package main

// Reading the package manager (novox/hq to-be 42 Phase 1, research 026/05): what is installed and
// why, what a search finds, what owns a path, what a package holds, what is orphaned or foreign.
// Every one of these reads the local or sync databases, which any account may; none escalates.

import (
	"fmt"
	"path"
	"regexp"
	"sort"
	"strings"
)

// Found is one package a search found.
type Found struct {
	Repository  string   `json:"repository"`
	Name        string   `json:"name"`
	Version     string   `json:"version"`
	Groups      []string `json:"groups,omitempty"`
	Installed   bool     `json:"installed"`
	InstalledAs string   `json:"installed_version,omitempty"`
	Description string   `json:"description"`
}

var searchHeader = regexp.MustCompile(`^(\S+)/(\S+) (\S+)(?: \(([^)]*)\))?(?: \[installed(?:: ([^\]]+))?\])?$`)

// ParseSearch reads `pacman -Ss`: a header line per package and its description indented beneath.
func ParseSearch(out string) []Found {
	found := []Found{}
	for _, l := range strings.Split(out, "\n") {
		if strings.TrimSpace(l) == "" {
			continue
		}
		if strings.HasPrefix(l, " ") {
			if n := len(found); n > 0 {
				found[n-1].Description = strings.TrimSpace(strings.TrimSpace(found[n-1].Description + " " + strings.TrimSpace(l)))
			}
			continue
		}
		m := searchHeader.FindStringSubmatch(l)
		if m == nil {
			continue
		}
		f := Found{Repository: m[1], Name: m[2], Version: m[3], Installed: strings.Contains(l, "[installed")}
		if m[4] != "" {
			f.Groups = strings.Fields(m[4])
		}
		if f.Installed {
			f.InstalledAs = f.Version
			if m[5] != "" {
				f.InstalledAs = m[5]
			}
		}
		found = append(found, f)
	}
	return found
}

// none is pacman's way of saying a query found nothing: status 1 and nothing said.
func none(r Ran) bool {
	return r.Status == 1 && r.Err == "" && strings.TrimSpace(r.Stdout+r.Stderr) == ""
}

// query runs a pacman query whose empty answer is status 1, and fails only on a real failure.
func (m *Machine) query(args ...string) (string, error) {
	r := m.Run(bg(), "pacman", args...)
	if r.Status == 0 && r.Err == "" {
		return r.Stdout, nil
	}
	if none(r) {
		return "", nil
	}
	return "", failure("pacman", "pacman", r)
}

// Search is `pacman -Ss` over the sync databases, bounded.
func (m *Machine) Search(words string, limit int) (map[string]any, error) {
	out, err := m.query(append([]string{"-Ss", "--"}, strings.Fields(words)...)...)
	if err != nil {
		return nil, err
	}
	found := ParseSearch(out)
	return bound("packages", found, limit), nil
}

// bound is a list answered with its count, cut to a limit and saying so.
func bound[T any](key string, list []T, limit int) map[string]any {
	out := map[string]any{"count": len(list), "truncated": false}
	if limit > 0 && len(list) > limit {
		list = list[:limit]
		out["truncated"] = true
	}
	out[key] = list
	return out
}

// ParseInfo reads `pacman -Qi`/`-Si`: `Key : value` lines, continuation lines indented beneath.
// A field that is a list (two spaces between members) is answered as one, and "None" as empty.
func ParseInfo(out string) []map[string]any {
	var pkgs []map[string]any
	var cur map[string]any
	last := ""
	for _, l := range strings.Split(out, "\n") {
		if strings.TrimSpace(l) == "" {
			if cur != nil {
				pkgs = append(pkgs, cur)
				cur = nil
			}
			continue
		}
		if cur == nil {
			cur = map[string]any{}
		}
		if k, v, ok := strings.Cut(l, " : "); ok && !strings.HasPrefix(l, " ") {
			last = strings.TrimSpace(k)
			cur[last] = infoValue(last, strings.TrimSpace(v))
			continue
		}
		// A continuation: the optional dependencies, one per line.
		if last != "" {
			v := strings.TrimSpace(l)
			switch prev := cur[last].(type) {
			case []string:
				cur[last] = append(prev, v)
			case string:
				cur[last] = []string{prev, v}
			}
		}
	}
	if cur != nil {
		pkgs = append(pkgs, cur)
	}
	return pkgs
}

var listFields = map[string]bool{
	"Licenses": true, "Groups": true, "Provides": true, "Depends On": true, "Optional Deps": true,
	"Required By": true, "Optional For": true, "Conflicts With": true, "Replaces": true,
}

func infoValue(key, v string) any {
	if !listFields[key] {
		return v
	}
	if v == "None" {
		return []string{}
	}
	if key == "Optional Deps" {
		return []string{v}
	}
	return strings.Fields(v)
}

// Info is one package as the local database knows it, or the sync databases when it is not installed.
func (m *Machine) Info(name string) (map[string]any, error) {
	r := m.Run(bg(), "pacman", "-Qi", "--", name)
	installed := true
	if r.Status != 0 {
		if r.Err != "" || !strings.Contains(r.Stderr, "was not found") {
			return nil, failure("pacman", "pacman", r)
		}
		installed = false
		if r = m.Run(bg(), "pacman", "-Si", "--", name); r.Status != 0 || r.Err != "" {
			if strings.Contains(r.Stderr, "was not found") {
				return nil, fmt.Errorf("no package %s, installed or in a repository", name)
			}
			return nil, failure("pacman", "pacman", r)
		}
	}
	pkgs := ParseInfo(r.Stdout)
	if len(pkgs) == 0 {
		return nil, fmt.Errorf("pacman said nothing about %s", name)
	}
	return map[string]any{"installed": installed, "package": pkgs[0]}, nil
}

// Package is an installed package and why it is installed.
type Package struct {
	Name    string `json:"name"`
	Version string `json:"version"`
	Reason  string `json:"reason"`
	Foreign bool   `json:"foreign"`
}

func nameVersions(out string) [][2]string {
	var nv [][2]string
	for _, l := range lines(out) {
		if f := strings.Fields(l); len(f) >= 2 {
			nv = append(nv, [2]string{f[0], f[1]})
		}
	}
	return nv
}

func nameSet(out string) map[string]bool {
	s := map[string]bool{}
	for _, l := range lines(out) {
		s[strings.TrimSpace(l)] = true
	}
	return s
}

// Installed is every installed package with its version, whether it was installed explicitly or as
// a dependency, and whether it is foreign (in no repository this machine syncs).
func (m *Machine) Installed(match, reason string, foreignOnly bool, limit int) (map[string]any, error) {
	all, err := m.query("-Q")
	if err != nil {
		return nil, err
	}
	explicit, err := m.query("-Qeq")
	if err != nil {
		return nil, err
	}
	foreign, err := m.query("-Qmq")
	if err != nil {
		return nil, err
	}
	ex, fo := nameSet(explicit), nameSet(foreign)
	pkgs := []Package{}
	counts := map[string]int{"explicit": 0, "dependency": 0, "foreign": 0}
	for _, nv := range nameVersions(all) {
		p := Package{Name: nv[0], Version: nv[1], Reason: "dependency", Foreign: fo[nv[0]]}
		if ex[p.Name] {
			p.Reason = "explicit"
		}
		counts[p.Reason]++
		if p.Foreign {
			counts["foreign"]++
		}
		if match != "" && !strings.Contains(p.Name, match) || reason != "" && p.Reason != reason || foreignOnly && !p.Foreign {
			continue
		}
		pkgs = append(pkgs, p)
	}
	out := bound("packages", pkgs, limit)
	out["totals"] = counts
	return out, nil
}

var ownedBy = regexp.MustCompile(`^(.*) is owned by (\S+) (\S+)$`)

// Owns is which package owns a path.
func (m *Machine) Owns(p string) (map[string]any, error) {
	if !path.IsAbs(p) {
		return nil, fmt.Errorf("%q is not an absolute path", p)
	}
	r := m.Run(bg(), "pacman", "-Qo", "--", p)
	if r.Status == 0 && r.Err == "" {
		for _, l := range lines(r.Stdout) {
			if o := ownedBy.FindStringSubmatch(l); o != nil {
				return map[string]any{"path": o[1], "owned": true, "package": o[2], "version": o[3]}, nil
			}
		}
	}
	if r.Err == "" && strings.Contains(r.Stderr, "No package owns") {
		return map[string]any{"path": p, "owned": false}, nil
	}
	return nil, failure("pacman", "pacman", r)
}

// Files is what an installed package placed, bounded.
func (m *Machine) Files(name string, limit int) (map[string]any, error) {
	r := m.Run(bg(), "pacman", "-Ql", "--", name)
	if r.Status != 0 || r.Err != "" {
		if strings.Contains(r.Stderr, "was not found") {
			return nil, fmt.Errorf("%s is not installed", name)
		}
		return nil, failure("pacman", "pacman", r)
	}
	paths := []string{}
	for _, l := range lines(r.Stdout) {
		if _, p, ok := strings.Cut(l, " "); ok {
			paths = append(paths, p)
		}
	}
	out := bound("paths", paths, limit)
	out["package"] = name
	return out, nil
}

// Orphans are packages installed as dependencies that nothing requires any more.
func (m *Machine) Orphans() (map[string]any, error) {
	out, err := m.query("-Qdt")
	if err != nil {
		return nil, err
	}
	pkgs := []map[string]string{}
	for _, nv := range nameVersions(out) {
		pkgs = append(pkgs, map[string]string{"name": nv[0], "version": nv[1]})
	}
	return map[string]any{"count": len(pkgs), "orphans": pkgs}, nil
}

// Foreign is every installed package no repository this machine syncs carries: built from the AUR
// or by hand, which the host's `package` shape cannot install (research 027, question 1).
func (m *Machine) Foreign() (map[string]any, error) {
	out, err := m.query("-Qm")
	if err != nil {
		return nil, err
	}
	pkgs := []map[string]string{}
	for _, nv := range nameVersions(out) {
		pkgs = append(pkgs, map[string]string{"name": nv[0], "version": nv[1]})
	}
	sort.Slice(pkgs, func(i, j int) bool { return pkgs[i]["name"] < pkgs[j]["name"] })
	return map[string]any{"count": len(pkgs), "packages": pkgs}, nil
}

// Update is one package an upgrade would change.
type Update struct {
	Name string `json:"name"`
	From string `json:"from"`
	To   string `json:"to"`
}

var updateLine = regexp.MustCompile(`^(\S+) (\S+) -> (\S+)`)

// Updates is what a full upgrade would change, from checkupdates: a copy of the sync databases
// refreshed apart from the machine's own, so asking never makes a partial upgrade possible.
func (m *Machine) Updates() (map[string]any, error) {
	r := m.Run(bg(), "checkupdates")
	switch {
	case r.Err == "ENOENT":
		return nil, fmt.Errorf("checkupdates is not installed: it comes with pacman-contrib, which this module declares")
	case r.Err == "" && r.Status == 2:
		return map[string]any{"count": 0, "updates": []Update{}}, nil
	case r.Err != "" || r.Status != 0:
		return nil, failure("checkupdates", "checkupdates", r)
	}
	ups := []Update{}
	for _, l := range lines(r.Stdout) {
		if u := updateLine.FindStringSubmatch(strings.TrimSpace(l)); u != nil {
			ups = append(ups, Update{u[1], u[2], u[3]})
		}
	}
	return map[string]any{"count": len(ups), "updates": ups}, nil
}

// Config is the configuration pacman runs with, as pacman-conf resolves it.
type Config struct {
	Options      map[string][]string `json:"options"`
	Repositories []Repository        `json:"repositories"`
	MeshOwned    bool                `json:"mesh_owned"`
}

// Repository is one repository and where it is fetched from.
type Repository struct {
	Name        string `json:"name"`
	Servers     int    `json:"servers"`
	FirstServer string `json:"first_server,omitempty"`
	SigLevel    string `json:"sig_level,omitempty"`
}

// MeshHeader is how the module's pacman.conf begins, which is how it is recognised.
const MeshHeader = "# The mesh's (module pacman"

// ParseConf reads `pacman-conf`: [options] and each repository, with their values.
func ParseConf(out string) Config {
	c := Config{Options: map[string][]string{}, Repositories: []Repository{}}
	section := ""
	for _, l := range lines(out) {
		l = strings.TrimSpace(l)
		if strings.HasPrefix(l, "[") && strings.HasSuffix(l, "]") {
			section = strings.Trim(l, "[]")
			if section != "options" {
				c.Repositories = append(c.Repositories, Repository{Name: section})
			}
			continue
		}
		k, v, _ := strings.Cut(l, " = ")
		k, v = strings.TrimSpace(k), strings.TrimSpace(v)
		if section == "options" {
			c.Options[k] = append(c.Options[k], v)
			continue
		}
		if n := len(c.Repositories); n > 0 {
			r := &c.Repositories[n-1]
			switch k {
			case "Server":
				if r.Servers == 0 {
					r.FirstServer = v
				}
				r.Servers++
			case "SigLevel":
				r.SigLevel = strings.TrimSpace(r.SigLevel + " " + v)
			}
		}
	}
	return c
}

// Conf is pacman's configuration in force, and whether /etc/pacman.conf is the module's.
func (m *Machine) Conf() (Config, error) {
	out, err := m.Out("pacman-conf")
	if err != nil {
		return Config{}, err
	}
	c := ParseConf(out)
	if text, err := m.ReadFile("/etc/pacman.conf"); err == nil {
		c.MeshOwned = strings.HasPrefix(string(text), MeshHeader)
	}
	return c, nil
}