observer.aro

(* ============================================================
   observer.aro – Render terminal UI on every UIState change.

   Fan-out pattern:
     ui-state-repository Observer → computes style, emits Render event with mode + style
     Render Handler where <event: mode> == "setup"    – first-run token entry
     Render Handler where <event: mode> == "compose"  – new post dialog
     Render Handler where <event: mode> == "timeline" – scrollable post list

   Variable naming constraints:
   - No <is-*>  (is = keyword)
   - No <*-at>  (at = preposition)
   ============================================================ *)

(* ---- Dispatch: compute style once, emit Render event with mode + style ---- *)

(Dispatch UI Render: ui-state-repository Observer) {
    Extract the <state: UIState> from the <event: newValue>.
    Extract the <mode>            from the <state: mode>.
    Compute the <sep-width>   from (<terminal: columns>).
    Compute the <separator>   from "─" * <sep-width>.
    Compute the <input-width> from (<terminal: columns>) - 4.
    Create the <style: TerminalStyles> with {
        separatorLine:   <separator>,
        inputWidth:      <input-width>,
        reset:           "\u{001B}[0m",
        muted:           "\u{001B}[2m",
        heading:         "\u{001B}[1m\u{001B}[97m",
        prompt:          "\u{001B}[36m",
        cursor:          "\u{001B}[32m",
        counter:         "\u{001B}[33m",
        authorName:      "\u{001B}[1m",
        username:        "\u{001B}[36m",
        cursorIndicator: "\u{001B}[32m"
    }.
    Emit a <Render: event>        with { mode: <mode>, style: <style> }.
    Return an <OK: status> for the <dispatch>.
}

(* ── Setup screen ── *)

(Render Setup: Render Handler) where <event: mode> == "setup" {
    Retrieve the <state: UIState> from the <ui-state-repository> where <key> is "main".
    Extract the <style: TerminalStyles> from the <event: style>.

    Extract the <compose-text>           from the <state: composeText>.
    Compute the <step-requests-instance> from (<state: setupStep>) == "instance".
    match <step-requests-instance> {
        case true  { Create the <setup-prompt> with "Enter your Mastodon instance URL (e.g. https://mastodon.social):". }
        case false { Create the <setup-prompt> with "Enter your access token:". }
    }
    Transform the <display> from the <template: setup.screen>.
    Render the <display> to the <console>.
    Return an <OK: status> for the <render>.
}

(* ── Compose screen ── *)

(Render Compose: Render Handler) where <event: mode> == "compose" {
    Retrieve the <state: UIState> from the <ui-state-repository> where <key> is "main".
    Extract the <style: TerminalStyles> from the <event: style>.

    Extract the <compose-text>            from the <state: composeText>.
    Compute the <character-count: length> from <compose-text>.
    Compute the <chars-remaining>         from 500 - <character-count>.
    Transform the <display> from the <template: compose.screen>.
    Render the <display> to the <console>.
    Return an <OK: status> for the <render>.
}

(* ── Reply screen ── *)

(Render Reply: Render Handler) where <event: mode> == "reply" {
    Retrieve the <state: UIState> from the <ui-state-repository> where <key> is "main".
    Extract the <style: TerminalStyles> from the <event: style>.

    (* Reduce visible slots by 5 rows to fit inline reply box *)
    Compute the <panel-height>  from (<terminal: rows>) - 8.
    Compute the <visible-count> from <panel-height> / 3.

    Compute the <account-column-width> from (<terminal: columns>) - 42.
    Compute the <content-column-width> from (<terminal: columns>) - 4.
    Compute the <post-separator-width> from (<terminal: columns>) - 2.
    Compute the <post-separator>       from "─" * <post-separator-width>.

    Delete the <previous-slots>       from the <visible-slot-repository>.
    Delete the <previous-wrap-states> from the <wrap-state-repository>.

    for <slot-index> from 0 to <visible-count> {
        Compute the <post-index> from <slot-index> + (<state: selection>).

        Retrieve the <post> from the <post-repository>
            where <key> = <post-index>
            default { key: -1, acct: "", displayName: "", content: "", createdAt: "", boosterAcct: "", boosted: "", favourited: "" }.

        Extract the <post-account>      from the <post: acct>.
        Extract the <post-display-name> from the <post: displayName>.
        Extract the <post-content>      from the <post: content>.
        Extract the <post-date>         from the <post: createdAt>.
        Extract the <post-booster>      from the <post: boosterAcct>.

        Compute the <this-slot-selected> from <slot-index> == (<state: cursor>).
        match <this-slot-selected> {
            case true  { Create the <cursor-marker> with "▶". }
            case false { Create the <cursor-marker> with " ". }
        }

        Compute the <account-text: clip>        from <post-account>      with <account-column-width>.
        Compute the <author-display-text: clip>  from <post-display-name> with 18.
        Compute the <date-display-text: clip>    from <post-date>         with 16.

        Split the <content-words> from <post-content> by /\s/.
        Create the <initial-wrap-state> with { key: <slot-index>, curLine: "", result: "" }.
        Store the <initial-wrap-state> into the <wrap-state-repository>.

        for each <word> in <content-words> {
            Compute the <word-character-count: length> from <word>.
            Compute the <word-has-no-text>             from <word-character-count> == 0.
            match <word-has-no-text> {
                case true  { }
                case false {
                    Retrieve the <wrap-state>     from the <wrap-state-repository> where <key> = <slot-index>.
                    Extract the <current-line>    from the <wrap-state: curLine>.
                    Extract the <completed-lines> from the <wrap-state: result>.

                    Compute the <current-line-length: length> from <current-line>.
                    Compute the <current-line-has-no-words>  from <current-line-length> == 0.
                    match <current-line-has-no-words> {
                        case true  { Create the <projected-length> with <word-character-count>. }
                        case false { Compute the <projected-length> from <current-line-length> + <word-character-count> + 1. }
                    }

                    Compute the <word-fits-current-line> from <projected-length> <= <content-column-width>.
                    match <word-fits-current-line> {
                        case true {
                            match <current-line-has-no-words> {
                                case true  { Create the <line-extended> with <word>. }
                                case false { Compute the <line-extended> from <current-line> ++ " " ++ <word>. }
                            }
                            Update the <wrap-state: curLine> with <line-extended>.
                            Store the <wrap-state> into the <wrap-state-repository>.
                        }
                        case false {
                            Compute the <no-completed-lines-yet> from <completed-lines> == "".
                            match <no-completed-lines-yet> {
                                case true  { Create the <completed-lines-extended> with <current-line>. }
                                case false { Compute the <completed-lines-extended> from <completed-lines> ++ "\u{000A}  " ++ <current-line>. }
                            }
                            Update the <wrap-state: result>  with <completed-lines-extended>.
                            Update the <wrap-state: curLine> with <word>.
                            Store the <wrap-state> into the <wrap-state-repository>.
                        }
                    }
                }
            }
        }

        Retrieve the <final-wrap-state>   from the <wrap-state-repository> where <key> = <slot-index>.
        Extract the <last-partial-line>   from the <final-wrap-state: curLine>.
        Extract the <all-completed-lines> from the <final-wrap-state: result>.
        Compute the <content-fits-one-line> from <all-completed-lines> == "".
        match <content-fits-one-line> {
            case true  { Create the <wrapped-content> with <last-partial-line>. }
            case false { Compute the <wrapped-content> from <all-completed-lines> ++ "\u{000A}  " ++ <last-partial-line>. }
        }

        Compute the <booster-len: length> from <post-booster>.
        Compute the <has-booster>         from <booster-len> > 0.
        match <has-booster> {
            case true  { Compute the <booster-label> from "\u{001B}[2m ↻ \u{001B}[0m\u{001B}[36m@" ++ <post-booster> ++ "\u{001B}[0m". }
            case false { Create the <booster-label> with "". }
        }

        Extract the <post-boosted>  from the <post: boosted>.
        Compute the <was-boosted>   from <post-boosted> == "true".
        match <was-boosted> {
            case true  { Create the <boost-marker> with " 🚀". }
            case false { Create the <boost-marker> with "". }
        }

        Extract the <post-favourited> from the <post: favourited>.
        Compute the <was-favourited>  from <post-favourited> == "true".
        match <was-favourited> {
            case true  { Create the <fav-marker> with " ❤️". }
            case false { Create the <fav-marker> with "". }
        }

        Create the <slot: Slot> with { key: <slot-index>, marker: <cursor-marker>, acct: <account-text>, name: <author-display-text>, content: <wrapped-content>, date: <date-display-text>, booster: <booster-label>, boostMarker: <boost-marker>, favMarker: <fav-marker>, sep: <post-separator> }.
        Store the <slot> into the <visible-slot-repository>.
    }

    (* ── Split slots into pre-cursor and post-cursor for inline reply prompt ── *)
    Extract the <cursor-pos>  from the <state: cursor>.
    Compute the <post-start>  from <cursor-pos> + 1.

    Delete the <prev-pre-slots>  from the <pre-slot-repository>.
    Delete the <prev-post-slots> from the <post-slot-repository>.

    for <pre-idx> from 0 to <post-start> {
        Retrieve the <pre-slot> from the <visible-slot-repository> where <key> = <pre-idx>.
        Store the <pre-slot> into the <pre-slot-repository>.
    }

    Compute the <post-slots-exist> from <post-start> <= <visible-count>.
    match <post-slots-exist> {
        case true {
            for <post-idx> from <post-start> to <visible-count> {
                Retrieve the <post-slot> from the <visible-slot-repository> where <key> = <post-idx>.
                Store the <post-slot> into the <post-slot-repository>.
            }
        }
        case false { }
    }

    Retrieve the <pre-display-slots>  from the <pre-slot-repository>.
    Retrieve the <post-display-slots> from the <post-slot-repository>.

    Extract the <selection>   from the <state: selection>.
    Extract the <total-posts> from the <state: totalPosts>.

    Compute the <scroll-position-zero> from <selection> == 0.
    Compute the <cursor-position-zero> from (<state: cursor>) == 0.
    Compute the <viewing-post-top>     from <scroll-position-zero> AND <cursor-position-zero>.
    match <viewing-post-top> {
        case true  { Create the <auto-label> with "\u{001B}[34m (autoupdate)\u{001B}[0m". }
        case false { Create the <auto-label> with "". }
    }

    Extract the <compose-text>            from the <state: composeText>.
    Extract the <reply-acct>              from the <state: replyToAcct>.
    Compute the <character-count: length> from <compose-text>.

    Transform the <display> from the <template: reply.screen>.
    Render the <display> to the <console>.
    Return an <OK: status> for the <render>.
}

(* ── Timeline screen ── *)

(Render Timeline: Render Handler) where <event: mode> == "timeline" {
    Retrieve the <state: UIState> from the <ui-state-repository> where <key> is "main".
    Extract the <style: TerminalStyles> from the <event: style>.

    Compute the <panel-height>  from (<terminal: rows>) - 3.
    Compute the <visible-count> from <panel-height> / 3.

    Compute the <account-column-width> from (<terminal: columns>) - 42.
    Compute the <content-column-width> from (<terminal: columns>) - 4.
    Compute the <post-separator-width> from (<terminal: columns>) - 2.
    Compute the <post-separator>       from "─" * <post-separator-width>.

    Delete the <previous-slots>       from the <visible-slot-repository>.
    Delete the <previous-wrap-states> from the <wrap-state-repository>.

    for <slot-index> from 0 to <visible-count> {
        Compute the <post-index> from <slot-index> + (<state: selection>).

        Retrieve the <post> from the <post-repository>
            where <key> = <post-index>
            default { key: -1, acct: "", displayName: "", content: "", createdAt: "", boosterAcct: "", boosted: "", favourited: "" }.

        Extract the <post-account>      from the <post: acct>.
        Extract the <post-display-name> from the <post: displayName>.
        Extract the <post-content>      from the <post: content>.
        Extract the <post-date>         from the <post: createdAt>.
        Extract the <post-booster>      from the <post: boosterAcct>.

        Compute the <this-slot-selected> from <slot-index> == (<state: cursor>).
        match <this-slot-selected> {
            case true  { Create the <cursor-marker> with "▶". }
            case false { Create the <cursor-marker> with " ". }
        }

        Compute the <account-text: clip>        from <post-account>      with <account-column-width>.
        Compute the <author-display-text: clip>  from <post-display-name> with 18.
        Compute the <date-display-text: clip>    from <post-date>         with 16.

        (* ── Word-wrap post content into lines of content-column-width ── *)
        Split the <content-words> from <post-content> by /\s/.
        Create the <initial-wrap-state> with { key: <slot-index>, curLine: "", result: "" }.
        Store the <initial-wrap-state> into the <wrap-state-repository>.

        for each <word> in <content-words> {
            Compute the <word-character-count: length> from <word>.
            Compute the <word-has-no-text>             from <word-character-count> == 0.
            match <word-has-no-text> {
                case true  { }
                case false {
                    Retrieve the <wrap-state>     from the <wrap-state-repository> where <key> = <slot-index>.
                    Extract the <current-line>    from the <wrap-state: curLine>.
                    Extract the <completed-lines> from the <wrap-state: result>.

                    Compute the <current-line-length: length> from <current-line>.
                    Compute the <current-line-has-no-words>  from <current-line-length> == 0.
                    match <current-line-has-no-words> {
                        case true  { Create the <projected-length> with <word-character-count>. }
                        case false { Compute the <projected-length> from <current-line-length> + <word-character-count> + 1. }
                    }

                    Compute the <word-fits-current-line> from <projected-length> <= <content-column-width>.
                    match <word-fits-current-line> {
                        case true {
                            match <current-line-has-no-words> {
                                case true  { Create the <line-extended> with <word>. }
                                case false { Compute the <line-extended> from <current-line> ++ " " ++ <word>. }
                            }
                            Update the <wrap-state: curLine> with <line-extended>.
                            Store the <wrap-state> into the <wrap-state-repository>.
                        }
                        case false {
                            Compute the <no-completed-lines-yet> from <completed-lines> == "".
                            match <no-completed-lines-yet> {
                                case true  { Create the <completed-lines-extended> with <current-line>. }
                                case false { Compute the <completed-lines-extended> from <completed-lines> ++ "\u{000A}  " ++ <current-line>. }
                            }
                            Update the <wrap-state: result>  with <completed-lines-extended>.
                            Update the <wrap-state: curLine> with <word>.
                            Store the <wrap-state> into the <wrap-state-repository>.
                        }
                    }
                }
            }
        }

        Retrieve the <final-wrap-state>   from the <wrap-state-repository> where <key> = <slot-index>.
        Extract the <last-partial-line>   from the <final-wrap-state: curLine>.
        Extract the <all-completed-lines> from the <final-wrap-state: result>.
        Compute the <content-fits-one-line> from <all-completed-lines> == "".
        match <content-fits-one-line> {
            case true  { Create the <wrapped-content> with <last-partial-line>. }
            case false { Compute the <wrapped-content> from <all-completed-lines> ++ "\u{000A}  " ++ <last-partial-line>. }
        }
        (* ── End word-wrap ── *)

        (* ── Repost indicator ── *)
        Compute the <booster-len: length> from <post-booster>.
        Compute the <has-booster>         from <booster-len> > 0.
        match <has-booster> {
            case true  { Compute the <booster-label> from "\u{001B}[2m ↻ \u{001B}[0m\u{001B}[36m@" ++ <post-booster> ++ "\u{001B}[0m". }
            case false { Create the <booster-label> with "". }
        }

        Extract the <post-boosted>  from the <post: boosted>.
        Compute the <was-boosted>   from <post-boosted> == "true".
        match <was-boosted> {
            case true  { Create the <boost-marker> with " 🚀". }
            case false { Create the <boost-marker> with "". }
        }

        Extract the <post-favourited> from the <post: favourited>.
        Compute the <was-favourited>  from <post-favourited> == "true".
        match <was-favourited> {
            case true  { Create the <fav-marker> with " ❤️". }
            case false { Create the <fav-marker> with "". }
        }

        Create the <slot: Slot> with { key: <slot-index>, marker: <cursor-marker>, acct: <account-text>, name: <author-display-text>, content: <wrapped-content>, date: <date-display-text>, booster: <booster-label>, boostMarker: <boost-marker>, favMarker: <fav-marker>, sep: <post-separator> }.
        Store the <slot> into the <visible-slot-repository>.
    }

    Retrieve the <display-slots> from the <visible-slot-repository>.

    Extract the <selection>   from the <state: selection>.
    Extract the <total-posts> from the <state: totalPosts>.

    Compute the <scroll-position-zero> from <selection> == 0.
    Compute the <cursor-position-zero> from (<state: cursor>) == 0.
    Compute the <viewing-post-top>     from <scroll-position-zero> AND <cursor-position-zero>.
    match <viewing-post-top> {
        case true  { Create the <auto-label> with "\u{001B}[34m (autoupdate)\u{001B}[0m". }
        case false { Create the <auto-label> with "". }
    }

    Transform the <display> from the <template: timeline.screen>.
    Render the <display> to the <console>.
    Return an <OK: status> for the <render>.
}