// Package classify extracts build targets from release asset filenames.
//
// Standard toolchains (goreleaser, cargo-dist, zig build) produce predictable
// filenames like "tool_0.1.0_linux_amd64.tar.gz" or
// "tool-0.1.0-x86_64-unknown-linux-musl.tar.gz". This package matches those
// patterns directly using regex, avoiding heuristic guessing.
//
// Detection order matters: architectures are checked longest-first to prevent
// "x86" from matching inside "x86_64", and OS checks use word boundaries.
package classify

import (
	"path"
	"regexp"
	"strings"

	"github.com/webinstall/webi-installers/internal/buildmeta"
)

// Result holds the classification of an asset filename.
type Result struct {
	OS     buildmeta.OS
	Arch   buildmeta.Arch
	Libc   buildmeta.Libc
	Format buildmeta.Format
}

// Target returns the build target (OS + Arch + Libc).
func (r Result) Target() buildmeta.Target {
	return buildmeta.Target{OS: r.OS, Arch: r.Arch, Libc: r.Libc}
}

// Filename classifies a release asset filename, returning the detected
// OS, architecture, libc, and archive format. Undetected fields are empty.
//
// OS is detected first because it can influence arch interpretation.
// For example, "windows-arm" in modern releases means ARM64, while
// bare "arm" on Linux historically means ARMv6.
func Filename(name string) Result {
	lower := strings.ToLower(name)
	os := detectOS(lower)
	arch := detectArch(lower)

	// On Windows, bare "arm" (detected as ARMv6) almost certainly means
	// ARM64. Windows never shipped ARMv6 binaries — "ARM" became the
	// marketing label for ARM64 (Windows on ARM).
	if os == buildmeta.OSWindows && arch == buildmeta.ArchARMv6 {
		arch = buildmeta.ArchARM64
	}

	return Result{
		OS:     os,
		Arch:   arch,
		Libc:   detectLibc(lower),
		Format: detectFormat(lower),
	}
}

// b is a boundary: start/end of string or a non-alphanumeric separator.
// Go's RE2 doesn't support \b, so we use this instead.
const b = `(?:^|[^a-zA-Z0-9])`
const bEnd = `(?:[^a-zA-Z0-9]|$)`

// --- OS detection ---

var osPatterns = []struct {
	os      buildmeta.OS
	pattern *regexp.Regexp
}{
	{buildmeta.OSDarwin, regexp.MustCompile(`(?i)` + b + `(?:darwin|macos|osx|os-x|apple)` + bEnd)},
	{buildmeta.OSLinux, regexp.MustCompile(`(?i)` + b + `linux` + bEnd)},
	{buildmeta.OSWindows, regexp.MustCompile(`(?i)` + b + `(?:windows|win(?:32|64|dows)?)` + bEnd + `|\.exe(?:\.xz)?$|\.msi$`)},
	{buildmeta.OSFreeBSD, regexp.MustCompile(`(?i)` + b + `freebsd` + bEnd)},
	{buildmeta.OSSunOS, regexp.MustCompile(`(?i)` + b + `(?:sunos|solaris|illumos)` + bEnd)},
	{buildmeta.OSAIX, regexp.MustCompile(`(?i)` + b + `aix` + bEnd)},
	{buildmeta.OSAndroid, regexp.MustCompile(`(?i)` + b + `android` + bEnd)},
}

func detectOS(lower string) buildmeta.OS {
	for _, p := range osPatterns {
		if p.pattern.MatchString(lower) {
			return p.os
		}
	}
	return ""
}

// --- Arch detection ---
// Order matters: check longer/more-specific patterns first.

var archPatterns = []struct {
	arch    buildmeta.Arch
	pattern *regexp.Regexp
}{
	// amd64 micro-levels before baseline — "amd64v3" must not fall through to amd64.
	{buildmeta.ArchAMD64v4, regexp.MustCompile(`(?i)(?:x86[_-]64[_-]v4|amd64v4|v4-amd64)`)},
	{buildmeta.ArchAMD64v3, regexp.MustCompile(`(?i)(?:x86[_-]64[_-]v3|amd64v3|v3-amd64)`)},
	{buildmeta.ArchAMD64v2, regexp.MustCompile(`(?i)(?:x86[_-]64[_-]v2|amd64v2|v2-amd64)`)},
	// amd64 baseline before x86 — "x86_64" must not match as x86.
	{buildmeta.ArchAMD64, regexp.MustCompile(`(?i)(?:x86[_-]64|amd64|x64|64-bit)`)},
	// arm64 before armv7/armv6 — "aarch64" must not match as arm.
	{buildmeta.ArchARM64, regexp.MustCompile(`(?i)(?:aarch64|arm64|armv8)`)},
	{buildmeta.ArchARMv7, regexp.MustCompile(`(?i)(?:armv7l?|arm-?v7|arm32)`)},
	{buildmeta.ArchARMv6, regexp.MustCompile(`(?i)(?:armv6l?|arm-?v6|aarch32|` + b + `arm` + bEnd + `)`)},
	// ppc64le before ppc64.
	{buildmeta.ArchPPC64LE, regexp.MustCompile(`(?i)ppc64le`)},
	{buildmeta.ArchPPC64, regexp.MustCompile(`(?i)ppc64`)},
	{buildmeta.ArchS390X, regexp.MustCompile(`(?i)s390x`)},
	{buildmeta.ArchMIPS64, regexp.MustCompile(`(?i)mips64`)},
	{buildmeta.ArchMIPS, regexp.MustCompile(`(?i)` + b + `mips` + bEnd)},
	// x86 last — must not steal x86_64.
	{buildmeta.ArchX86, regexp.MustCompile(`(?i)(?:` + b + `x86` + bEnd + `|i[3-6]86|32-bit)`)},
}

func detectArch(lower string) buildmeta.Arch {
	for _, p := range archPatterns {
		if p.pattern.MatchString(lower) {
			return p.arch
		}
	}
	return ""
}

// --- Libc detection ---

var (
	reMusl   = regexp.MustCompile(`(?i)` + b + `musl` + bEnd)
	reGNU    = regexp.MustCompile(`(?i)` + b + `(?:gnu|glibc)` + bEnd)
	reMSVC   = regexp.MustCompile(`(?i)` + b + `msvc` + bEnd)
	reStatic = regexp.MustCompile(`(?i)` + b + `static` + bEnd)
)

func detectLibc(lower string) buildmeta.Libc {
	switch {
	case reMusl.MatchString(lower):
		return buildmeta.LibcMusl
	case reGNU.MatchString(lower):
		return buildmeta.LibcGNU
	case reMSVC.MatchString(lower):
		return buildmeta.LibcMSVC
	case reStatic.MatchString(lower):
		return buildmeta.LibcNone
	}
	return ""
}

// --- Format detection ---

// formatSuffixes maps file extensions to formats, longest first.
var formatSuffixes = []struct {
	suffix string
	format buildmeta.Format
}{
	{".tar.gz", buildmeta.FormatTarGz},
	{".tar.xz", buildmeta.FormatTarXz},
	{".tar.zst", buildmeta.FormatTarZst},
	{".exe.xz", buildmeta.FormatExeXz},
	{".app.zip", buildmeta.FormatAppZip},
	{".tgz", buildmeta.FormatTarGz},
	{".zip", buildmeta.FormatZip},
	{".gz", buildmeta.FormatGz},
	{".xz", buildmeta.FormatXz},
	{".zst", buildmeta.FormatZst},
	{".7z", buildmeta.Format7z},
	{".exe", buildmeta.FormatExe},
	{".msi", buildmeta.FormatMSI},
	{".dmg", buildmeta.FormatDMG},
	{".pkg", buildmeta.FormatPkg},
}

func detectFormat(lower string) buildmeta.Format {
	// Use the base name to avoid directory separators confusing suffix matching.
	base := path.Base(lower)
	for _, s := range formatSuffixes {
		if strings.HasSuffix(base, s.suffix) {
			return s.format
		}
	}
	return ""
}