package impact

import (
	"path"
	"strings"
)

// Rules, as they appear in --json output and --explain.
const (
	RuleCommon         = "hieradata/common"
	RuleNode           = "hieradata/node"
	RuleRole           = "hieradata/role"
	RuleCountry        = "hieradata/country"
	RuleCountryRegion  = "hieradata/country-region"
	RuleCountryRegRole = "hieradata/country-region-role"
	RuleCountryRole    = "hieradata/country-role"
	RuleVirtual        = "hieradata/virtual"
	RuleOS             = "hieradata/os"
	RuleRepoGlobal     = "repo-global"
	RulePluginsync     = "pluginsync"
	RuleRoleClass      = "role-class"
	RuleHieraInclude   = "hiera_include"
	RuleUnmapped       = "unmapped"
	RuleClassReverse   = "class-reverse-lookup"
)

// repoGlobalFiles change classification or module resolution for the whole
// estate. Puppetfile pins external modules whose code is not in this repo, so
// it is deliberately mapped to every host rather than guessed at.
var repoGlobalFiles = map[string]bool{
	"hiera.yaml":       true,
	"environment.conf": true,
	"Puppetfile":       true,
	"Puppetfile.lock":  true,
}

// ignoredPrefixes hold paths outside the Puppet modulepath: CI, docs, specs
// and the bundler vendor tree. Nothing under them can reach a catalog.
var ignoredPrefixes = []string{
	".woodpecker/", ".github/", ".claude/", "ci/", "doc/", "docs/", "spec/", "vendor/", "examples/",
}

var ignoredFiles = map[string]bool{
	"Gemfile": true, "Gemfile.lock": true, "Rakefile": true,
	".rubocop.yml": true, ".reek.yml": true, ".pre-commit-config.yaml": true,
	".gitignore": true, ".fixtures.yml": true, ".ruby-version": true,
	"catalog_diff.py": true, "deploy.py": true,
}

// moduleSubdirIgnored are module subtrees that are not consulted during a
// catalog compile.
var moduleSubdirIgnored = map[string]bool{"spec": true, "examples": true, "doc": true, "docs": true}

// classRef is a class a changed file defines, awaiting reverse lookup.
type classRef struct {
	name string
	why  string
}

// mapping is what a single changed path resolves to before hosts are selected.
type mapping struct {
	targets []target
	classes []classRef
	ignored bool
	unknown bool
}

// classifyPath maps one repo-relative path onto selectors or classes. idx may
// be nil, in which case asset files fall back to their whole module.
func classifyPath(p string, idx *Index) mapping {
	p = path.Clean(strings.TrimPrefix(p, "./"))

	if repoGlobalFiles[p] {
		return mapping{targets: []target{allTarget(RuleRepoGlobal,
			fmtDetail("%s is repo-global; every catalog reads it", p))}}
	}
	if strings.HasPrefix(p, "manifests/") {
		return mapping{targets: []target{allTarget(RuleRepoGlobal,
			"the environment manifest applies to every node")}}
	}
	if ignoredFiles[p] || strings.HasSuffix(p, ".md") {
		return mapping{ignored: true}
	}
	for _, prefix := range ignoredPrefixes {
		if strings.HasPrefix(p, prefix) {
			return mapping{ignored: true}
		}
	}

	if rest, ok := strings.CutPrefix(p, "hieradata/"); ok {
		sel, rule, ok := hieradataSelector(rest)
		if !ok {
			return mapping{unknown: true}
		}
		return mapping{targets: []target{{sel: sel, rule: rule,
			detail: fmtDetail("hieradata file selects %s", sel)}}}
	}

	if strings.HasPrefix(p, "site/") || strings.HasPrefix(p, "modules/") {
		return classifyModulePath(p, idx)
	}

	return mapping{unknown: true}
}

// classifyModulePath handles everything under the modulepath roots: site/ (the
// roles and profiles modules) and modules/ (in-repo modules).
func classifyModulePath(p string, idx *Index) mapping {
	parts := strings.Split(p, "/")
	if len(parts) < 3 {
		return mapping{unknown: true}
	}
	module, subdir := parts[1], parts[2]
	rest := parts[3:]

	if moduleSubdirIgnored[subdir] {
		return mapping{ignored: true}
	}

	if subdir == "manifests" && len(rest) > 0 && strings.HasSuffix(rest[len(rest)-1], ".pp") {
		var classes []classRef
		for _, name := range ManifestClasses(module, rest) {
			classes = append(classes, classRef{name: name, why: fmtDetail("%s defines class %s", p, name)})
		}
		return mapping{classes: classes}
	}

	// lib/ and facts.d/ are pluginsynced to every agent, so a custom fact,
	// function or type there can move any catalog.
	if subdir == "lib" || subdir == "facts.d" {
		return mapping{targets: []target{allTarget(RulePluginsync,
			fmtDetail("%s is pluginsynced to every agent", p))}}
	}

	if subdir == "templates" || subdir == "files" {
		asset := module + "/" + strings.Join(rest, "/")
		if idx != nil {
			if owners := idx.AssetOwners(asset); len(owners) > 0 {
				var classes []classRef
				for _, name := range owners {
					classes = append(classes, classRef{name: name,
						why: fmtDetail("%s is referenced by class %s", p, name)})
				}
				return mapping{classes: classes}
			}
		}
		return moduleWide(p, module, idx, "no manifest references this asset")
	}

	return moduleWide(p, module, idx, fmtDetail("%s/ is module-wide", subdir))
}

// moduleWide attributes a file to every class its module defines. It is the
// deliberate over-include fallback for module data that cannot be traced to a
// single class.
func moduleWide(p, module string, idx *Index, why string) mapping {
	if idx == nil {
		return mapping{unknown: true}
	}
	names := idx.ModuleClasses(module)
	if len(names) == 0 {
		return mapping{unknown: true}
	}
	var classes []classRef
	for _, name := range names {
		classes = append(classes, classRef{name: name,
			why: fmtDetail("%s: %s, attributed to class %s", p, why, name)})
	}
	return mapping{classes: classes}
}

// ManifestClasses returns the class names a manifest file autoloads as. An
// init.pp is reachable both as the namespace itself and as <namespace>::init,
// and this repo uses both spellings.
func ManifestClasses(module string, rest []string) []string {
	segs := append([]string{module}, rest...)
	segs[len(segs)-1] = strings.TrimSuffix(segs[len(segs)-1], ".pp")

	full := strings.Join(segs, "::")
	if segs[len(segs)-1] != "init" {
		return []string{full}
	}
	short := strings.Join(segs[:len(segs)-1], "::")
	return []string{short, full}
}

// hieradataSelector maps a path under hieradata/ onto the facts the hiera
// hierarchy interpolates into it.
func hieradataSelector(rel string) (Selector, string, bool) {
	ext := path.Ext(rel)
	if ext != ".yaml" && ext != ".eyaml" {
		return Selector{}, "", false
	}
	parts := strings.Split(strings.TrimSuffix(rel, ext), "/")

	switch {
	case len(parts) == 1 && parts[0] == "common":
		return Selector{All: true}, RuleCommon, true

	case parts[0] == "nodes" && len(parts) == 2:
		return Selector{Certname: parts[1]}, RuleNode, true

	case parts[0] == "virtual" && len(parts) == 2:
		return Selector{Virtual: parts[1]}, RuleVirtual, true

	case parts[0] == "os" && len(parts) == 3:
		return osSelector(parts[1], parts[2]), RuleOS, true

	case parts[0] == "roles" && len(parts) >= 2 && len(parts) <= 4:
		return Selector{RoleTiers: parts[1:]}, RuleRole, true

	case parts[0] == "country" && len(parts) == 2:
		return Selector{Country: parts[1]}, RuleCountry, true

	case parts[0] == "country" && len(parts) == 4 && parts[2] == "region":
		return Selector{Country: parts[1], Region: parts[3]}, RuleCountryRegion, true

	case parts[0] == "country" && len(parts) >= 5 && len(parts) <= 7 && parts[2] == "region":
		return Selector{Country: parts[1], Region: parts[3], RoleTiers: parts[4:]}, RuleCountryRegRole, true

	case parts[0] == "country" && len(parts) >= 4 && len(parts) <= 6 && parts[2] == "roles":
		return Selector{Country: parts[1], RoleTiers: parts[3:]}, RuleCountryRole, true
	}

	return Selector{}, "", false
}

// osSelector reads os/<name>/<name><major>[.<minor>].yaml and its
// all_releases.yaml sibling.
func osSelector(osName, file string) Selector {
	sel := Selector{OSName: osName}
	if file == "all_releases" {
		return sel
	}
	version := file
	if len(file) >= len(osName) && strings.EqualFold(file[:len(osName)], osName) {
		version = file[len(osName):]
	}
	version = strings.TrimLeft(version, "-_")
	if version == "" {
		return sel
	}
	major, minor, hasMinor := strings.Cut(version, ".")
	sel.OSMajor = major
	if hasMinor {
		sel.OSMinor = minor
	}
	return sel
}