"""Shared Grafana panel builders for the dashboard generators in this directory.

Hand-writing Grafana panel JSON at any volume invites subtle inconsistencies -- one
panel with a slightly different fieldConfig shape, a typo'd unit. Every panel here goes
through one code path per type, so they are structurally identical by construction.

Used by gen_zfs.py and gen_smart.py. Both are run as scripts from this directory, so a
plain `from panels import ...` resolves.
"""

DS = {"type": "prometheus", "uid": "prometheus"}

# Thresholds: green until the value reaches 1, then red. For "any of these is a problem"
# counters.
OK_BAD = {"mode": "absolute", "steps": [
    {"color": "green", "value": None},
    {"color": "red", "value": 1},
]}

PLAIN = {"mode": "absolute", "steps": [{"color": "green", "value": None}]}

_id = [0]


def nid():
    _id[0] += 1
    return _id[0]


def target(expr, legend=None, instant=False, fmt=None, ref="A"):
    t = {
        "datasource": DS, "editorMode": "code", "expr": expr, "refId": ref,
        "instant": instant, "range": not instant,
    }
    if legend is not None:
        t["legendFormat"] = legend
    if fmt:
        t["format"] = fmt
    return t


def targets(specs, instant=False, fmt=None):
    return [
        target(expr, legend, instant=instant, fmt=fmt, ref=chr(ord("A") + i))
        for i, (expr, legend) in enumerate(specs)
    ]


def gp(x, y, w, h):
    return {"h": h, "w": w, "x": x, "y": y}


def timeseries(title, specs, pos, unit=None, desc="", stack=False, minval=None,
               maxval=None, custom=None, mappings=None):
    cust = {
        "drawStyle": "line", "lineInterpolation": "linear", "lineWidth": 1,
        "fillOpacity": 40 if stack else 15, "showPoints": "never",
        "spanNulls": True, "axisBorderShow": False, "axisCenteredZero": False,
        "gradientMode": "none", "pointSize": 5,
        "scaleDistribution": {"type": "linear"},
        "stacking": {"group": "A", "mode": "normal" if stack else "none"},
        "thresholdsStyle": {"mode": "off"},
    }
    if custom:
        cust.update(custom)
    defaults = {
        "color": {"mode": "palette-classic"},
        "custom": cust,
        "mappings": mappings or [],
        "thresholds": PLAIN,
    }
    if unit:
        defaults["unit"] = unit
    if minval is not None:
        defaults["min"] = minval
    if maxval is not None:
        defaults["max"] = maxval
    return {
        "type": "timeseries", "title": title, "description": desc,
        "id": nid(), "datasource": DS, "gridPos": pos,
        "fieldConfig": {"defaults": defaults, "overrides": []},
        "options": {
            "legend": {"calcs": ["lastNotNull", "max"], "displayMode": "table",
                       "placement": "bottom", "showLegend": True},
            "tooltip": {"mode": "multi", "sort": "desc"},
        },
        "targets": targets(specs),
    }


def stat(title, specs, pos, unit=None, mappings=None, thresholds=None, desc="",
         colormode="value", textmode="auto", graphmode="none", decimals=None,
         no_value=None):
    defaults = {
        "color": {"mode": "thresholds"},
        "mappings": mappings or [],
        "thresholds": thresholds or PLAIN,
    }
    if unit:
        defaults["unit"] = unit
    if decimals is not None:
        defaults["decimals"] = decimals
    if no_value is not None:
        # Beats a bare "No data" when an empty result is itself the answer.
        defaults["noValue"] = no_value
    return {
        "type": "stat", "title": title, "description": desc,
        "id": nid(), "datasource": DS, "gridPos": pos,
        "fieldConfig": {"defaults": defaults, "overrides": []},
        "options": {
            "colorMode": colormode, "graphMode": graphmode, "justifyMode": "auto",
            "orientation": "auto", "textMode": textmode, "wideLayout": True,
            "reduceOptions": {"calcs": ["lastNotNull"], "fields": "", "values": False},
        },
        "targets": targets(specs, instant=True),
    }


def gauge(title, specs, pos, unit="percentunit", thresholds=None, desc="", maxv=1):
    return {
        "type": "gauge", "title": title, "description": desc,
        "id": nid(), "datasource": DS, "gridPos": pos,
        "fieldConfig": {"defaults": {
            "color": {"mode": "thresholds"},
            "mappings": [], "min": 0, "max": maxv, "unit": unit,
            "thresholds": thresholds or {"mode": "absolute", "steps": [
                {"color": "green", "value": None},
                {"color": "yellow", "value": 0.8},
                {"color": "red", "value": 0.9},
            ]},
        }, "overrides": []},
        "options": {
            "showThresholdLabels": False, "showThresholdMarkers": True,
            "reduceOptions": {"calcs": ["lastNotNull"], "fields": "", "values": False},
        },
        "targets": targets(specs, instant=True),
    }


def bargauge(title, specs, pos, unit=None, thresholds=None, desc="", maxv=None,
             display="basic"):
    # "basic" draws one solid bar coloured by the value's own threshold. "lcd" splits
    # the bar into segments coloured by position along the threshold scale, which makes
    # a perfectly healthy value look mostly red — avoid it for anything with
    # thresholds.
    defaults = {
        "color": {"mode": "thresholds"},
        "mappings": [], "min": 0, "thresholds": thresholds or PLAIN,
    }
    if unit:
        defaults["unit"] = unit
    if maxv is not None:
        defaults["max"] = maxv
    return {
        "type": "bargauge", "title": title, "description": desc,
        "id": nid(), "datasource": DS, "gridPos": pos,
        "fieldConfig": {"defaults": defaults, "overrides": []},
        "options": {
            "displayMode": display, "orientation": "horizontal",
            "showUnfilled": True, "valueMode": "color",
            "reduceOptions": {"calcs": ["lastNotNull"], "fields": "", "values": False},
        },
        "targets": targets(specs, instant=True),
    }


def table(title, specs, pos, keep, renames, desc="", overrides=None, mappings=None,
          sort_by=None, sort_desc=True, order=None, exclude=None):
    """Instant-query table.

    `keep` is a regex of the columns to retain, applied before the join. Filtering
    first is what stops duplicated label columns (Time, __name__, job, instance) from
    colliding and being silently renamed to "field 1"/"field 2" by joinByField.

    When joining several queries, give exactly one of them the descriptive labels and
    reduce the others with `max by (<join field>) (...)` so nothing collides.
    """
    transformations = [
        {"id": "filterFieldsByName", "options": {"include": {"pattern": keep}}},
    ]
    if len(specs) > 1:
        join_field = renames.get("__join__", "dataset")
        transformations.append(
            {"id": "joinByField", "options": {"byField": join_field, "mode": "outer"}}
        )
    transformations.append({"id": "organize", "options": {
        # A synthetic join key built with label_join() has to survive `keep` so the
        # join can use it, but should not be shown; drop it here.
        "excludeByName": {name: True for name in (exclude or [])},
        # indexByName keys are the *original* field names, before renameByName runs.
        "indexByName": {name: i for i, name in enumerate(order or [])},
        "renameByName": {k: v for k, v in renames.items() if k != "__join__"},
    }})
    if sort_by:
        transformations.append(
            {"id": "sortBy", "options": {"fields": {},
                                         "sort": [{"field": sort_by,
                                                   "desc": sort_desc}]}}
        )
    return {
        "type": "table", "title": title, "description": desc,
        "id": nid(), "datasource": DS, "gridPos": pos,
        "fieldConfig": {"defaults": {
            "color": {"mode": "thresholds"},
            "mappings": mappings or [],
            "custom": {"align": "auto", "cellOptions": {"type": "auto"},
                       "inspect": False, "filterable": True},
            "thresholds": PLAIN,
        }, "overrides": overrides or []},
        "options": {"showHeader": True, "cellHeight": "sm",
                    "footer": {"show": False, "reducer": ["sum"], "countRows": False,
                               "fields": ""}},
        "targets": targets(specs, instant=True, fmt="table"),
        "transformations": transformations,
    }


def row(title, y, collapsed=False, children=None, repeat=None):
    """A dashboard row.

    Grafana keeps a *collapsed* row's children nested inside the row panel, and an
    *expanded* row's children at the top level. Getting that backwards makes panels
    vanish, so callers pass `children` only for collapsed rows.

    `repeat` names a template variable; Grafana then duplicates the row and everything
    under it once per value of that variable.
    """
    r = {
        "type": "row", "title": title, "id": nid(),
        "gridPos": gp(0, y, 24, 1),
        "collapsed": collapsed,
        "panels": children or [],
    }
    if repeat:
        r["repeat"] = repeat
        r["repeatDirection"] = "h"
    return r


# Which editor tab Grafana opens the variable on. Only the UI reads this: at query time
# PrometheusVariableSupport.query() takes the `query` string and hands it straight to
# PrometheusMetricFindQuery, which re-parses it. Derive it so the two cannot disagree.
QRY_TYPES = {"label_names(": 0, "label_values(": 1, "metrics(": 2, "query_result(": 3}


def query_var(name, query, label=None, multi=True, include_all=True, all_value=".*",
              current_all=True, hide=0, regex=None):
    """A Prometheus-backed template variable.

    `regex` filters and rewrites the returned strings. Named capture groups `value` and
    `text` split one string into what queries substitute and what the UI shows -- nest
    them (`(?<text>(?<value>\\S+) .*)`) to show a superset of what you select on.

    `label_values(...)` resolves against /api/v1/label/<l>/values over the *dashboard's
    time range*, so it lists every value seen in that window, not the ones that exist
    now. `query_result(...)` is an instant query at the range's end instead. Prefer it
    whenever a stale option would be actively wrong rather than merely extra.
    """
    v = {
        "name": name,
        "label": label or name,
        "type": "query",
        "datasource": DS,
        "query": {"qryType": QRY_TYPES.get(query.split("(")[0] + "(", 4), "query": query,
                  "refId": "PrometheusVariableQueryEditor-VariableQuery"},
        "refresh": 1,
        "includeAll": include_all,
        "multi": multi,
        "options": [],
        "sort": 1,
        "hide": hide,
        "regex": regex or "",
    }
    if include_all:
        v["allValue"] = all_value
    if current_all and include_all:
        v["current"] = {"text": ["All"], "value": ["$__all"]}
    return v


def dashboard(title, uid, description, panels, variables, tags, refresh="1m",
              time_from="now-24h"):
    return {
        "title": title,
        "uid": uid,
        "description": description,
        "tags": tags,
        "timezone": "browser",
        "schemaVersion": 41,
        "version": 1,
        "editable": True,
        "graphTooltip": 1,
        "refresh": refresh,
        "time": {"from": time_from, "to": "now"},
        "templating": {"list": variables},
        "annotations": {"list": [{
            "builtIn": 1, "datasource": {"type": "datasource", "uid": "grafana"},
            "enable": True, "hide": True, "iconColor": "rgba(0, 211, 255, 1)",
            "name": "Annotations & Alerts", "type": "dashboard",
        }]},
        "panels": panels,
    }