export alias "h. get" = h. request get
export alias "h. post" = h. request post

alias ? = if ($in | is-not-empty) { $in }
alias ?? = ? else { return }

def and-then [ next: closure --else: closure ] {
    if ($in | is-not-empty) { do $next } else {
        do $else
    }
}

export def store-addr [] {
    $env | get XS_ADDR? | ? else { "./store" }
}

# update to use (store-addr) and the xs cli
def _cat [options: record] {
    let params = [
        (if ($options | get follow? | default false) { "--follow" })
        (if ($options | get tail? | default false) { "--tail" })

        (if $options.last_id? != null { ["--last-id" $options.last_id] })

        (if $options.limit? != null { ["--limit" $options.limit] })
        (if $options.pulse? != null { ["--pulse" $options.pulse] })
    ] | compact | flatten

    xs cat (store-addr) ...$params | lines | each { |x| $x | from json }
}

export def .cat [
    --follow (-f)       # long poll for new events
    --pulse (-p): int   # specifies the interval (in milliseconds) to receive a synthetic "xs.pulse" event
    --tail (-t)         # begin long after the end of the stream
    --last-id (-l): string
    --limit: int
] {
    _cat {follow: $follow pulse: $pulse tail: $tail last_id: $last_id limit: $limit}
}

def read_hash [hash?: any] {
    match ($hash | describe -d | get type) {
        "string" => $hash
        "record" => ($hash | get hash?)
        _ => null
    }
}

# .step: Process events from a topic, using a subtopic as a cursor for the last processed event.
#
# Parameters:
#   handler: closure     - Processes each event. Return null to continue, non-null to stop.
#   proto_topic: string  - Main topic to process events from. Cursor stored in "{proto_topic}.last-id".
#   --follow (-f)        - Optional. Long poll for new events.
#
# Behavior:
# - Processes events from proto_topic, using "{proto_topic}.last-id" as a cursor.
# - Calls handler for each event, skips events matching the cursor subtopic.
# - Updates cursor after processing each event.
# - Continues until handler returns non-null or no more events (unless --follow is set).
#
# Returns:
# - {in: $frame, out: $res} if handler returns non-null, where $frame is the input event
#   and $res is the handler's output. Returns null if all events processed or none available.
#
# Note: something doesn't feel right about using the stream to track last
# processed id, which requires us to skip our own emissions
export def .step [
    handler: closure
    proto_topic: string
    --follow (-f)       # long poll for new events
] {
    let topic = $"($proto_topic).last-id"


    mut prev = .head $topic | and-then { {
        last_id: ($in.meta.last_id)
    } } --else { {} }

    loop {
        let frame = _cat ($prev | insert follow $follow | insert limit 1) | try { first }
        if $frame == null { return }

        $prev.last_id = $frame.id
        if $frame.topic == $topic {
            continue
        }

        let res = $frame | do $handler
        if $res != null {
            return {in: $frame out: $res}
        }

        .append $topic --meta {last_id: $prev.last_id}
    }
}

export def .cas [hash?: any] {
    let alt = $in
    let hash = read_hash (if $hash != null { $hash } else { $alt })
    if $hash == null { return }
    xs cas (store-addr) $hash
}

export def .get [id: string] {
    xs get (store-addr) $id | from json
}

export def .head [topic: string] {
    xs head (store-addr) $topic | from json
}

# Append an event to the stream
export def .append [
    topic: string  # The topic to append the event to
    --meta: record  # Optional metadata to include with the event, provided as a record
    --ttl: string  # Optional Time-To-Live for the event. Supported formats:
                   #   - "forever": The event is kept indefinitely.
                   #   - "ephemeral": The event is not stored; only active subscribers can see it.
                   #   - "time:<milliseconds>": The event is kept for a custom duration in milliseconds.
                   #   - "head:<n>": Retains only the last n events for the topic (n must be >= 1).
] {
    xs append (store-addr) $topic ...([
        (if $meta != null { ["--meta" ($meta | to json -r)] })
        (if $ttl != null { ["--ttl" $ttl] })
    ] | compact | flatten) | from json
}

export def .remove [id: string] {
    xs remove (store-addr) $id
}

export alias .rm = .remove

export def .process [id: string] {
    let sp = (metadata $in).span
    let script = $in
    let content = match ($script | describe -d | get type) {
        "string" => $script
        "closure" => {view source $script}
        _ => {return (error make {
            msg: "script should either be a string or closure"
            label: {
                text: "script input"
                span: $sp
            }
        })}
    }
    $content | xs process (store-addr) $id
}

# show the status of running tasks TBD
export def .tasks [] {
    .cat
}

export def .dump [path: string] {
    if ($path | path exists) {
        print "path exists"
        return
    }
    mkdir ($path | path join "cas")

    xs cat (store-addr) | save ($path | path join "frames.jsonl")

    open ($path | path join "frames.jsonl") | lines | each { from json | get hash } | uniq | each {|hash|
        # if ($hash | is-empty) { return }
        let hash_64 = $hash | encode base64
        let out_path = $"($path)/cas/($hash_64)"
        print $out_path
        .cas $hash | save $out_path
    }
}

export def .load [path: string] {
    glob ([$path "cas"] | path join "*") | each {|x|
        let want = ($x | path basename | decode base64 | decode)
        let got = cat $x | xs cas-post (store-addr)
        if $got != $want {
            return (error make {
                msg: $"hash mismatch got=($got) want=($want)",
            })
        }
        $got
    }

    open ($path | path join "frames.jsonl") | lines | each { xs import (store-addr) }
}

export def .test [] {
    use std assert;
    let cases = [
        [
            "sha256-k//MXqRXKqeE+7S7SkKSbpU3dWrxwzh/iR6v683XTyE="
            "sha256-k//MXqRXKqeE+7S7SkKSbpU3dWrxwzh/iR6v683XTyE="
        ]
        [
            {hash: "sha256-k//MXqRXKqeE+7S7SkKSbpU3dWrxwzh/iR6v683XTyE="}
            "sha256-k//MXqRXKqeE+7S7SkKSbpU3dWrxwzh/iR6v683XTyE="
        ]
        [ null null ]
        [ {goo: 123} null ]
    ]

    for case in $cases {
        assert equal (read_hash $case.0) $case.1
    }
}