package main

// What the mesh installs (novox/hq ADR 0316 §1–§9, to-be 56 §1–§3): Betterbird from its pinned upstream release
// in /opt/betterbird, where the community package betterbird-bin put it, so Betterbird keeps choosing the same
// profile; the enterprise policy in its distribution directory, which turns Betterbird's own updater off and
// installs Owl into every profile from the xpi the mesh placed beside it; and a defaults file naming the
// system's spelling dictionaries. The tools read these files and say what they find: the version against the
// pin and the newest published build, whether the policy is placed, Owl's version against its pin.
//
// **The pin on the machine is what the mesh placed.** The manifest pins the release and the xpi by sha256; the
// node-engine places exactly those bytes, so the version in /opt/betterbird/application.ini (when the mesh
// placed it) and the version in the placed xpi are the pins. The community package's own copy is said as
// such, and the switch from it waits for the operator (ADR 0316 §4).

import (
	"archive/zip"
	"encoding/json"
	"fmt"
	"io"
	"net/http"
	"path/filepath"
	"strings"
	"time"
)

const (
	installDir = "/opt/betterbird"
	// policyFile is the enterprise policy the module places (ADR 0316 §7).
	policyFile = installDir + "/distribution/policies.json"
	// owlFile is Owl's xpi as the mesh placed it, and the URL the policy installs it from.
	owlFile = installDir + "/owl/owl.xpi"
	owlID   = "owl@beonex.com"
	// defaultClientPref is Betterbird's ask at its start to be the default mail, news, feed and calendar
	// client (Thunderbird's all-thunderbird.js: pref("mail.shell.checkDefaultClient", true); messenger.js opens
	// systemIntegrationDialog.xhtml while it is true). The module's policy locks it off (novox/hq issue 345).
	defaultClientPref = "mail.shell.checkDefaultClient"
	// preparation is the tools' program as the module places it for its start (betterbird-tools prepare).
	preparation = "/usr/local/lib/mesh-betterbird/betterbird-tools"
	// versionsURL is where Betterbird publishes its newest build per major version: what its own updater
	// reads (MailGlue's BetterbirdUpdateCheck), and what the status compares the installed build with.
	versionsURL = "https://www.betterbird.eu/start/versions.txt"
)

// publishedBuilds fetches Betterbird's list of newest builds: a variable so a test answers.
var publishedBuilds = func() (string, error) {
	client := &http.Client{Timeout: 5 * time.Second}
	resp, err := client.Get(versionsURL)
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()
	if resp.StatusCode != http.StatusOK {
		return "", fmt.Errorf("%s answered %s", versionsURL, resp.Status)
	}
	body, err := io.ReadAll(io.LimitReader(resp.Body, 1<<20))
	return string(body), err
}

// Installation is what is installed, and from where.
type Installation struct {
	// From is the mesh, the community package (betterbird-bin, before the switch), or nothing.
	From    string `json:"from"`
	Version string `json:"version,omitempty"`
	Build   string `json:"build,omitempty"`
	// Newest is the newest build Betterbird published for this major version, and whether this one is behind.
	Newest string `json:"newest_published_build,omitempty"`
	Behind bool   `json:"behind,omitempty"`
	// Policy says whether the module's enterprise policy is placed, and what it does.
	Policy string `json:"policy"`
	// Owl is the add-on's version as the mesh placed it (the pin), and as the profile runs it.
	Owl *OwlState `json:"owl,omitempty"`
}

// OwlState is Owl against its pin.
type OwlState struct {
	Pinned    string `json:"pinned,omitempty"`
	InProfile string `json:"in_profile,omitempty"`
	Active    bool   `json:"active"`
	AtThePin  bool   `json:"at_the_pin"`
	// Note says, as a fact, a profile running an Owl newer than the pin: the policy's install keeps a newer
	// version, and Owl installed by policy cannot be removed in Betterbird.
	Note string `json:"note,omitempty"`
}

// newerVersion says whether version a is newer than b, comparing dotted numbers.
func newerVersion(a, b string) bool {
	if a == "" || b == "" {
		return false
	}
	pa, pb := strings.Split(a, "."), strings.Split(b, ".")
	for i := 0; i < len(pa) || i < len(pb); i++ {
		var x, y int
		if i < len(pa) {
			fmt.Sscanf(pa[i], "%d", &x)
		}
		if i < len(pb) {
			fmt.Sscanf(pb[i], "%d", &y)
		}
		if x != y {
			return x > y
		}
	}
	return false
}

// installation reads what is installed. profile may be empty when none is found yet.
func (m *Machine) installation(profile string) Installation {
	var in Installation
	community, _ := m.installed(packageFor)
	raw, err := readBounded(m.path(appIni))
	switch {
	case community != "":
		in.From = "the community package " + packageFor + " " + community + ": the switch to the mesh's release waits for the operator's push, with Betterbird quit (novox/hq ADR 0316 §4)"
	case err == nil:
		in.From = "the mesh"
	default:
		in.From = "not installed"
	}
	if err == nil {
		_, sec := iniSections(raw)
		in.Version, in.Build = sec["App"]["Version"], sec["App"]["BuildID"]
		in.Newest, in.Behind = newestBuild(in.Version, in.Build)
	}
	in.Policy = m.policyState()
	pinned := xpiVersion(m.path(owlFile))
	owl := &OwlState{Pinned: pinned}
	if profile != "" {
		for _, a := range addOns(profile) {
			if a.ID == owlID {
				owl.InProfile, owl.Active = a.Version, a.Active
			}
		}
	}
	owl.AtThePin = owl.Pinned != "" && owl.Pinned == owl.InProfile
	if newerVersion(owl.InProfile, owl.Pinned) {
		owl.Note = "the profile runs Owl " + owl.InProfile + ", newer than the mesh's pin " + owl.Pinned + ": the policy " +
			"keeps a newer version and installs the pin only where Owl is missing. To run the same Owl everywhere, " +
			"move the module's pin in a reviewed change"
	}
	if owl.Pinned != "" || owl.InProfile != "" {
		in.Owl = owl
	}
	return in
}

// newestBuild is the newest build Betterbird published for a version's major, and whether build is older.
func newestBuild(version, build string) (string, bool) {
	major, _, _ := strings.Cut(version, ".")
	if major == "" || build == "" {
		return "", false
	}
	list, err := publishedBuilds()
	if err != nil {
		return "unknown: " + err.Error(), false
	}
	for _, l := range strings.Split(list, "\n") {
		f := strings.Split(strings.TrimSpace(l), ",")
		if len(f) == 3 && f[0] == "Linux" && f[1] == major {
			return f[2], f[2] > build
		}
	}
	return "unknown: " + versionsURL + " names no build for " + major, false
}

// policyState says whether the module's policy is placed and does what ADR 0316 §5 and §7 and issue 345 ask.
func (m *Machine) policyState() string {
	raw, err := readBounded(m.path(policyFile))
	if err != nil {
		return "not placed: " + policyFile + " is missing"
	}
	if why := policyProblem(raw); why != "" {
		return "placed, and " + why
	}
	return "placed: Betterbird's updater, its telemetry and add-on updates off, Owl installed into every profile from " +
		"the mesh's xpi with its updates off, and the ask to be the default mail client, the vendor's in-app notices " +
		"and the start page locked off"
}

// lockedOff are the preferences the module's policy locks to false (novox/hq issue 345), each with what it is.
var lockedOff = []struct{ Name, What string }{
	{defaultClientPref, "the ask to be the default mail client"},
	{"mail.inappnotifications.enabled", "the vendor's in-app notices"},
	{"mailnews.start_page.enabled", "the start page, loaded from the vendor at every start"},
}

// policyProblem is everything the policy fails to say of what ADR 0316 and issue 345 ask, or "".
func policyProblem(raw []byte) string {
	var p struct {
		Policies struct {
			DisableAppUpdate  bool  `json:"DisableAppUpdate"`
			DisableTelemetry  bool  `json:"DisableTelemetry"`
			ExtensionUpdate   *bool `json:"ExtensionUpdate"`
			ExtensionSettings map[string]struct {
				Mode     string `json:"installation_mode"`
				URL      string `json:"install_url"`
				Disabled bool   `json:"updates_disabled"`
			} `json:"ExtensionSettings"`
		} `json:"policies"`
	}
	if err := json.Unmarshal(raw, &p); err != nil {
		return "it is not JSON: " + err.Error()
	}
	var problems []string
	if !p.Policies.DisableAppUpdate {
		problems = append(problems, "it does not turn Betterbird's updater off (DisableAppUpdate)")
	}
	if !p.Policies.DisableTelemetry {
		problems = append(problems, "it does not turn telemetry off (DisableTelemetry)")
	}
	if p.Policies.ExtensionUpdate == nil || *p.Policies.ExtensionUpdate {
		problems = append(problems, "it leaves add-ons updating themselves (ExtensionUpdate)")
	}
	owl, ok := p.Policies.ExtensionSettings[owlID]
	switch {
	case !ok || owl.Mode != "force_installed":
		problems = append(problems, "it does not install Owl into every profile (force_installed)")
	case owl.URL != "file://"+owlFile:
		problems = append(problems, "it installs Owl from "+owl.URL+", not from the mesh's xpi")
	case !owl.Disabled:
		problems = append(problems, "it leaves Owl's updates on")
	}
	prefs := policyPrefsOf(raw)
	for _, l := range lockedOff {
		if pr, ok := prefs[l.Name]; !ok || pr.Value != "false" || !pr.Locked {
			problems = append(problems, "it does not lock "+l.What+" off (Preferences "+l.Name+": false, locked)")
		}
	}
	return strings.Join(problems, "; ")
}

// defaultClientAsk says why Betterbird asks at its start to be the default mail client, or "" when it does
// not: the placed policy's own Preferences entry locks the ask off, else the profile's user.js (which wins at
// the start) or prefs.js turns it off. Betterbird's own default is to ask. Decided from the entry itself, never
// from what else the policy lacks.
func (m *Machine) defaultClientAsk(profile string) string {
	if v, ok := m.locks()[defaultClientPref]; ok && v == "false" {
		return ""
	}
	if profile != "" {
		for _, f := range []string{"user.js", "prefs.js"} {
			b, err := readBounded(filepath.Join(profile, f))
			if err != nil {
				continue
			}
			if v, ok := statementsOf(b)[defaultClientPref]; ok {
				if v == "false" {
					return ""
				}
				return "the profile's " + f + " sets " + defaultClientPref + " to " + v + " and no policy locks it off"
			}
		}
	}
	return "no policy locks " + defaultClientPref + " off and Betterbird's default is to ask"
}

// xpiVersion is the version an add-on's manifest.json says, or "" when it cannot be read.
func xpiVersion(path string) string {
	r, err := zip.OpenReader(path)
	if err != nil {
		return ""
	}
	defer r.Close()
	for _, f := range r.File {
		if f.Name != "manifest.json" {
			continue
		}
		rc, err := f.Open()
		if err != nil {
			return ""
		}
		defer rc.Close()
		var mf struct {
			Version string `json:"version"`
		}
		if json.NewDecoder(io.LimitReader(rc, 1<<20)).Decode(&mf) != nil {
			return ""
		}
		return mf.Version
	}
	return ""
}

// addOns reads a profile's extensions.json: each add-on's id, version, whether it is on, and where from.
func addOns(profile string) []AddOn {
	raw, err := readBounded(filepath.Join(profile, "extensions.json"))
	if err != nil {
		return nil
	}
	var ext struct {
		Addons []struct {
			ID       string `json:"id"`
			Version  string `json:"version"`
			Active   bool   `json:"active"`
			Location string `json:"location"`
		} `json:"addons"`
	}
	if json.Unmarshal(raw, &ext) != nil {
		return nil
	}
	var out []AddOn
	for _, a := range ext.Addons {
		if a.Location == "app-profile" {
			out = append(out, AddOn{ID: a.ID, Version: a.Version, Active: a.Active})
		}
	}
	return out
}