// Package assistant answers questions about a shop in plain language, by
// calling the same business questions the screens ask.
//
// The tools here are deliberately BUSINESS-level - `store_footfall`, not
// `execute_sql`. That is not a stylistic preference. An assistant handed raw
// SQL has to invent the arithmetic, and this product's arithmetic is full of
// traps that produce a plausible wrong number rather than an error:
//
//   - unique visitors is not the sum of the daily bars
//   - "new" means first-ever, not first-in-this-window
//   - new + returning can be less than the total, because a site sending
//     counts without templates records real people nobody identified
//   - revenue is one currency; adding rupees to dollars produces something
//     that looks like money and is not
//
// Every one of those is already settled, tested, and used by the reports. A
// tool that returns the settled answer cannot get them wrong; a tool that
// returns rows invites the model to re-derive them badly.
//
// The same registry is what an MCP server would expose. Nothing here depends
// on the Anthropic SDK - that lives in one file next door - so a second
// consumer needs no changes.
package assistant

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

	"github.com/loyaly/behavision-server/internal/api"
	"github.com/loyaly/behavision-server/internal/auth"
)

// Store is what the assistant needs. A narrow interface, and read-mostly on
// purpose: the one thing it can change is asking a shop PC to check a camera,
// which is reversible and is the single action a support conversation actually
// needs to take.
type Store interface {
	SiteHealth(ctx context.Context, clientID string) ([]api.SiteHealth, error)
	Cameras(ctx context.Context, clientID, siteID string) ([]api.Camera, error)
	CameraByID(ctx context.Context, clientID, id string) (api.Camera, error)
	RequestCheck(ctx context.Context, clientID, id, kind string, seconds int) error
	Footfall(ctx context.Context, q api.ReportQuery) ([]api.FootfallPoint, api.Totals, error)
	Conversion(ctx context.Context, q api.ReportQuery) (api.SalesReport, error)
	SearchVisitors(ctx context.Context, clientID, query string, limit int) ([]api.Customer, error)
}

// Tool is one business question, independent of any LLM SDK.
type Tool struct {
	Name        string
	Description string
	// Schema is a JSON Schema object for the arguments.
	Schema map[string]any
	// Run answers it. The principal is the SIGNED-IN USER, passed in by the
	// caller and never taken from the arguments - see Registry.Call.
	Run func(ctx context.Context, p auth.Principal, args json.RawMessage) (any, error)
}

type Registry struct {
	Store Store
	// SiteChecker is the smoke test. A func rather than a method so the
	// judgement stays in the api package beside the screens that show it.
	SiteChecker func(site *api.SiteHealth, cams []api.Camera, now time.Time) []api.CheckStep
	Now         func() time.Time
	tools       []Tool
}

func (r *Registry) now() time.Time {
	if r.Now != nil {
		return r.Now()
	}
	return time.Now().UTC()
}

// Call runs a tool as a specific signed-in user.
//
// The principal comes from the SESSION and is passed in here; no tool takes a
// client_id argument, so there is nothing for the model to set. That is the
// whole tenancy story for the assistant, and it is a property of the
// signatures rather than of anybody remembering to check.
func (r *Registry) Call(ctx context.Context, p auth.Principal, name string,
	args json.RawMessage) (string, error) {

	for _, t := range r.Tools() {
		if t.Name != name {
			continue
		}
		out, err := t.Run(ctx, p, args)
		if err != nil {
			// Returned as a RESULT, not an error: the model can usually
			// recover ("that shop does not exist - here are the ones that
			// do"), and killing the turn would leave the user with nothing.
			return fmt.Sprintf("That did not work: %v", err), nil
		}
		body, err := json.Marshal(out)
		if err != nil {
			return "", err
		}
		return string(body), nil
	}
	return "", fmt.Errorf("no such tool %q", name)
}

func (r *Registry) Tools() []Tool {
	if r.tools == nil {
		r.tools = r.build()
	}
	return r.tools
}

func obj(props map[string]any, required ...string) map[string]any {
	if required == nil {
		required = []string{}
	}
	return map[string]any{
		"type": "object", "properties": props,
		"required": required, "additionalProperties": false,
	}
}

func str(desc string) map[string]any { return map[string]any{"type": "string", "description": desc} }

func (r *Registry) build() []Tool {
	return []Tool{
		{
			Name: "list_shops",
			Description: "Every shop this account can see, with whether its PC is online, " +
				"how many cameras are connected, and what share of the faces its cameras " +
				"saw were too poor to recognise. Start here when a question names a shop.",
			Schema: obj(map[string]any{}),
			Run: func(ctx context.Context, p auth.Principal, _ json.RawMessage) (any, error) {
				return r.Store.SiteHealth(ctx, p.ClientID)
			},
		},
		{
			Name: "check_shop",
			Description: "Run the end-to-end check on one shop: is the PC online, is " +
				"recognition running, are cameras connected, can they recognise faces, " +
				"are visits reaching head office. Use this for 'is X working' and for " +
				"any complaint that footfall looks wrong or too low.",
			Schema: obj(map[string]any{"shop": str("The shop's name or id")}, "shop"),
			Run: func(ctx context.Context, p auth.Principal, raw json.RawMessage) (any, error) {
				var in struct {
					Shop string `json:"shop"`
				}
				if err := json.Unmarshal(raw, &in); err != nil {
					return nil, err
				}
				site, err := r.findSite(ctx, p, in.Shop)
				if err != nil {
					return nil, err
				}
				cams, err := r.Store.Cameras(ctx, p.ClientID, site.SiteID)
				if err != nil {
					return nil, err
				}
				return map[string]any{
					"shop":  site.Name,
					"steps": r.SiteChecker(site, cams, r.now()),
				}, nil
			},
		},
		{
			Name: "list_cameras",
			Description: "Cameras, with whether each is connected and whether anyone has " +
				"proved it can actually recognise a face. Those are different things: a " +
				"camera can stream perfectly and still produce views nothing can recognise.",
			Schema: obj(map[string]any{"shop": str("Optional: limit to one shop")}),
			Run: func(ctx context.Context, p auth.Principal, raw json.RawMessage) (any, error) {
				var in struct {
					Shop string `json:"shop"`
				}
				_ = json.Unmarshal(raw, &in)
				siteID := ""
				if strings.TrimSpace(in.Shop) != "" {
					site, err := r.findSite(ctx, p, in.Shop)
					if err != nil {
						return nil, err
					}
					siteID = site.SiteID
				}
				cams, err := r.Store.Cameras(ctx, p.ClientID, siteID)
				if err != nil {
					return nil, err
				}
				// Trimmed deliberately. The full row carries object keys and
				// connection details that are of no use in an answer and would
				// spend context on every turn.
				out := make([]map[string]any, 0, len(cams))
				for _, c := range cams {
					out = append(out, map[string]any{
						"id": c.ID, "name": c.Label, "shop": c.Site,
						"connected": c.Connected,
						"verified":  verificationOf(c),
					})
				}
				return out, nil
			},
		},
		{
			Name: "check_camera",
			Description: "Ask a shop's PC to test one camera. kind=connection asks whether " +
				"it can open the stream; kind=placement watches for 25 seconds and judges " +
				"whether somebody walking past produces a view good enough to recognise - " +
				"that one needs a person to actually walk past. The answer arrives in a " +
				"couple of minutes, not immediately.",
			Schema: obj(map[string]any{
				"camera_id": str("The camera's id, from list_cameras"),
				"kind":      map[string]any{"type": "string", "enum": []string{"connection", "placement"}},
			}, "camera_id", "kind"),
			Run: func(ctx context.Context, p auth.Principal, raw json.RawMessage) (any, error) {
				var in struct {
					CameraID string `json:"camera_id"`
					Kind     string `json:"kind"`
				}
				if err := json.Unmarshal(raw, &in); err != nil {
					return nil, err
				}
				if !p.CanManageSites() {
					// Refused here rather than left to the prompt. An
					// instruction not to do something is not a permission
					// check, and this one writes to a shop's PC.
					return nil, fmt.Errorf(
						"this account cannot run camera checks - a manager or owner can")
				}
				if in.Kind != "connection" && in.Kind != "placement" {
					return nil, fmt.Errorf(`kind must be "connection" or "placement"`)
				}
				if err := r.Store.RequestCheck(ctx, p.ClientID, in.CameraID, in.Kind, 25); err != nil {
					return nil, fmt.Errorf("no camera with that id")
				}
				cam, err := r.Store.CameraByID(ctx, p.ClientID, in.CameraID)
				if err != nil {
					return nil, err
				}
				return map[string]any{
					"requested": in.Kind, "camera": cam.Label, "shop": cam.Site,
					"note": "The shop's PC picks this up within a couple of minutes. " +
						"Tell the person to watch the camera's card for the result.",
				}, nil
			},
		},
		{
			Name: "footfall",
			Description: "How many people visited. Returns unique people over the window " +
				"AND the visit count, which are different numbers - a regular is one " +
				"person and several visits. Also returns what share of faces were too " +
				"poor to recognise, which says whether the figure can be believed at all.",
			Schema: obj(map[string]any{
				"from": str("YYYY-MM-DD"), "to": str("YYYY-MM-DD (inclusive)"),
				"shop":   str("Optional: one shop"),
				"bucket": map[string]any{"type": "string", "enum": []string{"hour", "day", "week", "month"}},
			}, "from", "to"),
			Run: func(ctx context.Context, p auth.Principal, raw json.RawMessage) (any, error) {
				q, err := r.reportQuery(ctx, p, raw)
				if err != nil {
					return nil, err
				}
				points, totals, err := r.Store.Footfall(ctx, q)
				if err != nil {
					return nil, err
				}
				return map[string]any{
					"unique_people": totals.UniqueVisitors,
					"visits":        totals.Visits,
					"per_bucket":    points,
					"timezone":      q.Timezone,
					"fraction_of_faces_too_poor_to_recognise": totals.FractionBelowGate,
					"worst_shop":                              totals.WorstSite,
					"note": "unique_people is people; visits counts every appearance. " +
						"They differ because regulars come back - do not add the buckets up " +
						"to get unique_people.",
				}, nil
			},
		},
		{
			Name: "sales",
			Description: "How many visitors bought something, the conversion rate, revenue " +
				"and average basket. Revenue is a single currency - whichever accounts for " +
				"most of it - and average basket is per basket, not per person.",
			Schema: obj(map[string]any{
				"from": str("YYYY-MM-DD"), "to": str("YYYY-MM-DD (inclusive)"),
				"shop": str("Optional: one shop"),
			}, "from", "to"),
			Run: func(ctx context.Context, p auth.Principal, raw json.RawMessage) (any, error) {
				q, err := r.reportQuery(ctx, p, raw)
				if err != nil {
					return nil, err
				}
				return r.Store.Conversion(ctx, q)
			},
		},
		{
			Name: "find_customer",
			Description: "Search customers by name, phone or email. Returns how many times " +
				"each has visited and whether they have given consent for their details to " +
				"be kept.",
			Schema: obj(map[string]any{"query": str("Part of a name, phone or email")}, "query"),
			Run: func(ctx context.Context, p auth.Principal, raw json.RawMessage) (any, error) {
				var in struct {
					Query string `json:"query"`
				}
				if err := json.Unmarshal(raw, &in); err != nil {
					return nil, err
				}
				return r.Store.SearchVisitors(ctx, p.ClientID, in.Query, 10)
			},
		},
	}
}

// findSite resolves what a person typed to a shop they can see.
//
// Matched against the tenant's OWN shops, so a name the model invented or a
// caller supplied cannot reach another tenant: the candidate list never
// contains anybody else's shops in the first place.
func (r *Registry) findSite(ctx context.Context, p auth.Principal, want string) (*api.SiteHealth, error) {
	sites, err := r.Store.SiteHealth(ctx, p.ClientID)
	if err != nil {
		return nil, err
	}
	want = strings.ToLower(strings.TrimSpace(want))
	if want == "" && len(sites) == 1 {
		// One shop and no name given: the question can only be about that one.
		return &sites[0], nil
	}
	for i := range sites {
		if strings.EqualFold(sites[i].SiteID, want) ||
			strings.EqualFold(sites[i].Slug, want) ||
			strings.Contains(strings.ToLower(sites[i].Name), want) {
			return &sites[i], nil
		}
	}
	names := make([]string, 0, len(sites))
	for _, s := range sites {
		names = append(names, s.Name)
	}
	return nil, fmt.Errorf("no shop matching %q. This account has: %s",
		want, strings.Join(names, ", "))
}

func (r *Registry) reportQuery(ctx context.Context, p auth.Principal,
	raw json.RawMessage) (api.ReportQuery, error) {

	var in struct {
		From, To, Shop, Bucket string
	}
	if err := json.Unmarshal(raw, &in); err != nil {
		return api.ReportQuery{}, err
	}
	q := api.ReportQuery{ClientID: p.ClientID, Bucket: in.Bucket, Timezone: "Asia/Kolkata"}
	if q.Bucket == "" {
		q.Bucket = "day"
	}
	from, err := time.Parse("2006-01-02", in.From)
	if err != nil {
		return q, fmt.Errorf("from must be a date like 2026-09-01")
	}
	to, err := time.Parse("2006-01-02", in.To)
	if err != nil {
		return q, fmt.Errorf("to must be a date like 2026-09-02")
	}
	// `to` is inclusive to a person and exclusive in SQL. Converted here, in
	// one place, exactly as the report handler does - otherwise a question
	// about "the 1st to the 7th" quietly loses the 7th's trade.
	q.From, q.To = from, to.AddDate(0, 0, 1)
	if !q.To.After(q.From) {
		return q, fmt.Errorf("to must be on or after from")
	}
	if strings.TrimSpace(in.Shop) != "" {
		site, err := r.findSite(ctx, p, in.Shop)
		if err != nil {
			return q, err
		}
		q.SiteID = site.SiteID
	}
	return q, nil
}

// verificationOf is the same two-claim distinction the camera card makes.
func verificationOf(c api.Camera) string {
	switch {
	case c.Check.State != "done":
		return "never checked"
	case c.Check.Kind == "placement" && c.Check.OK:
		return "proved it can recognise faces"
	case c.Check.Kind == "placement":
		return "checked and CANNOT recognise faces here: " + c.Check.Headline
	case c.Check.OK:
		return "stream works, but nobody has proved it can recognise a face"
	default:
		return "could not be reached: " + c.Check.Headline
	}
}