1 files changed, 388 insertions, 0 deletions
diff --git a/internal/cond/compile.go b/internal/cond/compile.go
new file mode 100644
index 0000000..4fdc75f
--- /dev/null
+++ b/internal/cond/compile.go
@@ -0,0 +1,388 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package cond
+
+import (
+	"errors"
+	"fmt"
+	"regexp"
+	"regexp/syntax"
+	"sort"
+	"strings"
+
+	"krino/internal/config"
+	"krino/internal/norm"
+	"krino/internal/sexp"
+)
+
+// maxDepth is the deepest a condition may nest; the top-level conditions
+// are depth 1.
+const maxDepth = 64
+
+// Compile compiles a rule's (when ...) conditions, applying cost-based
+// reordering. If it returns any diagnostic, the returned *Cond is nil: a
+// caller that ignores errs and calls Eval/Explain on the result panics
+// loudly, instead of silently treating a broken rule as "no conditions"
+// (always true).
+func Compile(file string, when []*sexp.Node, opt Options) (*Cond, []*config.Diag) {
+	c, errs := compile(file, when, opt, true)
+	if len(errs) > 0 {
+		return nil, errs
+	}
+	return c, errs
+}
+
+// compile is Compile with cost reordering switchable, for the property test
+// in Task 8.
+func compile(file string, when []*sexp.Node, opt Options, reorder bool) (*Cond, []*config.Diag) {
+	c := &compiler{file: file, opt: opt, reorder: reorder, cond: &Cond{opt: opt}}
+	var roots []*node
+	for _, n := range when {
+		if nd := c.compileNode(n, 1); nd != nil {
+			roots = append(roots, nd)
+		}
+	}
+	switch len(roots) {
+	case 0:
+		// no conditions: root stays nil, always true
+	case 1:
+		c.cond.root = roots[0]
+	default:
+		// several top-level conditions are an implicit and
+		c.cond.root = c.combine(kAnd, "and", roots, when[0].Pos)
+	}
+	return c.cond, c.errs
+}
+
+// compiler holds the state of one Compile call.
+type compiler struct {
+	file    string
+	opt     Options
+	reorder bool
+	cond    *Cond
+	errs    []*config.Diag
+}
+
+// errorf records a diagnostic at n's position; a nil n means the file as a
+// whole (unused here, kept for symmetry with config.diags).
+func (c *compiler) errorf(n *sexp.Node, format string, args ...any) {
+	var pos sexp.Pos
+	if n != nil {
+		pos = n.Pos
+	}
+	c.errs = append(c.errs, &config.Diag{File: c.file, Pos: pos, Msg: fmt.Sprintf(format, args...)})
+}
+
+// compileNode compiles one condition node at the given nesting depth (the
+// top-level conditions are depth 1). It returns nil, having recorded at
+// least one diagnostic, when n does not compile.
+func (c *compiler) compileNode(n *sexp.Node, depth int) *node {
+	if depth > maxDepth {
+		c.errorf(n, "conditions nest deeper than %d levels", maxDepth)
+		return nil
+	}
+	if n.Kind != sexp.List || n.Head() == "" {
+		c.errorf(n, "a condition is a form like (type pdf), not %s", n.String())
+		return nil
+	}
+	switch head := n.Head(); head {
+	case "and":
+		return c.compileCombiner(n, depth, kAnd, "and", "and needs at least one condition")
+	case "or":
+		return c.compileCombiner(n, depth, kOr, "or", "or needs at least one condition")
+	case "not":
+		return c.compileNot(n, depth)
+	case "type":
+		return c.compileType(n)
+	case "name":
+		return c.compileRegex(n, kName, "name")
+	case "path":
+		return c.compileRegex(n, kPath, "path")
+	case "content":
+		return c.compileContent(n)
+	case "size":
+		return c.compileSize(n)
+	case "age":
+		return c.compileAge(n)
+	case "duplicate":
+		return c.compileDuplicate(n)
+	case "matched":
+		return c.compileMatched(n)
+	default:
+		c.errorf(n, "unknown test (%s ...); tests are type, name, path, content, size, age, duplicate, matched, and, or, not", head)
+		return nil
+	}
+}
+
+// compileCombiner compiles (and ...) / (or ...): one or more child
+// conditions, cost-summed and cost-sorted (via combine).
+func (c *compiler) compileCombiner(n *sexp.Node, depth int, k kind, label, emptyMsg string) *node {
+	args := n.Args()
+	if len(args) == 0 {
+		c.errorf(n, "%s", emptyMsg)
+		return nil
+	}
+	children := make([]*node, 0, len(args))
+	for _, a := range args {
+		if ch := c.compileNode(a, depth+1); ch != nil {
+			children = append(children, ch)
+		}
+	}
+	return c.combine(k, label, children, n.Pos)
+}
+
+// combine builds an and/or node from already-compiled children: stable
+// cost-sort when reordering, cost is the sum of the children's.
+func (c *compiler) combine(k kind, label string, children []*node, pos sexp.Pos) *node {
+	if len(children) == 0 {
+		return nil
+	}
+	if c.reorder {
+		sort.SliceStable(children, func(i, j int) bool { return children[i].cost < children[j].cost })
+	}
+	cost := 0
+	for _, ch := range children {
+		cost += ch.cost
+	}
+	return &node{kind: k, pos: pos, label: label, children: children, cost: cost}
+}
+
+// compileNot compiles (not C): exactly one child condition.
+func (c *compiler) compileNot(n *sexp.Node, depth int) *node {
+	args := n.Args()
+	if len(args) != 1 {
+		c.errorf(n, "not takes exactly one condition")
+		return nil
+	}
+	child := c.compileNode(args[0], depth+1)
+	if child == nil {
+		return nil
+	}
+	return &node{kind: kNot, pos: n.Pos, label: "not", children: []*node{child}, cost: child.cost}
+}
+
+// compileType compiles (type T...): symbols, lower-cased; a group name
+// expands to its extensions, anything else is a literal (possibly
+// multi-part) extension.
+func (c *compiler) compileType(n *sexp.Node) *node {
+	args := n.Args()
+	if len(args) == 0 {
+		c.errorf(n, "type needs at least one extension or group, like (type pdf)")
+		return nil
+	}
+	var suffixes []string
+	bad := false
+	for _, a := range args {
+		if a.Kind != sexp.Symbol {
+			c.errorf(a, "type names are bare words: write (type pdf)")
+			bad = true
+			continue
+		}
+		lower := strings.ToLower(a.Text)
+		if exts, ok := groups[lower]; ok {
+			for _, e := range exts {
+				suffixes = append(suffixes, "."+e)
+			}
+		} else {
+			suffixes = append(suffixes, "."+lower)
+		}
+	}
+	if bad {
+		return nil
+	}
+	return &node{kind: kType, pos: n.Pos, label: argsLabel("type", args), cost: costCheap, suffixes: suffixes}
+}
+
+// compileRegex compiles (name "RE"...) / (path "RE"...).
+func (c *compiler) compileRegex(n *sexp.Node, k kind, test string) *node {
+	args := n.Args()
+	if len(args) == 0 {
+		c.errorf(n, "%s needs at least one regex in quotes", test)
+		return nil
+	}
+	var patterns []pattern
+	bad := false
+	for _, a := range args {
+		if a.Kind != sexp.String {
+			c.quotedExampleErr(a, test, "regexes")
+			bad = true
+			continue
+		}
+		src := a.Text
+		pat := src
+		if c.opt.Fold {
+			// E5: folding is applied to the regex source itself, not just
+			// to the text it is matched against - so a fold that expands
+			// one character into several changes the pattern's structure,
+			// not just its literal characters: "ß+" (one letter, a
+			// quantifier on it) becomes "ss+" (a quantifier on only the
+			// second "s") once norm.Fold expands "ß" to "ss", and likewise
+			// "æ" to "ae". A rule relying on repetition or anchoring
+			// around such a letter needs to account for this.
+			pat = norm.Fold(pat)
+		}
+		if c.opt.IgnoreCase {
+			pat = "(?i)" + pat
+		}
+		re, err := regexp.Compile(pat)
+		if err != nil {
+			var se *syntax.Error
+			if errors.As(err, &se) {
+				c.errorf(a, "%s: bad regex %q: %s", test, src, se.Code)
+			} else {
+				c.errorf(a, "%s: bad regex %q: %s", test, src, err)
+			}
+			bad = true
+			continue
+		}
+		patterns = append(patterns, pattern{re: re, src: src})
+	}
+	if bad {
+		return nil
+	}
+	return &node{kind: k, pos: n.Pos, label: argsLabel(test, args), cost: costRegex, patterns: patterns}
+}
+
+// compileContent compiles (content "KW"...): each keyword is normalised;
+// an empty result is an error.
+func (c *compiler) compileContent(n *sexp.Node) *node {
+	args := n.Args()
+	if len(args) == 0 {
+		c.errorf(n, "content needs at least one keyword in quotes")
+		return nil
+	}
+	var keywords []keyword
+	bad := false
+	for _, a := range args {
+		if a.Kind != sexp.String {
+			c.quotedExampleErr(a, "content", "keywords")
+			bad = true
+			continue
+		}
+		normed := norm.Text(a.Text, c.opt.IgnoreCase, c.opt.Fold)
+		if normed == "" {
+			c.errorf(a, "content keyword is empty")
+			bad = true
+			continue
+		}
+		keywords = append(keywords, keyword{norm: normed, src: a.Text})
+	}
+	if bad {
+		return nil
+	}
+	c.cond.UsesContent = true
+	return &node{kind: kContent, pos: n.Pos, label: argsLabel("content", args), cost: costContent, keywords: keywords}
+}
+
+// compileSize compiles (size OP SIZE).
+func (c *compiler) compileSize(n *sexp.Node) *node {
+	args := n.Args()
+	if len(args) != 2 || args[0].Kind != sexp.Symbol || args[1].Kind != sexp.Symbol {
+		c.errorf(n, "size takes an operator and a size, like (size > 10M)")
+		return nil
+	}
+	op := args[0].Text
+	bad := false
+	if !validOp(op) {
+		c.errorf(args[0], "size operator is one of > >= < <= =, not %s", op)
+		bad = true
+	}
+	val, err := config.ParseSize(args[1].Text)
+	if err != nil {
+		c.errorf(args[1], "size: %s", err)
+		bad = true
+	}
+	if bad {
+		return nil
+	}
+	return &node{kind: kSize, pos: n.Pos, label: argsLabel("size", args), cost: costCheap, op: op, sizeVal: val}
+}
+
+// compileAge compiles (age OP DURATION).
+func (c *compiler) compileAge(n *sexp.Node) *node {
+	args := n.Args()
+	if len(args) != 2 || args[0].Kind != sexp.Symbol || args[1].Kind != sexp.Symbol {
+		c.errorf(n, "age takes an operator and a duration, like (age > 30d)")
+		return nil
+	}
+	op := args[0].Text
+	bad := false
+	if !validOp(op) {
+		c.errorf(args[0], "age operator is one of > >= < <= =, not %s", op)
+		bad = true
+	}
+	val, err := config.ParseDuration(args[1].Text)
+	if err != nil {
+		c.errorf(args[1], "age: %s", err)
+		bad = true
+	}
+	if bad {
+		return nil
+	}
+	return &node{kind: kAge, pos: n.Pos, label: argsLabel("age", args), cost: costCheap, op: op, ageVal: val}
+}
+
+// validOp reports whether op is one of the size/age comparison operators.
+func validOp(op string) bool {
+	switch op {
+	case ">", ">=", "<", "<=", "=":
+		return true
+	}
+	return false
+}
+
+// compileDuplicate compiles (duplicate "DIR"...): zero or more directories,
+// stored raw for the engine to resolve. Every compiled test's list is
+// appended to Cond.DupDirs, in order.
+func (c *compiler) compileDuplicate(n *sexp.Node) *node {
+	args := n.Args()
+	dirs := make([]string, 0, len(args))
+	bad := false
+	for _, a := range args {
+		if a.Kind != sexp.String {
+			c.quotedExampleErr(a, "duplicate", "directories")
+			bad = true
+			continue
+		}
+		dirs = append(dirs, a.Text)
+	}
+	if bad {
+		return nil
+	}
+	c.cond.DupDirs = append(c.cond.DupDirs, dirs)
+	return &node{kind: kDuplicate, pos: n.Pos, label: argsLabel("duplicate", args), cost: costDuplicate, dirs: dirs}
+}
+
+// compileMatched compiles (matched): no arguments.
+func (c *compiler) compileMatched(n *sexp.Node) *node {
+	if len(n.Args()) != 0 {
+		c.errorf(n, "matched takes nothing: write (matched)")
+		return nil
+	}
+	return &node{kind: kMatched, pos: n.Pos, label: "matched", cost: costCheap}
+}
+
+// quotedExampleErr records the shared "takes X in quotes: write (test
+// "arg")" diagnostic used by name, path, content and duplicate.
+func (c *compiler) quotedExampleErr(a *sexp.Node, test, noun string) {
+	c.errorf(a, "%s takes %s in quotes: write (%s %s)", test, noun, test, sexp.Quote(a.Text))
+}
+
+// argsLabel renders a leaf test as written: the head followed by each
+// argument, bare symbols verbatim, strings as their decoded text in double
+// quotes without escaping.
+func argsLabel(head string, args []*sexp.Node) string {
+	var b strings.Builder
+	b.WriteString(head)
+	for _, a := range args {
+		b.WriteByte(' ')
+		if a.Kind == sexp.String {
+			b.WriteByte('"')
+			b.WriteString(a.Text)
+			b.WriteByte('"')
+		} else {
+			b.WriteString(a.Text)
+		}
+	}
+	return b.String()
+}