;; ==========================================================================
;; test-router.sx — Tests for client-side route matching & SX URL algebra
;;
;; Requires: test-framework.sx loaded first.
;; Modules tested: router.sx
;;
;; No additional platform functions needed — router.sx is pure.
;; ==========================================================================


;; --------------------------------------------------------------------------
;; split-path-segments
;; --------------------------------------------------------------------------

(defsuite "split-path-segments"
  (deftest "root path"
    (assert-equal (list) (split-path-segments "/")))

  (deftest "single segment"
    (assert-equal (list "docs") (split-path-segments "/docs")))

  (deftest "multiple segments"
    (assert-equal (list "docs" "hello") (split-path-segments "/docs/hello")))

  (deftest "trailing slash stripped"
    (assert-equal (list "docs") (split-path-segments "/docs/")))

  (deftest "deep path"
    (assert-equal (list "a" "b" "c" "d") (split-path-segments "/a/b/c/d"))))


;; --------------------------------------------------------------------------
;; parse-route-pattern
;; --------------------------------------------------------------------------

(defsuite "parse-route-pattern"
  (deftest "static pattern"
    (let ((segs (parse-route-pattern "/docs/intro")))
      (assert-length 2 segs)
      (assert-equal "literal" (get (first segs) "type"))
      (assert-equal "docs" (get (first segs) "value"))
      (assert-equal "literal" (get (nth segs 1) "type"))
      (assert-equal "intro" (get (nth segs 1) "value"))))

  (deftest "pattern with param"
    (let ((segs (parse-route-pattern "/docs/<slug>")))
      (assert-length 2 segs)
      (assert-equal "literal" (get (first segs) "type"))
      (assert-equal "docs" (get (first segs) "value"))
      (assert-equal "param" (get (nth segs 1) "type"))
      (assert-equal "slug" (get (nth segs 1) "value"))))

  (deftest "multiple params"
    (let ((segs (parse-route-pattern "/users/<uid>/posts/<pid>")))
      (assert-length 4 segs)
      (assert-equal "param" (get (nth segs 1) "type"))
      (assert-equal "uid" (get (nth segs 1) "value"))
      (assert-equal "param" (get (nth segs 3) "type"))
      (assert-equal "pid" (get (nth segs 3) "value"))))

  (deftest "root pattern"
    (assert-equal (list) (parse-route-pattern "/"))))


;; --------------------------------------------------------------------------
;; match-route
;; --------------------------------------------------------------------------

(defsuite "match-route"
  (deftest "exact match returns empty params"
    (let ((result (match-route "/docs/intro" "/docs/intro")))
      (assert-true (not (nil? result)))
      (assert-length 0 (keys result))))

  (deftest "param match extracts value"
    (let ((result (match-route "/docs/hello" "/docs/<slug>")))
      (assert-true (not (nil? result)))
      (assert-equal "hello" (get result "slug"))))

  (deftest "no match returns nil"
    (assert-nil (match-route "/docs/hello" "/essays/<slug>"))
    (assert-nil (match-route "/docs" "/docs/<slug>")))

  (deftest "segment count mismatch returns nil"
    (assert-nil (match-route "/a/b/c" "/a/<b>"))
    (assert-nil (match-route "/a" "/a/b")))

  (deftest "root matches root"
    (let ((result (match-route "/" "/")))
      (assert-true (not (nil? result)))))

  (deftest "multiple params extracted"
    (let ((result (match-route "/users/42/posts/99" "/users/<uid>/posts/<pid>")))
      (assert-true (not (nil? result)))
      (assert-equal "42" (get result "uid"))
      (assert-equal "99" (get result "pid")))))


;; --------------------------------------------------------------------------
;; find-matching-route
;; --------------------------------------------------------------------------

(defsuite "find-matching-route"
  (deftest "finds first matching route"
    (let ((routes (list
            {:pattern "/docs/" :parsed (parse-route-pattern "/docs/") :name "docs-index"}
            {:pattern "/docs/<slug>" :parsed (parse-route-pattern "/docs/<slug>") :name "docs-page"})))
      (let ((result (find-matching-route "/docs/hello" routes)))
        (assert-true (not (nil? result)))
        (assert-equal "docs-page" (get result "name"))
        (assert-equal "hello" (get (get result "params") "slug")))))

  (deftest "returns nil for no match"
    (let ((routes (list
            {:pattern "/docs/<slug>" :parsed (parse-route-pattern "/docs/<slug>") :name "docs-page"})))
      (assert-nil (find-matching-route "/essays/hello" routes))))

  (deftest "matches exact routes before param routes"
    (let ((routes (list
            {:pattern "/docs/" :parsed (parse-route-pattern "/docs/") :name "docs-index"}
            {:pattern "/docs/<slug>" :parsed (parse-route-pattern "/docs/<slug>") :name "docs-page"})))
      (let ((result (find-matching-route "/docs/" routes)))
        (assert-true (not (nil? result)))
        (assert-equal "docs-index" (get result "name")))))

  (deftest "propagates stream flag from route"
    (let ((routes (list
            {:pattern "/demo/streaming"
             :parsed (parse-route-pattern "/demo/streaming")
             :name "streaming-demo"
             :stream true
             :has-data true})))
      (let ((result (find-matching-route "/demo/streaming" routes)))
        (assert-true (not (nil? result)))
        (assert-equal true (get result "stream"))
        (assert-equal true (get result "has-data")))))

  (deftest "non-streaming route has no stream flag"
    (let ((routes (list
            {:pattern "/about"
             :parsed (parse-route-pattern "/about")
             :name "about"
             :has-data false})))
      (let ((result (find-matching-route "/about" routes)))
        (assert-true (not (nil? result)))
        (assert-nil (get result "stream"))))))


;; --------------------------------------------------------------------------
;; sx-url-to-path — SX expression URL → old-style path
;; --------------------------------------------------------------------------

(defsuite "sx-url-to-path"
  (deftest "simple two-level"
    (assert-equal "/language/docs/introduction"
      (sx-url-to-path "/(language.(doc.introduction))")))

  (deftest "deep nesting"
    (assert-equal "/geography/hypermedia/reference/attributes"
      (sx-url-to-path "/(geography.(hypermedia.(reference.attributes)))")))

  (deftest "section index"
    (assert-equal "/language"
      (sx-url-to-path "/(language)")))

  (deftest "function name mapping — doc to docs"
    (assert-equal "/language/docs/getting-started"
      (sx-url-to-path "/(language.(doc.getting-started))")))

  (deftest "function name mapping — spec to specs"
    (assert-equal "/language/specs/core"
      (sx-url-to-path "/(language.(spec.core))")))

  (deftest "function name mapping — example to examples"
    (assert-equal "/geography/hypermedia/examples/click-to-load"
      (sx-url-to-path "/(geography.(hypermedia.(example.click-to-load)))")))

  (deftest "function name mapping — essay to essays"
    (assert-equal "/etc/essays/sx-sucks"
      (sx-url-to-path "/(etc.(essay.sx-sucks))")))

  (deftest "function name mapping — plan to plans"
    (assert-equal "/etc/plans/spec-explorer"
      (sx-url-to-path "/(etc.(plan.spec-explorer))")))

  (deftest "function name mapping — test to testing"
    (assert-equal "/language/testing/eval"
      (sx-url-to-path "/(language.(test.eval))")))

  (deftest "function name mapping — bootstrapper to bootstrappers"
    (assert-equal "/language/bootstrappers/python"
      (sx-url-to-path "/(language.(bootstrapper.python))")))

  (deftest "function name mapping — protocol to protocols"
    (assert-equal "/applications/protocols/wire-format"
      (sx-url-to-path "/(applications.(protocol.wire-format))")))

  (deftest "function name mapping — reference-detail to reference"
    (assert-equal "/geography/hypermedia/reference/attributes"
      (sx-url-to-path "/(geography.(hypermedia.(reference-detail.attributes)))")))

  (deftest "non-SX URL returns nil"
    (assert-nil (sx-url-to-path "/language/docs/introduction"))
    (assert-nil (sx-url-to-path "https://example.com"))))


;; --------------------------------------------------------------------------
;; find-matching-route with SX URLs
;; --------------------------------------------------------------------------

(defsuite "find-matching-route-sx-urls"
  (deftest "SX URL auto-converts for matching"
    (let ((routes (list
            {:pattern "/language/docs/<slug>"
             :parsed (parse-route-pattern "/language/docs/<slug>")
             :name "docs-page"})))
      (let ((result (find-matching-route "/(language.(doc.introduction))" routes)))
        (assert-true (not (nil? result)))
        (assert-equal "docs-page" (get result "name"))
        (assert-equal "introduction" (get (get result "params") "slug"))))))


;; ==========================================================================
;; SX URL Resolution — Structural Navigation
;; ==========================================================================

(defsuite "relative-sx-url?"
  (deftest "paren-form relative"
    (assert-true (relative-sx-url? "(.slug)"))
    (assert-true (relative-sx-url? "(..)"))
    (assert-true (relative-sx-url? "(..reactive.demo)")))

  (deftest "bare-dot relative"
    (assert-true (relative-sx-url? ".slug"))
    (assert-true (relative-sx-url? ".."))
    (assert-true (relative-sx-url? "..."))
    (assert-true (relative-sx-url? ".:page.4")))

  (deftest "absolute URLs are not relative"
    (assert-false (relative-sx-url? "/(language.(doc.intro))"))
    (assert-false (relative-sx-url? "/"))
    (assert-false (relative-sx-url? "/language/docs/intro")))

  (deftest "special form URLs are not relative"
    (assert-false (relative-sx-url? "/(!source.(~essay))"))))


;; --------------------------------------------------------------------------
;; Structural: append at current level (1 dot)
;; --------------------------------------------------------------------------

(defsuite "resolve-relative-url: append (.slug)"
  (deftest "append to deep URL"
    (assert-equal "/(geography.(hypermedia.(example.progress-bar)))"
      (resolve-relative-url
        "/(geography.(hypermedia.(example)))"
        "(.progress-bar)")))

  (deftest "append to single-level URL"
    (assert-equal "/(language.intro)"
      (resolve-relative-url "/(language)" "(.intro)")))

  (deftest "append with multi-token body"
    (assert-equal "/(geography.(hypermedia.(example.progress-bar.v2)))"
      (resolve-relative-url
        "/(geography.(hypermedia.(example)))"
        "(.progress-bar.v2)")))

  (deftest "bare-dot shorthand"
    (assert-equal "/(geography.(hypermedia.(example.progress-bar)))"
      (resolve-relative-url
        "/(geography.(hypermedia.(example)))"
        ".progress-bar"))))


;; --------------------------------------------------------------------------
;; Structural: go up one level (2 dots)
;; --------------------------------------------------------------------------

(defsuite "resolve-relative-url: up one (..slug)"
  (deftest "sibling call"
    (assert-equal "/(geography.(hypermedia.(reactive.demo)))"
      (resolve-relative-url
        "/(geography.(hypermedia.(example)))"
        "(..reactive.demo)")))

  (deftest "just go up — no new content"
    (assert-equal "/(geography.(hypermedia))"
      (resolve-relative-url
        "/(geography.(hypermedia.(example)))"
        "(..)")))

  (deftest "bare-dot shorthand for up"
    (assert-equal "/(geography.(hypermedia))"
      (resolve-relative-url
        "/(geography.(hypermedia.(example)))"
        "..")))

  (deftest "up from two-level URL"
    (assert-equal "/(language)"
      (resolve-relative-url "/(language.(doc))" "(..)")))

  (deftest "up from single-level pops to root"
    (assert-equal "/"
      (resolve-relative-url "/(language)" "(..)"))))


;; --------------------------------------------------------------------------
;; Structural: go up two levels (3 dots)
;; --------------------------------------------------------------------------

(defsuite "resolve-relative-url: up two (...slug)"
  (deftest "up two and push"
    (assert-equal "/(geography.(marshes))"
      (resolve-relative-url
        "/(geography.(hypermedia.(example)))"
        "(...marshes)")))

  (deftest "just up two — no content"
    (assert-equal "/(geography)"
      (resolve-relative-url
        "/(geography.(hypermedia.(example)))"
        "(...)")))

  (deftest "bare-dot shorthand for up two"
    (assert-equal "/(geography)"
      (resolve-relative-url
        "/(geography.(hypermedia.(example)))"
        "...")))

  (deftest "up two from two-level pops to root"
    (assert-equal "/"
      (resolve-relative-url "/(language.(doc))" "(...)")))

  (deftest "up two and push from deep URL"
    ;; 4-level URL, ... = 3 dots = pop 2 levels → at hypermedia level
    (assert-equal "/(geography.(hypermedia.(reactive.demo)))"
      (resolve-relative-url
        "/(geography.(hypermedia.(reference.(attributes))))"
        "(...reactive.demo)"))))


;; --------------------------------------------------------------------------
;; Structural: up N levels (N+1 dots)
;; --------------------------------------------------------------------------

(defsuite "resolve-relative-url: up N"
  (deftest "up three levels (4 dots) from 4-level URL"
    ;; 4-level URL, .... = 4 dots = pop 3 levels → at geography level
    (assert-equal "/(geography)"
      (resolve-relative-url
        "/(geography.(hypermedia.(reference.(attributes))))"
        "(....)")))

  (deftest "up three and push from 4-level URL"
    ;; 4 dots = pop 3 → at geography, then push new-section
    (assert-equal "/(geography.(new-section))"
      (resolve-relative-url
        "/(geography.(hypermedia.(reference.(attributes))))"
        "(....new-section)")))

  (deftest "up four levels (5 dots) pops to root"
    (assert-equal "/"
      (resolve-relative-url
        "/(geography.(hypermedia.(reference.(attributes))))"
        "(.....)"))))


;; --------------------------------------------------------------------------
;; Structural: current (1 dot, no body) = no-op
;; --------------------------------------------------------------------------

(defsuite "resolve-relative-url: current level no-op"
  (deftest "dot with no body is identity"
    ;; (.):  dots=1, body="" → no positional, no keywords → current unchanged
    (assert-equal "/(language.(doc.intro))"
      (resolve-relative-url "/(language.(doc.intro))" "(.)")))

  (deftest "bare dot shorthand"
    (assert-equal "/(language.(doc.intro))"
      (resolve-relative-url "/(language.(doc.intro))" "."))))


;; ==========================================================================
;; SX URL Resolution — Keyword Operations
;; ==========================================================================

;; --------------------------------------------------------------------------
;; Keyword set: absolute value
;; --------------------------------------------------------------------------

(defsuite "resolve-relative-url: keyword set"
  (deftest "set keyword on URL without keywords"
    (assert-equal "/(language.(spec.(explore.signals.:page.4)))"
      (resolve-relative-url
        "/(language.(spec.(explore.signals)))"
        "(.:page.4)")))

  (deftest "replace existing keyword"
    (assert-equal "/(language.(spec.(explore.signals.:page.4)))"
      (resolve-relative-url
        "/(language.(spec.(explore.signals.:page.3)))"
        "(.:page.4)")))

  (deftest "set keyword with bare-dot shorthand"
    (assert-equal "/(language.(spec.(explore.signals.:page.4)))"
      (resolve-relative-url
        "/(language.(spec.(explore.signals.:page.3)))"
        ".:page.4")))

  (deftest "set keyword on single-level URL"
    (assert-equal "/(language.:page.1)"
      (resolve-relative-url "/(language)" "(.:page.1)")))

  (deftest "set multiple keywords"
    (assert-equal "/(language.(spec.(explore.signals.:page.4.:section.batch)))"
      (resolve-relative-url
        "/(language.(spec.(explore.signals.:page.3)))"
        "(.:page.4.:section.batch)")))

  (deftest "add new keyword preserving existing"
    (assert-equal "/(language.(spec.(explore.signals.:page.3.:section.batch)))"
      (resolve-relative-url
        "/(language.(spec.(explore.signals.:page.3)))"
        "(.:section.batch)"))))


;; --------------------------------------------------------------------------
;; Keyword delta: +N / -N
;; --------------------------------------------------------------------------

(defsuite "resolve-relative-url: keyword delta"
  (deftest "increment by 1"
    (assert-equal "/(language.(spec.(explore.signals.:page.4)))"
      (resolve-relative-url
        "/(language.(spec.(explore.signals.:page.3)))"
        "(.:page.+1)")))

  (deftest "decrement by 1"
    (assert-equal "/(language.(spec.(explore.signals.:page.2)))"
      (resolve-relative-url
        "/(language.(spec.(explore.signals.:page.3)))"
        "(.:page.-1)")))

  (deftest "increment by larger amount"
    (assert-equal "/(language.(spec.(explore.signals.:page.13)))"
      (resolve-relative-url
        "/(language.(spec.(explore.signals.:page.3)))"
        "(.:page.+10)")))

  (deftest "delta with bare-dot shorthand"
    (assert-equal "/(language.(spec.(explore.signals.:page.4)))"
      (resolve-relative-url
        "/(language.(spec.(explore.signals.:page.3)))"
        ".:page.+1")))

  (deftest "delta on missing keyword uses literal"
    ;; If :page doesn't exist, +1 is used as-is (not numeric delta)
    (assert-equal "/(language.(spec.(explore.signals.:page.+1)))"
      (resolve-relative-url
        "/(language.(spec.(explore.signals)))"
        "(.:page.+1)"))))


;; --------------------------------------------------------------------------
;; Composed: structural + keyword
;; --------------------------------------------------------------------------

(defsuite "resolve-relative-url: composed structural + keyword"
  (deftest "append slug + set keyword"
    (assert-equal "/(language.(spec.(explore.signals.batch.:page.1)))"
      (resolve-relative-url
        "/(language.(spec.(explore.signals)))"
        "(.batch.:page.1)")))

  (deftest "sibling + set keyword"
    (assert-equal "/(language.(spec.(eval.:page.1)))"
      (resolve-relative-url
        "/(language.(spec.(explore.signals.:page.3)))"
        "(..eval.:page.1)")))

  (deftest "up two + set keyword"
    (assert-equal "/(geography.(reactive.demo.:page.1))"
      (resolve-relative-url
        "/(geography.(hypermedia.(example.progress-bar)))"
        "(...reactive.demo.:page.1)")))

  (deftest "bare-dot composed"
    (assert-equal "/(language.(spec.(eval.:page.1)))"
      (resolve-relative-url
        "/(language.(spec.(explore.signals.:page.3)))"
        "..eval.:page.1"))))


;; ==========================================================================
;; SX URL Parsing — parse-sx-url
;; ==========================================================================

(defsuite "parse-sx-url"
  (deftest "home URL"
    (let ((parsed (parse-sx-url "/")))
      (assert-equal "home" (get parsed "type"))
      (assert-equal "/" (get parsed "raw"))))

  (deftest "absolute SX URL"
    (let ((parsed (parse-sx-url "/(language.(doc.intro))")))
      (assert-equal "absolute" (get parsed "type"))))

  (deftest "relative paren-form"
    (let ((parsed (parse-sx-url "(.slug)")))
      (assert-equal "relative" (get parsed "type"))))

  (deftest "relative bare-dot"
    (let ((parsed (parse-sx-url ".slug")))
      (assert-equal "relative" (get parsed "type"))))

  (deftest "relative double-dot"
    (let ((parsed (parse-sx-url "..")))
      (assert-equal "relative" (get parsed "type"))))

  (deftest "direct component"
    (let ((parsed (parse-sx-url "/(~essay-sx-sucks)")))
      (assert-equal "direct-component" (get parsed "type"))
      (assert-equal "~essay-sx-sucks" (get parsed "name"))))

  (deftest "old-style path"
    (let ((parsed (parse-sx-url "/language/docs/intro")))
      (assert-equal "path" (get parsed "type")))))


;; ==========================================================================
;; URL Special Forms (! prefix)
;; ==========================================================================

(defsuite "url-special-form?"
  (deftest "known special forms"
    (assert-true (url-special-form? "!source"))
    (assert-true (url-special-form? "!inspect"))
    (assert-true (url-special-form? "!diff"))
    (assert-true (url-special-form? "!search"))
    (assert-true (url-special-form? "!raw"))
    (assert-true (url-special-form? "!json")))

  (deftest "unknown bang-prefix is not a special form"
    (assert-false (url-special-form? "!unknown"))
    (assert-false (url-special-form? "!foo")))

  (deftest "non-bang names are not special forms"
    (assert-false (url-special-form? "source"))
    (assert-false (url-special-form? "language"))
    (assert-false (url-special-form? "~essay"))))


(defsuite "parse-sx-url: special forms"
  (deftest "source special form"
    (let ((parsed (parse-sx-url "/(!source.(~essay-sx-sucks))")))
      (assert-equal "special-form" (get parsed "type"))
      (assert-equal "!source" (get parsed "form"))
      (assert-equal "(~essay-sx-sucks)" (get parsed "inner"))))

  (deftest "inspect special form"
    (let ((parsed (parse-sx-url "/(!inspect.(language.(doc.primitives)))")))
      (assert-equal "special-form" (get parsed "type"))
      (assert-equal "!inspect" (get parsed "form"))
      (assert-equal "(language.(doc.primitives))" (get parsed "inner"))))

  (deftest "diff special form with two args"
    (let ((parsed (parse-sx-url "/(!diff.(language.(spec.signals)).(language.(spec.eval)))")))
      (assert-equal "special-form" (get parsed "type"))
      (assert-equal "!diff" (get parsed "form"))
      (assert-equal "(language.(spec.signals)).(language.(spec.eval))" (get parsed "inner"))))

  (deftest "raw special form"
    (let ((parsed (parse-sx-url "/(!raw.(~some-component))")))
      (assert-equal "special-form" (get parsed "type"))
      (assert-equal "!raw" (get parsed "form"))
      (assert-equal "(~some-component)" (get parsed "inner"))))

  (deftest "json special form"
    (let ((parsed (parse-sx-url "/(!json.(language.(doc.primitives)))")))
      (assert-equal "special-form" (get parsed "type"))
      (assert-equal "!json" (get parsed "form"))
      (assert-equal "(language.(doc.primitives))" (get parsed "inner")))))


(defsuite "url-special-form-name"
  (deftest "extracts form name"
    (assert-equal "!source"
      (url-special-form-name "/(!source.(~essay))")))

  (deftest "returns nil for non-special-form"
    (assert-nil (url-special-form-name "/(language.(doc.intro))"))
    (assert-nil (url-special-form-name "/"))
    (assert-nil (url-special-form-name "(.slug)"))))


(defsuite "url-special-form-inner"
  (deftest "extracts inner expression"
    (assert-equal "(~essay)"
      (url-special-form-inner "/(!source.(~essay))")))

  (deftest "extracts multi-arg inner"
    (assert-equal "(a).(b)"
      (url-special-form-inner "/(!diff.(a).(b))")))

  (deftest "returns nil for non-special-form"
    (assert-nil (url-special-form-inner "/(language.(doc.intro))"))))


;; ==========================================================================
;; Internal helpers — additional edge cases
;; ==========================================================================

(defsuite "internal: _pop-sx-url-level"
  (deftest "pop three-level"
    (assert-equal "/(a.(b))"
      (_pop-sx-url-level "/(a.(b.(c)))")))

  (deftest "pop two-level"
    (assert-equal "/(a)"
      (_pop-sx-url-level "/(a.(b))")))

  (deftest "pop single-level to root"
    (assert-equal "/"
      (_pop-sx-url-level "/(a)")))

  (deftest "pop root stays root"
    (assert-equal "/"
      (_pop-sx-url-level "/"))))

(defsuite "internal: _extract-innermost"
  (deftest "single-level URL"
    (let ((parts (_extract-innermost "/(language)")))
      (assert-equal "/(" (get parts "before"))
      (assert-equal "language" (get parts "content"))
      (assert-equal ")" (get parts "suffix"))))

  (deftest "two-level URL"
    (let ((parts (_extract-innermost "/(language.(doc.intro))")))
      (assert-equal "/(language.(" (get parts "before"))
      (assert-equal "doc.intro" (get parts "content"))
      (assert-equal "))" (get parts "suffix"))))

  (deftest "three-level URL with keywords"
    (let ((parts (_extract-innermost "/(a.(b.(c.d.:page.3)))")))
      (assert-equal "/(a.(b.(" (get parts "before"))
      (assert-equal "c.d.:page.3" (get parts "content"))
      (assert-equal ")))" (get parts "suffix")))))

(defsuite "internal: _find-keyword-value"
  (deftest "finds keyword"
    (assert-equal "3"
      (_find-keyword-value "explore.signals.:page.3" ":page")))

  (deftest "returns nil when not found"
    (assert-nil (_find-keyword-value "explore.signals" ":page")))

  (deftest "finds among multiple keywords"
    (assert-equal "batch"
      (_find-keyword-value "explore.signals.:page.3.:section.batch" ":section"))))

(defsuite "internal: _set-keyword-in-content"
  (deftest "replace existing"
    (assert-equal "a.b.:page.4"
      (_set-keyword-in-content "a.b.:page.3" ":page" "4")))

  (deftest "append when missing"
    (assert-equal "a.b.:page.1"
      (_set-keyword-in-content "a.b" ":page" "1")))

  (deftest "replace with multiple keywords present"
    (assert-equal "a.:page.4.:section.batch"
      (_set-keyword-in-content "a.:page.3.:section.batch" ":page" "4"))))

(defsuite "internal: _is-delta-value?"
  (deftest "positive delta"
    (assert-true (_is-delta-value? "+1"))
    (assert-true (_is-delta-value? "+10")))

  (deftest "negative delta"
    (assert-true (_is-delta-value? "-1"))
    (assert-true (_is-delta-value? "-10")))

  (deftest "bare minus is not delta"
    (assert-false (_is-delta-value? "-")))

  (deftest "bare plus is not delta"
    (assert-false (_is-delta-value? "+")))

  (deftest "plain number is not delta"
    (assert-false (_is-delta-value? "3"))
    (assert-false (_is-delta-value? "0")))

  (deftest "empty string is not delta"
    (assert-false (_is-delta-value? ""))))

(defsuite "internal: _apply-delta"
  (deftest "increment"
    (assert-equal "4" (_apply-delta "3" "+1")))

  (deftest "decrement"
    (assert-equal "2" (_apply-delta "3" "-1")))

  (deftest "large increment"
    (assert-equal "13" (_apply-delta "3" "+10")))

  (deftest "non-numeric current falls back"
    (assert-equal "+1" (_apply-delta "abc" "+1"))))