package resolution

import (
	"fmt"
	"regexp"
	"slices"
	"sort"
	"strconv"
	"strings"

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

func itemKey(it mcat.Item) string { return mcat.ItemKey(it.Collection, it.Name) }

// order is the item's place among the items of one placeholder: its `order` attribute, or OrderDefault.
func itemOrder(it mcat.Item) int {
	if n, err := strconv.Atoi(it.Attributes[mcat.OrderAttribute]); err == nil && n >= 0 && n <= 99 {
		return n
	}
	return mcat.OrderDefault
}

// matches is whether the item's attributes carry every pair of the selector.
func itemMatches(it mcat.Item, where map[string]string) bool {
	for k, v := range where {
		if got, has := it.Attributes[k]; !has || got != v {
			return false
		}
	}
	return true
}

// itemsInOrder is the module's items by order, then name; the order the old form placed a module's pieces in.
func itemsInOrder(items []mcat.Item) []mcat.Item {
	out := append([]mcat.Item(nil), items...)
	sort.SliceStable(out, func(a, b int) bool {
		if oa, ob := itemOrder(out[a]), itemOrder(out[b]); oa != ob {
			return oa < ob
		}
		return out[a].Name < out[b].Name
	})
	return out
}

// oldCollectionNamespaces are the namespaces read as collections of their own name.
var oldCollectionNamespaces = []string{"shell", "environment", "contribution"}

// ofCollected is where a collector places a collection. Loose inside the braces, so a misspelt name is refused.
var ofCollected = regexp.MustCompile(`\$\{collected:([^}]*)\}`)

var attributeKey = regexp.MustCompile(`^[a-z][a-z0-9-]*$`)

var attributeValue = regexp.MustCompile(`^[a-z0-9][a-z0-9_.-]*$`)

// splitSelector is a placeholder's name without its selector, and the selector: `widgets:bar=top,place=left` is
// `widgets` and `bar=top,place=left`. A collection's name holds no `=`, so the selector begins at the last colon
// before the first one.
func splitSelector(name string) (collection, selector string) {
	eq := strings.Index(name, "=")
	if eq < 0 {
		return name, ""
	}
	colon := strings.LastIndex(name[:eq], ":")
	if colon < 0 {
		return name, ""
	}
	return name[:colon], name[colon+1:]
}

// selectorOf is a selector's pairs, or why it is none.
func selectorOf(selector string) (map[string]string, error) {
	out := map[string]string{}
	if selector == "" {
		return out, nil
	}
	for _, pair := range strings.Split(selector, ",") {
		k, v, ok := strings.Cut(pair, "=")
		switch {
		case !ok || !attributeKey.MatchString(k) || !attributeValue.MatchString(v):
			return nil, fmt.Errorf("%q in %q is not <attribute>=<value>", pair, selector)
		case out[k] != "":
			return nil, fmt.Errorf("%q names %s twice", selector, k)
		}
		out[k] = v
	}
	return out, nil
}

// collectionOfPlaceholder is the collection a placeholder's namespace and key name, and whether they name one.
func collectionOfPlaceholder(namespace, key string) (string, bool) {
	key, _ = splitSelector(key)
	switch {
	case namespace == mcat.CollectedNamespace && strings.HasPrefix(key, mcat.EnvironmentCollection+":"):
		// The environment is one collection, and the rest of the name picks the rendering (issue 795).
		return mcat.EnvironmentCollection, true
	case namespace == mcat.CollectedNamespace:
		return key, true
	case namespace == "environment":
		return mcat.EnvironmentCollection, true
	case slices.Contains(oldCollectionNamespaces, namespace):
		return namespace + ":" + key, true
	}
	return "", false
}

// oldCollection is an old namespace's collection by its name: its comment, or why no item may be contributed to it.
// ok is false for a name that is not an old namespace's.
//
// forItem is whether an item is to be contributed to it: an item may be contributed to a kind received as data,
// which a collector may place as a collection only where its shape says its pieces are text (design 57 L3).
func oldCollection(name string, forItem bool) (comment string, old bool, wrong error) {
	namespace, key, _ := strings.Cut(name, ":")
	if !slices.Contains(oldCollectionNamespaces, namespace) {
		return "", false, nil
	}
	switch namespace {
	case "shell":
		target, slot, two := strings.Cut(key, ":")
		if !two || !oneOf(contributionTargets(), target) || !oneOf(knownSlots, slot) {
			return "", true, fmt.Errorf("%s is no slot: shell code is shell:<shell>:<slot>, the shell one of %s, "+
				"the session's file one of %s or the power moment one of %s, and the slot one of %s", name,
				strings.Join(knownShells, ", "), strings.Join(sessionFiles, ", "), strings.Join(powerMoments, ", "),
				strings.Join(knownSlots, ", "))
		}
		// shellCode's line before each module's code.
		return "#", true, nil
	case "environment":
		if key == "" {
			// The collection itself, which an item is contributed to; a placeholder names a rendering.
			return "#", true, nil
		}
		if key != mcat.EnvironmentPOSIX && key != mcat.EnvironmentSystemd {
			return "", true, fmt.Errorf("%s is no format: the environment is environment:%s or environment:%s",
				name, mcat.EnvironmentPOSIX, mcat.EnvironmentSystemd)
		}
		return "#", true, nil
	}
	seat, kind, _ := strings.Cut(key, ":")
	s, r, ok := receivable(seat, kind)
	switch {
	case !ok && s.Name == "":
		return "", true, fmt.Errorf("%s names the seat %q, which the mesh does not define", name, seat)
	case !ok:
		return "", true, fmt.Errorf("%s: %s; %s", name, s.Name, kindsOf(s))
	case r.Shape != nil && (forItem || collectableAsText(r)):
		return r.Comment, true, nil
	case r.Shape != nil:
		return "", true, fmt.Errorf("%s is received by %s as data in its own shape, which no item of text is "+
			"(novox/hq ADR 0255)", name, s.Name)
	case r.Dirs:
		return "", true, fmt.Errorf("%s names its contributors' directories, which the holder reads as paths "+
			"the controller fills; it is not yet a collection (design 57 L1)", name)
	case s.Name != canonicalSeat(seat):
		return "", true, fmt.Errorf("%s names the seat by another name; a collection names it %s", name, s.Name)
	}
	return r.Comment, true, nil
}

// isOld is whether a collection's name is an old namespace's.
func isOld(name string) bool {
	_, old, _ := oldCollection(name, true)
	return old
}

// collectedPlaceholderProblems is what is wrong with one resource's ${collected:…}: placed only in a file's content,
// and naming a collection the module declares it collects.
func collectedPlaceholderProblems(m mcat.Manifest, r map[string]any) []string {
	var problems []string
	for _, field := range sortedKeys(r) {
		v, ok := r[field].(string)
		if !ok {
			continue
		}
		for _, f := range ofCollected.FindAllStringSubmatch(v, -1) {
			base, selector := splitSelector(f[1])
			if _, err := selectorOf(selector); err != nil {
				problems = append(problems, fmt.Sprintf("%s's resource %v names %s: %v", m.Module, r["id"], f[0], err))
				continue
			}
			switch {
			case field != "content":
				problems = append(problems, fmt.Sprintf("%s's resource %v names %s in its %s; a collection is placed "+
					"only in a file's content", m.Module, r["id"], f[0], field))
			case isOld(base):
				if _, _, wrong := oldCollection(base, false); wrong != nil {
					problems = append(problems, fmt.Sprintf("%s's resource %v names %s: %v", m.Module, r["id"], f[0], wrong))
				}
			case !slices.ContainsFunc(m.Collections, func(c mcat.Collection) bool { return c.Name == base }):
				problems = append(problems, fmt.Sprintf("%s's resource %v names %s, and %s does not collect %q: "+
					"declare it under collections (novox/hq ADR 0349 §13)", m.Module, r["id"], f[0], m.Module, base))
			}
		}
	}
	return problems
}

// collectionComment is the comment of a collection a module's file names: declared, or the old namespace's.
func collectionComment(m mcat.Manifest, name string) (string, error) {
	if comment, old, wrong := oldCollection(name, false); old {
		return comment, wrong
	}
	for _, c := range m.Collections {
		if c.Name == name {
			return c.Comment, nil
		}
	}
	return "", fmt.Errorf("%s names ${collected:%s} and does not collect it", m.Module, name)
}

// itemsLeftOutFor is itemsLeftOut for a placeholder that selects by attributes (where), on a machine with these
// capabilities: an item the selector does not take, or whose capability the machine lacks, is not left out but not
// wanted here.
func itemsLeftOutFor(modules []mcat.Manifest, holder mcat.Manifest, collection string, where map[string]string,
	facts map[string]string, caps map[string]bool) []string {
	var out []string
	for _, m := range inModuleOrder(modules) {
		for _, it := range itemsInOrder(m.Items) {
			if it.Collection != collection || !itemMatches(it, where) || (it.IfCapability != "" && !caps[it.IfCapability]) {
				continue
			}
			if _, rendered := heldText(it, facts); rendered && renderedOldWay(collection) {
				continue
			}
			out = append(out, fmt.Sprintf("%s's item of %s is not placed: %s is filled the old way on this "+
				"machine, from contributions, and an item only by the provisioner's client (design 57 L1)",
				m.Module, itemKey(it), holder.Module))
		}
	}
	return out
}

// oldFormsLeftOut says each piece of an old form a handed collector's collections would have held: the collector is
// filled from items alone, and the piece's module contributes none (ADR 0349 clause 17).
func oldFormsLeftOut(modules []mcat.Manifest, holder mcat.Manifest, collections []mcat.PlanCollection) []string {
	var out []string
	for _, c := range collections {
		namespace, key, _ := strings.Cut(c.Name, ":")
		for _, m := range inModuleOrder(modules) {
			old := false
			switch namespace {
			case "shell":
				target, slot, _ := strings.Cut(key, ":")
				old = slices.ContainsFunc(m.Shell, func(s mcat.ShellCode) bool { return s.For == target && s.Slot == slot })
			case "environment":
				old = m.Environment != nil && (len(m.Environment.Variables) > 0 || len(m.Environment.Path) > 0)
			case "contribution":
				seat, kind, _ := strings.Cut(key, ":")
				old = slices.ContainsFunc(manifestAllContributions(m), func(s mcat.SeatContribution) bool {
					return canonicalSeat(s.Seat) == canonicalSeat(seat) && s.Kind == kind
				})
			}
			if old {
				out = append(out, fmt.Sprintf("%s's %s is not placed: %s is filled by the provisioner's client on "+
					"this machine, from items, and %s contributes it the old way (design 57 L1)", m.Module, c.Name,
					holder.Module, m.Module))
			}
		}
	}
	return out
}

// renderedOldWay is whether the controller renders a collection's items into a collector not handed.
func renderedOldWay(collection string) bool {
	namespace, _, _ := strings.Cut(collection, ":")
	return namespace == "shell" || namespace == "contribution" || namespace == mcat.EnvironmentCollection
}

// heldItem is one item of a module rendered the old way.
type heldItem struct {
	item mcat.Item
	text string
}

// heldItems is a module's items of the collection that the selector takes and the machine's capabilities allow, by
// order then name, each rendered as heldText does; the ones it cannot render are left out (itemsLeftOutFor says so).
func heldItems(m mcat.Manifest, collection string, where map[string]string, facts map[string]string,
	caps map[string]bool) []heldItem {
	if !renderedOldWay(collection) {
		return nil
	}
	var out []heldItem
	for _, it := range itemsInOrder(m.Items) {
		if it.Collection != collection || !itemMatches(it, where) || (it.IfCapability != "" && !caps[it.IfCapability]) {
			continue
		}
		if text, ok := heldText(it, facts); ok {
			out = append(out, heldItem{item: it, text: text})
		}
	}
	return out
}

// heldText is an item's text with the machine's facts filled, ending its line; false for an item whose text the mesh
// does not hold or which names anything but a machine fact this machine has.
func heldText(it mcat.Item, facts map[string]string) (string, bool) {
	if it.Content == "" {
		return "", false
	}
	text := it.Content
	for _, f := range templatePlaceholder.FindAllStringSubmatch(text, -1) {
		value, has := facts[f[2]]
		if f[1] != "machine" || !has {
			return "", false
		}
		text = strings.ReplaceAll(text, f[0], value)
	}
	if !strings.HasSuffix(text, "\n") {
		text += "\n"
	}
	return text, true
}