package catalogue

import (
	"bytes"
	"encoding/json"
	"fmt"
	"math"
	"regexp"
	"sort"
	"strings"
	"text/template"
)

// A kind a seat receives as data, rendered by its holder (novox/hq ADR 0255).
//
// ADR 0212 made a contribution text in the tool's own grammar, which the controller places and never
// reads. That is right where the tool is the seat's for good — a hotkey daemon's trigger lines — and
// wrong where the seat's whole point is that its tool can be replaced: a module adding a battery to the
// bar would write i3status-rust's TOML, and a second bar would have to read it. So a seat may define a
// kind as data instead. The seat says the data's shape; a contributor gives data in that shape; the
// holder gives a template that renders one piece of it into its tool's grammar, as a module's facts
// template renders the roster (`facts`): the data is the mesh's, the format is the holder's.
//
// What the holder places is narrowed by the shape's placing fields — the bar's `bar` and `place` — in
// the placeholder, `${contribution:<seat>:<kind>:<field>=<value>,…}`, and every combination of them is
// placed by the holder exactly once, so nothing a module contributes is dropped by a holder that forgot
// a corner of the shape.

// Shape is what a kind received as data looks like.
type Shape struct {
	// Places are the fields a holder narrows its placeholders by, each with every value it takes.
	Places []PlaceField
	// Order is the whole-number field that orders the pieces within one placeholder (lowest first,
	// then module order); absent in a piece means OrderDefault.
	Order string
	// Check is what else is wrong with one piece's data, beyond its placing fields and its order.
	Check func(data map[string]any) []string `json:"-"`
	// Examples are pieces every holder's template must render, one for each variant the shape has,
	// so a holder that cannot render one is refused at registration and not found on a machine.
	Examples []map[string]any
}

// PlaceField is one field a holder places by, and the values it takes.
type PlaceField struct {
	Field  string
	Values []string
}

// OrderDefault is a piece's order when it gives none: the middle of 0–99.
const OrderDefault = 50

// capabilityName is the shape of a capability's name, as a node's profile reports it.
var capabilityName = regexp.MustCompile(`^[a-z0-9][a-z0-9-]*$`)

// KnownCapabilities is every capability the node-engine detects (mesh-host internal/profile), the
// names an `if-capability` may give (novox/hq ADR 0255). A name nothing detects would leave its
// contribution out on every machine, silently, so it is refused. A detector added there is added here.
var KnownCapabilities = []string{
	"battery", "container-runtime", "firewall", "graphical-session", "overlay", "package-manager",
	"power-meter", "privileged", "seat", "service-manager", "uplink-dhcpcd", "uplink-networkmanager",
	"uplink-systemd-networkd", "virtualisation",
}

// renderFuncs are the functions a holder's template may call. `quote` writes a value as a JSON
// string with DEL escaped as well — JSON leaves it bare, and TOML refuses it — which makes it a valid
// basic string in TOML and in most tools' grammars, so a contributed command with quotes or control
// characters in it cannot break out of the holder's line.
var renderFuncs = template.FuncMap{"quote": quote}

func quote(v any) (string, error) {
	b, err := json.Marshal(fmt.Sprint(v))
	return strings.ReplaceAll(string(b), "\x7f", `\u007f`), err
}

// shapedProblems is what is wrong with one contribution of a kind received as data.
func shapedProblems(module string, i int, r Receivable, c SeatContribution) []string {
	var problems []string
	at := fmt.Sprintf("%s's contribution %d to %s (%s)", module, i+1, c.Seat, c.Kind)
	if strings.TrimSpace(c.Content) != "" {
		problems = append(problems, at+" has content; this kind is data, given as `data` (novox/hq ADR 0255)")
	}
	if len(c.Data) == 0 {
		return append(problems, at+" has no data")
	}
	for _, p := range r.Shape.Places {
		v, _ := c.Data[p.Field].(string)
		if !oneOf(p.Values, v) {
			problems = append(problems, fmt.Sprintf("%s says %s %q; it is one of %s",
				at, p.Field, fmt.Sprint(c.Data[p.Field]), strings.Join(p.Values, ", ")))
		}
	}
	if r.Shape.Order != "" {
		if v, has := c.Data[r.Shape.Order]; has {
			if _, ok := wholeIn(v, 0, 99); !ok {
				problems = append(problems, fmt.Sprintf("%s says %s %v; it is a whole number from 0 to 99",
					at, r.Shape.Order, v))
			}
		}
	}
	if r.Shape.Check != nil {
		for _, p := range r.Shape.Check(c.Data) {
			problems = append(problems, at+": "+p)
		}
	}
	return problems
}

// wholeIn is v as a whole number within [lo, hi]; JSON gives every number as a float.
func wholeIn(v any, lo, hi int) (int, bool) {
	f, ok := v.(float64)
	if !ok {
		if i, isInt := v.(int); isInt {
			f, ok = float64(i), true
		}
	}
	if !ok || f != math.Trunc(f) || f < float64(lo) || f > float64(hi) {
		return 0, false
	}
	return int(f), true
}

// placeholderWhere parses the narrowing part of a placeholder, `bar=bottom,place=status`, against the
// kind's shape. Empty narrows nothing.
func placeholderWhere(r Receivable, where string) (map[string]string, error) {
	out := map[string]string{}
	if where == "" {
		return out, nil
	}
	if r.Shape == nil {
		return nil, fmt.Errorf("%s is text, which a placeholder does not narrow", r.Kind)
	}
	for _, pair := range strings.Split(where, ",") {
		field, value, ok := strings.Cut(pair, "=")
		var p *PlaceField
		for i := range r.Shape.Places {
			if r.Shape.Places[i].Field == field {
				p = &r.Shape.Places[i]
			}
		}
		switch {
		case !ok || p == nil:
			return nil, fmt.Errorf("%q narrows by %s, and %s is placed by %s", where, field, r.Kind, placeFields(r))
		case !oneOf(p.Values, value):
			return nil, fmt.Errorf("%q says %s=%s; %s is one of %s", where, field, value, field, strings.Join(p.Values, ", "))
		case out[field] != "":
			return nil, fmt.Errorf("%q names %s twice", where, field)
		}
		out[field] = value
	}
	return out, nil
}

func placeFields(r Receivable) string {
	var names []string
	for _, p := range r.Shape.Places {
		names = append(names, p.Field)
	}
	return strings.Join(names, ", ")
}

// holderTemplate is the holder's template for a kind, parsed.
func holderTemplate(holder Manifest, seat Seat, kind string) (*template.Template, error) {
	for _, c := range holder.Claims {
		if s, known := SeatNamed(c.Name); !known || s.Name != seat.Name {
			continue
		}
		text, has := c.Renders[kind]
		if !has || strings.TrimSpace(text) == "" {
			break
		}
		t, err := template.New(seat.Name + ":" + kind).Funcs(renderFuncs).Parse(text)
		if err != nil {
			return nil, fmt.Errorf("%s's template for %s:%s does not parse: %v", holder.Module, seat.Name, kind, err)
		}
		return t, nil
	}
	return nil, fmt.Errorf("%s places %s:%s, which is data, and its claim gives no template for it in `renders` "+
		"(novox/hq ADR 0255)", holder.Module, seat.Name, kind)
}

// renderPiece is one piece of data in the holder's grammar. The template sees the piece's fields and
// `module`, the contributor. A value the piece does not have reads as nothing in a `with` or an `if`;
// printed bare it would write `<no value>` into the tool's file, which is refused here instead.
func renderPiece(t *template.Template, module string, data map[string]any) (string, error) {
	view := map[string]any{"module": module}
	for k, v := range data {
		view[k] = v
	}
	var b bytes.Buffer
	if err := t.Execute(&b, view); err != nil {
		return "", fmt.Errorf("rendering %s's piece: %v", module, err)
	}
	out := b.String()
	if strings.Contains(out, "<no value>") {
		return "", fmt.Errorf("rendering %s's piece printed a value it does not have: %q", module, out)
	}
	return out, nil
}

// placedPiece is one contributed piece on its way into a holder's file.
type placedPiece struct {
	module string
	data   map[string]any
	order  int
}

// shapedContributions is every module's data of one kind to one seat, narrowed by where and by the
// machine's capabilities, ordered, and rendered through the holder's template — each piece under a
// comment line naming its module.
//
// A piece the template renders to nothing — a `shows` the holder does not know yet — or fails on is
// left out and answered as unplaced, naming its module: the other pieces and the rest of the machine's
// declaration go on (novox/hq ADR 0255).
func shapedContributions(modules []Manifest, holder Manifest, s Seat, r Receivable, where map[string]string, caps map[string]bool) (string, []string, error) {
	var pieces []placedPiece
	for _, m := range inModuleOrder(modules) {
		for _, c := range m.allContributions() {
			if c.Kind != r.Kind || !capable(c, caps) {
				continue
			}
			if cs, known := SeatNamed(c.Seat); !known || cs.Name != s.Name {
				continue
			}
			match := true
			for field, value := range where {
				if v, _ := c.Data[field].(string); v != value {
					match = false
				}
			}
			if !match {
				continue
			}
			order := OrderDefault
			if v, ok := wholeIn(c.Data[r.Shape.Order], 0, 99); ok {
				order = v
			}
			pieces = append(pieces, placedPiece{module: m.Module, data: c.Data, order: order})
		}
	}
	if len(pieces) == 0 {
		return "", nil, nil
	}
	t, err := holderTemplate(holder, s, r.Kind)
	if err != nil {
		return "", nil, err
	}
	sort.SliceStable(pieces, func(a, b int) bool { return pieces[a].order < pieces[b].order })
	var b strings.Builder
	var unplaced []string
	for _, p := range pieces {
		out, err := renderPiece(t, p.module, p.data)
		if err == nil && strings.TrimSpace(out) == "" {
			err = fmt.Errorf("%s's template renders nothing for it", holder.Module)
		}
		if err != nil {
			unplaced = append(unplaced, fmt.Sprintf("%s's %s:%s %s is not placed by %s: %v",
				p.module, s.Name, r.Kind, describePiece(p.data), holder.Module, err))
			continue
		}
		fmt.Fprintf(&b, "%s %s\n", r.Comment, p.module)
		b.WriteString(out)
		if !strings.HasSuffix(out, "\n") {
			b.WriteString("\n")
		}
	}
	return b.String(), unplaced, nil
}

// describePiece is a piece in one line, its fields in order, for a person reading why it was left out.
func describePiece(data map[string]any) string {
	var parts []string
	for _, k := range sortedKeys(data) {
		if _, nested := data[k].(map[string]any); nested {
			continue
		}
		parts = append(parts, fmt.Sprintf("%s=%v", k, data[k]))
	}
	return "(" + strings.Join(parts, " ") + ")"
}

// capable is whether a contribution applies on a machine with these capabilities: always, unless it
// names one with `if-capability` the machine did not report (novox/hq ADR 0255). A machine whose
// capabilities are not known has none, so a conditional piece is left out rather than guessed in.
func capable(c SeatContribution, caps map[string]bool) bool {
	return c.IfCapability == "" || caps[c.IfCapability]
}

// placementProblems is what is wrong with how a holder places the kinds its seats receive as data:
// once it places one at all, it needs a template that renders every example of the shape, and every combination of the placing
// fields placed exactly once across its files — or something contributed would be dropped, or written
// twice (novox/hq ADR 0255).
func (m Manifest) placementProblems() []string {
	var problems []string
	for _, c := range m.Claims {
		s, known := SeatNamed(c.Name)
		if !known {
			continue
		}
		for _, r := range s.Receives {
			// A holder that places none of the kind is older than it (novox/hq ADR 0255): refusing it
			// would refuse every bar registered before the kind existed, and the controller that
			// defines the kind ships first. Its contributions wait, unplaced, until it places them.
			if r.Shape == nil || !placesKind(m, s, r.Kind) {
				continue
			}
			t, err := holderTemplate(m, s, r.Kind)
			if err != nil {
				problems = append(problems, err.Error())
				continue
			}
			for _, ex := range r.Shape.Examples {
				if out, err := renderPiece(t, "example", ex); err != nil || strings.TrimSpace(out) == "" {
					problems = append(problems, fmt.Sprintf("%s's template for %s:%s renders nothing for %v: %v",
						m.Module, s.Name, r.Kind, ex, err))
				}
			}
			placed := map[string]int{}
			for _, res := range m.Resources {
				content, _ := res["content"].(string)
				for _, f := range ofContribution.FindAllStringSubmatch(content, -1) {
					seat, rest, _ := strings.Cut(f[1], ":")
					kind, whereText, _ := strings.Cut(rest, ":")
					if cs, ok := SeatNamed(seat); !ok || cs.Name != s.Name || kind != r.Kind {
						continue
					}
					where, err := placeholderWhere(r, whereText)
					if err != nil {
						continue // said by seatPlaceholderProblems
					}
					for _, combo := range combinations(r.Shape.Places) {
						if covers(where, combo) {
							placed[comboKey(combo)]++
						}
					}
				}
			}
			for _, combo := range combinations(r.Shape.Places) {
				switch n := placed[comboKey(combo)]; {
				case n == 0:
					problems = append(problems, fmt.Sprintf("%s never places %s:%s for %s; every combination of %s is "+
						"placed once, or a contribution to it is lost (novox/hq ADR 0255)",
						m.Module, s.Name, r.Kind, comboKey(combo), placeFields(r)))
				case n > 1:
					problems = append(problems, fmt.Sprintf("%s places %s:%s for %s %d times; once, or a contribution "+
						"is written twice (novox/hq ADR 0255)", m.Module, s.Name, r.Kind, comboKey(combo), n))
				}
			}
		}
	}
	return problems
}

// placesKind is whether any of a holder's files names the kind's placeholder.
func placesKind(m Manifest, s Seat, kind string) bool {
	for _, res := range m.Resources {
		content, _ := res["content"].(string)
		for _, f := range ofContribution.FindAllStringSubmatch(content, -1) {
			seat, rest, _ := strings.Cut(f[1], ":")
			k, _, _ := strings.Cut(rest, ":")
			if cs, ok := SeatNamed(seat); ok && cs.Name == s.Name && k == kind {
				return true
			}
		}
	}
	return false
}

// combinations is every assignment of a value to each placing field.
func combinations(places []PlaceField) []map[string]string {
	out := []map[string]string{{}}
	for _, p := range places {
		var next []map[string]string
		for _, partial := range out {
			for _, v := range p.Values {
				c := map[string]string{p.Field: v}
				for k, w := range partial {
					c[k] = w
				}
				next = append(next, c)
			}
		}
		out = next
	}
	return out
}

func covers(where, combo map[string]string) bool {
	for field, value := range where {
		if combo[field] != value {
			return false
		}
	}
	return true
}

func comboKey(combo map[string]string) string {
	var parts []string
	for _, k := range sortedKeys(combo) {
		parts = append(parts, k+"="+combo[k])
	}
	return strings.Join(parts, ",")
}