
			for _, l := range links {
				views = append(views, toLinkView(l))
			}
			view.Links = views
		}
		return view, nil
	}
}

// --- create_item ---

func createItemTool(st *store.Store) ToolHandler {
	type input struct {
		Slug        string         `json:"slug"`
		Title       string         `json:"title"`
		ParentPaths []string       `json:"parent_paths"`
		Kind        []string       `json:"kind"`
		Tags        []string       `json:"tags"`
		Management  []string       `json:"management"`
		ContentMD   string         `json:"content_md"`
		Status      string         `json:"status"`
		Metadata    map[string]any `json:"metadata"`
	}
	return func(ctx context.Context, raw json.RawMessage) (any, error) {
		var in input
		if err := parseInput(raw, &in); err != nil {
			return nil, fmt.Errorf("bad params: %w", err)
		}
		if in.Slug == "" || in.Title == "" {
			return nil, errors.New("slug and title are required")
		}
		parentIDs, err := resolveParentPaths(ctx, st, in.ParentPaths)
		if err != nil {
			return nil, err
		}
		kind := in.Kind
		if len(kind) == 0 {
			kind = []string{"project"}
		}
		it, err := st.Create(ctx, store.CreateInput{
			Kind:       kind,
			Title:      in.Title,
			Slug:       in.Slug,
			ParentIDs:  parentIDs,
			ContentMD:  in.ContentMD,
			Status:     in.Status,
			Tags:       in.Tags,
			Management: in.Management,
			Metadata:   in.Metadata,
		})
		if err != nil {
			return nil, err
		}
		return toItemView(it), nil
	}
}

func resolveParentPaths(ctx context.Context, st *store.Store, paths []string) ([]string, error) {
	out := make([]string, 0, len(paths))
	for _, p := range paths {
		p = strings.TrimSpace(p)
		if p == "" {
			continue
		}
		it, err := st.GetByPathOrSlug(ctx, p)
		if err != nil {
			return nil, fmt.Errorf("parent path %q: %w", p, err)
		}
		out = append(out, it.ID)
	}
	return out, nil
}

// --- update_item ---

func updateItemTool(st *store.Store) ToolHandler {
	type input struct {
		ID          string    `json:"id"`
		Path        string    `json:"path"`
		Title       *string   `json:"title"`
		Slug        *string   `json:"slug"`
		ParentPaths *[]string `json:"parent_paths"`
		ContentMD   *string   `json:"content_md"`
		Status      *string   `json:"status"`
		Pinned      *bool     `json:"pinned"`
		Archived    *bool     `json:"archived"`
		Tags        *[]string `json:"tags"`
		Management  *[]string `json:"management"`
	}
	return func(ctx context.Context, raw json.RawMessage) (any, error) {
		var in input
		if err := parseInput(raw, &in); err != nil {
			return nil, fmt.Errorf("bad params: %w", err)
		}
		it, err := resolveItem(ctx, st, in.ID, in.Path)
		if err != nil {
			return nil, err
		}
		patch := store.UpdateInput{
			Title:      it.Title,
			Slug:       it.Slug,
			ParentIDs:  it.ParentIDs,
			ContentMD:  it.ContentMD,
			Status:     it.Status,
			Pinned:     it.Pinned,
			Archived:   it.Archived,
			Tags:       it.Tags,
			Management: it.Management,
		}
		if in.Title != nil {
			patch.Title = *in.Title
		}
		if in.Slug != nil {
			patch.Slug = *in.Slug
		}
		if in.ContentMD != nil {
			patch.ContentMD = *in.ContentMD
		}
		if in.Status != nil {
			patch.Status = *in.Status
		}
		if in.Pinned != nil {
			patch.Pinned = *in.Pinned
		}
		if in.Archived != nil {
			patch.Archived = *in.Archived
		}
		if in.Tags != nil {
			patch.Tags = *in.Tags
		}
		if in.Management != nil {
			patch.Management = *in.Management
		}
		if in.ParentPaths != nil {
			pids, err := resolveParentPaths(ctx, st, *in.ParentPaths)
			if err != nil {
				return nil, err
			}
			patch.ParentIDs = pids
		}
		updated, err := st.Update(ctx, it.ID, patch)
		if err != nil {
			return nil, err
		}
		return toItemView(updated), nil
	}
}

// --- delete_item ---

func deleteItemTool(st *store.Store) ToolHandler {
	type input struct {
		ID      string `json:"id"`
		Path    string `json:"path"`
		Cascade bool   `json:"cascade"`
	}
	return func(ctx context.Context, raw json.RawMessage) (any, error) {
		var in input
		if err := parseInput(raw, &in); err != nil {
			return nil, fmt.Errorf("bad params: %w", err)
		}
		it, err := resolveItem(ctx, st, in.ID, in.Path)
		if err != nil {
			return nil, err
		}
		if err := st.SoftDeleteCascade(ctx, it.ID, in.Cascade); err != nil {
			return nil, err
		}
		return map[string]any{"deleted": it.ID, "cascade": in.Cascade}, nil
	}
}

// --- list_links ---

func listLinksTool(st *store.Store) ToolHandler {
	type input struct {
		ID      string `json:"id"`
		Path    string `json:"path"`
		RefType string `json:"ref_type"`
	}
	return func(ctx context.Context, raw json.RawMessage) (any, error) {
		var in input
		if err := parseInput(raw, &in); err != nil {
			return nil, fmt.Errorf("bad params: %w", err)
		}
		it, err := resolveItem(ctx, st, in.ID, in.Path)
		if err != nil {
			return nil, err
		}
		var links []*store.ItemLink
		if in.RefType != "" {
			links, err = st.LinksByType(ctx, it.ID, in.RefType)
		} else {
			for _, t := range []string{"caldav-list", "gitea-repo", "mai-project", "mbrian-node", "url", "mai-task"} {
				ll, lerr := st.LinksByType(ctx, it.ID, t)
				if lerr != nil {
					continue
				}
				links = append(links, ll...)
			}
		}
		if err != nil {
			return nil, err
		}
		views := make([]linkView, 0, len(links))
		for _, l := range links {
			views = append(views, toLinkView(l))
		}
		return map[string]any{"links": views, "count": len(views)}, nil
	}
}

// --- add_link / remove_link ---

func addLinkTool(st *store.Store) ToolHandler {
	type input struct {
		ID        string         `json:"id"`
		Path      string         `json:"path"`
		RefType   string         `json:"ref_type"`
		RefID     string         `json:"ref_id"`
		Rel       string         `json:"rel"`
		Note      string         `json:"note"`
		EventDate string         `json:"event_date"`
		Metadata  map[string]any `json:"metadata"`
	}
	return func(ctx context.Context, raw json.RawMessage) (any, error) {
		var in input
		if err := parseInput(raw, &in); err != nil {
			return nil, fmt.Errorf("bad params: %w", err)
		}
		if in.RefType == "" || in.RefID == "" {
			return nil, errors.New("ref_type and ref_id are required")
		}
		it, err := resolveItem(ctx, st, in.ID, in.Path)
		if err != nil {
			return nil, err
		}
		md := in.Metadata
		if md == nil {
			md = map[string]any{}
		}
		var notePtr *string
		if in.Note != "" {
			n := in.Note
			notePtr = &n
		}
		var datePtr *time.Time
		if strings.TrimSpace(in.EventDate) != "" {
			t, err := time.Parse("2006-01-02", strings.TrimSpace(in.EventDate))
			if err != nil {
				return nil, fmt.Errorf("event_date must be YYYY-MM-DD: %w", err)
			}
			datePtr = &t
		}
		link, err := st.AddLinkDated(ctx, it.ID, in.RefType, in.RefID, in.Rel, notePtr, datePtr, md)
		if err != nil {
			return nil, err
		}
		return toLinkView(link), nil
	}
}

func removeLinkTool(st *store.Store) ToolHandler {
	type input struct {
		LinkID string `json:"link_id"`
	}
	return func(ctx context.Context, raw json.RawMessage) (any, error) {
		var in input
		if err := parseInput(raw, &in); err != nil {
			return nil, fmt.Errorf("bad params: %w", err)
		}
		if in.LinkID == "" {
			return nil, errors.New("link_id is required")
		}
		if err := st.DeleteLink(ctx, in.LinkID); err != nil {
			return nil, err
		}
		return map[string]any{"deleted": in.LinkID}, nil
	}
}

// --- search ---

func searchTool(st *store.Store) ToolHandler {
	type input struct {
		Query string `json:"query"`
		Limit int    `json:"limit"`
	}
	return func(ctx context.Context, raw json.RawMessage) (any, error) {
		var in input
		if err := parseInput(raw, &in); err != nil {
			return nil, fmt.Errorf("bad params: %w", err)
		}
		if in.Query == "" {
			return nil, errors.New("query is required")
		}
		items, err := st.Search(ctx, in.Query, in.Limit)
		if err != nil {
			return nil, err
		}
		views := make([]itemView, 0, len(items))
		for _, it := range items {
			views = append(views, toItemView(it))
		}
		return map[string]any{"items": views, "count": len(views), "query": in.Query}, nil
	}
}

// --- tree ---

type treeNode struct {
	Item     itemView    `json:"item"`
	Path     string      `json:"path"` // the path under which this node appears in the tree
	Children []*treeNode `json:"children"`
}

func treeTool(st *store.Store) ToolHandler {
	type input struct {
		RootPath string `json:"root_path"`
		Depth    int    `json:"depth"`
	}
	return func(ctx context.Context, raw json.RawMessage) (any, error) {
		var in input
		if err := parseInput(raw, &in); err != nil {
			return nil, fmt.Errorf("bad params: %w", err)
		}
		items, err := st.ListAll(ctx)
		if err != nil {
			return nil, err
		}
		// Build adjacency by parent id (the same row appears once per parent).
		byID := map[string]*store.Item{}
		childrenByParent := map[string][]*store.Item{}
		var roots []*store.Item
		for _, it := range items {
			byID[it.ID] = it
			if len(it.ParentIDs) == 0 {
				roots = append(roots, it)
				continue
			}
			for _, pid := range it.ParentIDs {
				childrenByParent[pid] = append(childrenByParent[pid], it)
			}
		}
		var build func(it *store.Item, path string, depth int) *treeNode
		build = func(it *store.Item, path string, depth int) *treeNode {
			n := &treeNode{Item: toItemView(it), Path: path}
			if in.Depth > 0 && depth >= in.Depth {
				return n
			}
			for _, c := range childrenByParent[it.ID] {
				n.Children = append(n.Children, build(c, path+"."+c.Slug, depth+1))
			}
			return n
		}
		var out []*treeNode
		if in.RootPath != "" {
			root, err := st.GetByPathOrSlug(ctx, in.RootPath)
			if err != nil {
				return nil, err
			}
			out = append(out, build(root, in.RootPath, 0))
		} else {
			for _, r := range roots {
				out = append(out, build(r, r.Slug, 0))
			}
		}
		return map[string]any{"tree": out, "roots": len(out)}, nil
	}
}