package resolution

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

	mcat "git.novox.be/novox/mesh-sdk/go/catalogue"
)

// collectableAsText is whether a collector may name a kind received as data as a collection.
func collectableAsText(r mcat.Receivable) bool { return r.Shape != nil && r.Shape.Text }

// 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
}

// 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 mcat.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 *mcat.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 mcat.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 mcat.Manifest, seat mcat.Seat, kind string) (*template.Template, error) {
	for _, c := range holder.Claims {
		if s, known := mcat.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,
// `module`, the contributor, and `machine`, the node it is composed for. 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, machine string, data map[string]any) (string, error) {
	view := map[string]any{"module": module, "machine": machine}
	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
	// text is a moved contributor's item, rendered (collections.go heldItems): placed as it is, not through the
	// holder's template.
	text string
	item bool
}

// 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 []mcat.Manifest, holder mcat.Manifest, machine string, facts map[string]string, s mcat.Seat, r mcat.Receivable, where map[string]string, caps map[string]bool) (string, []string, error) {
	var pieces []placedPiece
	for _, m := range inModuleOrder(modules) {
		for _, c := range manifestAllContributions(m) {
			if c.Kind != r.Kind || !capable(c, caps) {
				continue
			}
			if cs, known := mcat.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 := mcat.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})
		}
		// A moved contributor's items of the kind, by their attributes (design 57 L3, issue 777): each in its
		// module's place, by its order, then its name.
		if !r.Dirs {
			for _, h := range heldItems(m, "contribution:"+s.Name+":"+r.Kind, where, facts, caps) {
				pieces = append(pieces, placedPiece{module: m.Module, order: itemOrder(h.item), text: h.text, item: true})
			}
		}
	}
	if len(pieces) == 0 {
		return "", nil, nil
	}
	var t *template.Template
	for _, p := range pieces {
		if p.item {
			continue
		}
		var err error
		if t, err = holderTemplate(holder, s, r.Kind); err != nil {
			return "", nil, err
		}
		break
	}
	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 {
		if p.item {
			fmt.Fprintf(&b, "%s %s\n", r.Comment, p.module)
			b.WriteString(p.text)
			continue
		}
		out, err := renderPiece(t, p.module, machine, 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 mcat.SeatContribution, caps map[string]bool) bool {
	return c.IfCapability == "" || caps[c.IfCapability]
}