package engine

import (
	"encoding/json"
	"net/netip"
	"strings"

	"jarl/internal/iprange"
	"jarl/internal/model"
)

// ---- blocking steps and client groups (docs/blocking.md)

// stepRef resolves a step given by name or ID. ok is false when neither
// is given.
func stepRef(st *model.State, name *string, id *int64) (int64, bool, error) {
	switch {
	case name != nil:
		s, found := st.StepByName(*name)
		if !found {
			return 0, true, errf(KindBadRequest, "blocking step %q does not exist (steps: %s)", *name, stepNames(st))
		}
		return s, true, nil
	case id != nil:
		if _, found := st.StepRank(*id); !found {
			return 0, true, errf(KindBadRequest, "blocking step %d does not exist", *id)
		}
		return *id, true, nil
	}
	return 0, false, nil
}

// stepNames lists the steps for messages: "off, normal, strict".
func stepNames(st *model.State) string {
	names := []string{"off", "normal"}
	for _, s := range st.OrderedBlockSteps() {
		names = append(names, s.Name)
	}
	return strings.Join(names, ", ")
}

// NormalizeMember checks a client group member: an address, a prefix or
// an ACL name (an ACL's own elements are checked by validation). It
// returns the canonical form.
func NormalizeMember(st *model.State, m string) (string, error) {
	m = strings.TrimSpace(m)
	if a, err := netip.ParseAddr(m); err == nil {
		if a.Zone() != "" {
			return "", errf(KindBadRequest, "%q: an address with a zone can't be matched", m)
		}
		return a.Unmap().String(), nil
	}
	if p, err := netip.ParsePrefix(m); err == nil {
		return p.Masked().String(), nil
	}
	if r, ok, err := iprange.Parse(m); ok {
		if err != nil {
			return "", errf(KindBadRequest, "%v", err)
		}
		return r.String(), nil
	}
	if a := st.ACLByName(m); a != nil {
		return a.Name, nil
	}
	return "", errf(KindBadRequest, "%q is not an address, a prefix (10.10.0.0/24), a range (10.10.0.20-10.10.0.49) or an ACL", m)
}

func applyBlockStepPut(st *model.State, op model.Op, c *applyCtx) error {
	if err := c.require(blockingAction()); err != nil {
		return err
	}
	var in BlockStepInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	var s *model.BlockStep
	if op.Kind == OpBlockStepCreate {
		if op.ID <= 0 || st.BlockSteps[op.ID] != nil {
			return errf(KindConflict, "step ID %d is already in use", op.ID)
		}
		if in.Name == nil {
			return errf(KindBadRequest, "a blocking step needs a name")
		}
		pos := 0
		for _, o := range st.BlockSteps {
			pos = max(pos, o.Position+1)
		}
		s = &model.BlockStep{ID: op.ID, Position: pos}
	} else {
		s = st.BlockSteps[op.ID]
		if s == nil {
			return errf(KindNotFound, "blocking step %d does not exist", op.ID)
		}
		if err := checkVersion(op, s.Version, "step "+s.Name); err != nil {
			return err
		}
	}
	if in.Name != nil {
		name := strings.ToLower(strings.TrimSpace(*in.Name))
		if !blocklistNameRe.MatchString(name) || name == "off" || name == "normal" {
			return errf(KindBadRequest, "step name %q: use 1 to 40 lowercase letters, digits and hyphens, like strict (off and normal are built in)", *in.Name)
		}
		if id, found := st.StepByName(name); found && id != s.ID {
			return errf(KindConflict, "step %s already exists", name)
		}
		s.Name = name
	}
	if in.Position != nil {
		s.Position = *in.Position
	}
	if in.Comment != nil {
		s.Comment = *in.Comment
	}
	s.Touch(c.user(), c.now)
	st.BlockSteps[s.ID] = s
	return nil
}

func applyBlockStepDelete(st *model.State, op model.Op, c *applyCtx) error {
	if err := c.require(blockingAction()); err != nil {
		return err
	}
	s := st.BlockSteps[op.ID]
	if s == nil {
		return errf(KindNotFound, "blocking step %d does not exist", op.ID)
	}
	if err := checkVersion(op, s.Version, "step "+s.Name); err != nil {
		return err
	}
	if users := stepUsers(st, s.ID); len(users) > 0 {
		return errf(KindConflict, "step %s is used by %s; move them to another step first", s.Name, strings.Join(users, ", "))
	}
	delete(st.BlockSteps, s.ID)
	return nil
}

// stepUsers lists the blocklists and client groups at a step.
func stepUsers(st *model.State, id int64) []string {
	var out []string
	for _, b := range st.SortedBlocklists() {
		if b.StepID == id {
			out = append(out, "blocklist "+b.Name)
		}
	}
	for _, g := range st.SortedClientGroups() {
		if g.StepID == id {
			out = append(out, "client group "+g.Name)
		}
	}
	return out
}

func applyClientGroupPut(st *model.State, op model.Op, c *applyCtx) error {
	if err := c.require(blockingAction()); err != nil {
		return err
	}
	var in ClientGroupInput
	if err := decode(op.Data, &in); err != nil {
		return err
	}
	var g *model.ClientGroup
	if op.Kind == OpClientGroupCreate {
		if op.ID <= 0 || st.ClientGroups[op.ID] != nil {
			return errf(KindConflict, "client group ID %d is already in use", op.ID)
		}
		if in.Name == nil {
			return errf(KindBadRequest, "a client group needs a name")
		}
		g = &model.ClientGroup{ID: op.ID, Members: []string{}, StepID: model.StepNormal, ViewIDs: []int64{}}
	} else {
		g = st.ClientGroups[op.ID]
		if g == nil {
			return errf(KindNotFound, "client group %d does not exist", op.ID)
		}
		if err := checkVersion(op, g.Version, "client group "+g.Name); err != nil {
			return err
		}
	}
	if in.Name != nil {
		name := strings.ToLower(strings.TrimSpace(*in.Name))
		if !blocklistNameRe.MatchString(name) {
			return errf(KindBadRequest, "client group name %q: use 1 to 40 lowercase letters, digits and hyphens, like kids", *in.Name)
		}
		if other := st.ClientGroupByName(name); other != nil && other.ID != g.ID {
			return errf(KindConflict, "client group %s already exists", name)
		}
		g.Name = name
	}
	if in.Members != nil {
		members := []string{}
		seen := map[string]bool{}
		for _, m := range *in.Members {
			if strings.TrimSpace(m) == "" {
				continue
			}
			n, err := NormalizeMember(st, m)
			if err != nil {
				return err
			}
			if !seen[n] {
				seen[n] = true
				members = append(members, n)
			}
		}
		g.Members = members
	}
	step, given, err := stepRef(st, in.Step, in.StepID)
	if err != nil {
		return err
	}
	if given {
		g.StepID = step
	}
	ids, err := viewIDs(st, in.Views, in.ViewIDs)
	if err != nil {
		return err
	}
	if ids != nil {
		g.ViewIDs = ids
	}
	if in.Comment != nil {
		g.Comment = *in.Comment
	}
	g.Touch(c.user(), c.now)
	st.ClientGroups[g.ID] = g
	return nil
}

func applyClientGroupDelete(st *model.State, op model.Op, c *applyCtx) error {
	if err := c.require(blockingAction()); err != nil {
		return err
	}
	g := st.ClientGroups[op.ID]
	if g == nil {
		return errf(KindNotFound, "client group %d does not exist", op.ID)
	}
	if err := checkVersion(op, g.Version, "client group "+g.Name); err != nil {
		return err
	}
	delete(st.ClientGroups, g.ID)
	return nil
}

// ---- expansion

func (x *expander) blockStepCreate(req Request) ([]model.Op, error) {
	return x.simpleCreate(req, OpBlockStepCreate, func(data json.RawMessage) (string, error) {
		var in BlockStepInput
		if err := decode(data, &in); err != nil {
			return "", err
		}
		if in.Name == nil {
			return "", errf(KindBadRequest, "a blocking step needs a name")
		}
		return "add blocking step " + strings.ToLower(*in.Name), nil
	})
}

func (x *expander) clientGroupCreate(req Request) ([]model.Op, error) {
	return x.simpleCreate(req, OpClientGroupCreate, func(data json.RawMessage) (string, error) {
		var in ClientGroupInput
		if err := decode(data, &in); err != nil {
			return "", err
		}
		if in.Name == nil {
			return "", errf(KindBadRequest, "a client group needs a name")
		}
		return "add client group " + strings.ToLower(*in.Name), nil
	})
}