// Package forgeaccount is the forge accounts the mesh makes for its agents (novox/hq ADR 0365 clauses 1 and 3, ADR
// 0398 §1, ADR 0399, ADR 0400; issue 955): an account of the agent's own, no administrator, in the agents write
// team. Both the token tool (cmd/agent-token) and the forge-account provider use it, so there is one place that says
// what an agent's account is. It also makes the one account of the build modules' keys, nox-builder, in the builders
// team that reads the code of every repository and nothing else (ADR 0466 §3; issue 1481).
package forgeaccount

import (
	"context"
	"crypto/rand"
	"encoding/base64"
	"errors"
	"fmt"
	"net/http"
	"os"
	"regexp"

	"gitea/internal/forgehttp"
)

const (
	// AccountPrefix names an agent's account for its node (ADR 0365 §1).
	AccountPrefix = "agent-"
	// TeamOrg is the organisation whose repositories are the mesh's.
	TeamOrg = "novox"
	// TeamName is the one team every agent's account is in (ADR 0398 §1).
	TeamName = "agents"
)

// BuildersTeamName is the team of the build modules' account (ADR 0466 §3).
const BuildersTeamName = "builders"

// Team is a team of the organisation as the mesh keeps it: its name and the shape it is put back to.
type Team struct {
	Name  string
	Shape func() map[string]any
}

// AgentsTeam is the team of the machines' agents: write on code, issues and pull requests of every repository of the
// organisation and no more, the shape of the forge tools' team (tools-account.ts).
var AgentsTeam = Team{Name: TeamName, Shape: teamShape}

// BuildersTeam is the team of the build modules' account: it may read the code of every repository of the organisation
// and has no other right (ADR 0466 §3).
var BuildersTeam = Team{Name: BuildersTeamName, Shape: buildersTeamShape}

func teamShape() map[string]any {
	return map[string]any{
		"name": TeamName, "permission": "write", "includes_all_repositories": true, "can_create_org_repo": false,
		"units_map": map[string]string{"repo.code": "write", "repo.issues": "write", "repo.pulls": "write"},
	}
}

func buildersTeamShape() map[string]any {
	return map[string]any{
		"name": BuildersTeamName, "permission": "read", "includes_all_repositories": true, "can_create_org_repo": false,
		"units_map": map[string]string{"repo.code": "read"},
	}
}

// User is gitea's account as the admin reads it.
type User struct {
	IsAdmin       bool `json:"is_admin"`
	Active        bool `json:"active"`
	ProhibitLogin bool `json:"prohibit_login"`
	Restricted    bool `json:"restricted"`
}

// Accounts makes and keeps the agents' accounts with the administrator's login.
type Accounts struct {
	Forge forgehttp.Client
	// Password makes the password an account is created with: random, sent once and kept nowhere.
	Password func() string
	Log      func(format string, a ...any)
}

// EnsureAccount makes the agent's account, plain, when there is none, and puts back what was changed by hand: never
// an administrator, active, able to use its token. Its team is EnsureInTeam's.
func (m *Accounts) EnsureAccount(ctx context.Context, account string) error {
	var u User
	err := m.Forge.GetJSON(ctx, "/api/v1/users/"+account, &u)
	switch {
	case errors.Is(err, forgehttp.ErrNotFound):
		password := m.password()
		err := m.Forge.SendJSON(ctx, http.MethodPost, "/api/v1/admin/users", map[string]any{
			"username": account, "email": account + "@noreply.localhost", "password": password,
			"must_change_password": false, "visibility": "private",
		}, nil)
		password = ""
		if err != nil {
			return fmt.Errorf("the account %s could not be made: %w", account, err)
		}
		m.say("made the forge account %s for that machine's agent, in no team yet", account)
		return nil
	case err != nil:
		return fmt.Errorf("the account %s could not be read: %w", account, err)
	}
	if u.IsAdmin || !u.Active || u.ProhibitLogin {
		if err := m.Forge.SendJSON(ctx, http.MethodPatch, "/api/v1/admin/users/"+account, map[string]any{
			"login_name": account, "source_id": 0, "admin": false, "active": true, "prohibit_login": false,
		}, nil); err != nil {
			return fmt.Errorf("the account %s could not be made a plain account again: %w", account, err)
		}
		m.say("the account %s was changed by hand (administrator %t, active %t, login prohibited %t); made a plain account again",
			account, u.IsAdmin, u.Active, u.ProhibitLogin)
	}
	return nil
}

// EnsureInTeam makes the agents team when there is none, puts a team that is there back to its shape, and adds the
// account to it; an account already in it stays (ADR 0398 §1, issue 948).
func (m *Accounts) EnsureInTeam(ctx context.Context, account string) error {
	return m.EnsureInTeamOf(ctx, AgentsTeam, account)
}

// EnsureInTeamOf is EnsureInTeam for any team of the mesh's: it makes the team when there is none, puts a team that is
// there back to its shape, and adds the account to it.
func (m *Accounts) EnsureInTeamOf(ctx context.Context, team Team, account string) error {
	id, err := m.teamID(ctx, team.Name)
	if err != nil {
		return err
	}
	if id != 0 {
		if err := m.Forge.SendJSON(ctx, http.MethodPatch, fmt.Sprintf("/api/v1/teams/%d", id), team.Shape(), nil); err != nil {
			return fmt.Errorf("the team %s could not be put back to its shape: %w", team.Name, err)
		}
	} else {
		var made struct {
			ID int64 `json:"id"`
		}
		if err := m.Forge.SendJSON(ctx, http.MethodPost, "/api/v1/orgs/"+TeamOrg+"/teams", team.Shape(), &made); err != nil {
			return fmt.Errorf("the team %s could not be made: %w", team.Name, err)
		}
		id = made.ID
		m.say("made the forge team %s in %s", team.Name, TeamOrg)
	}
	if id == 0 {
		return fmt.Errorf("the forge answered no id for the team %s", team.Name)
	}
	if err := m.Forge.SendJSON(ctx, http.MethodPut, fmt.Sprintf("/api/v1/teams/%d/members/%s", id, account), nil, nil); err != nil {
		return fmt.Errorf("the account %s could not be added to the team %s: %w", account, team.Name, err)
	}
	return nil
}

// teamID is the id of the team of that name, or 0 when there is none.
func (m *Accounts) teamID(ctx context.Context, name string) (int64, error) {
	var id int64
	for page := 1; page <= 20 && id == 0; page++ {
		var teams []struct {
			ID   int64  `json:"id"`
			Name string `json:"name"`
		}
		if err := m.Forge.GetJSON(ctx, fmt.Sprintf("/api/v1/orgs/%s/teams?limit=50&page=%d", TeamOrg, page), &teams); err != nil {
			return 0, fmt.Errorf("the teams of %s could not be read: %w", TeamOrg, err)
		}
		for _, t := range teams {
			if t.Name == name {
				id = t.ID
			}
		}
		if len(teams) < 50 {
			break
		}
	}
	return id, nil
}

func (m *Accounts) password() string {
	if m.Password != nil {
		return m.Password()
	}
	b := make([]byte, 24)
	_, _ = rand.Read(b)
	return base64.RawURLEncoding.EncodeToString(b)
}

func (m *Accounts) say(format string, a ...any) {
	if m.Log != nil {
		m.Log(format, a...)
		return
	}
	fmt.Fprintf(os.Stderr, format+"\n", a...)
}

// NodeName is what a machine's name is, for it to name an account.
var NodeName = regexp.MustCompile(`^[a-z0-9][a-z0-9-]{0,31}$`)

// AgentUser is the one forge user of every machine's agents (ADR 0410 §1), in the agents write team.
const AgentUser = "nox-agent"

// BuilderUser is the one forge user of every build module's key (ADR 0466 §3), in the builders team: it reads and
// pushes nothing.
const BuilderUser = "nox-builder"

// BuildModules are the modules whose keys are the builders' (kind builder), by their name, which is also the name of
// the account each runs as (ADR 0466 §1).
var BuildModules = []string{"mesh-build-go", "mesh-build-node"}

// KindOfModule is the kind of key a consumer module's entry is made for: builder for a build module, machine for any
// other (ssh-client's).
func KindOfModule(module string) string {
	for _, m := range BuildModules {
		if m == module {
			return "builder"
		}
	}
	return "machine"
}

// ForgeUser is the forge user of a key of the given kind (ADR 0410 §1, ADR 0466 §3): `nox-agent` for every machine
// and account (kind machine), `nox-builder` for every build module (kind builder). A kind not built yet has none, and
// the answer is empty. The machine's name must still be one an account could be named for.
func ForgeUser(node, kind string) string {
	if !NodeName.MatchString(node) {
		return ""
	}
	switch kind {
	case "machine":
		return AgentUser
	case "builder":
		return BuilderUser
	}
	return ""
}

// TeamOfUser is the team a forge user of the mesh is in.
func TeamOfUser(user string) Team {
	if user == BuilderUser {
		return BuildersTeam
	}
	return AgentsTeam
}

// NodeAccount is the forge account the token tool (cmd/agent-token) keeps for a node's agent: `agent-<node>` (ADR
// 0365 §1). It is not the forge user of the machine's ssh key (ForgeUser), and its behaviour is unchanged.
func NodeAccount(node string) string { return AccountPrefix + node }